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X-ray structure and investigation of molecular motions by dielectric, vibrational and 1H NMR methods for two organic-inorganic hybrid piperazinium compounds: (C4H12N2)2[Sb2Cl10]·2H2O and (C4H12N2)2[Sb2Br10]·2H2O
Accepted Manuscript Title: X-ray structure and investigation of molecular motions by dielectric, vibrational and 1 H NMR methods for two organic-inorganic hybrid piperazinium compounds: (C4 H12 N2 )2 [Sb2 Cl10 ]·2H2 O and (C4 H12 N2 )2 [Sb2 Br10 ]·2H2 O Authors: Marcin Moskwa, Gra˙zyna Bator, Anna Piecha-Bisiorek, Ryszard Jakubas, Wojciech Medycki, Agnieszka Ci˙zman, Jan Baran PII: DOI: Reference:
S0025-5408(17)33154-9 https://doi.org/10.1016/j.materresbull.2018.03.048 MRB 9929
To appear in:
MRB
Received date: Revised date: Accepted date:
14-8-2017 9-3-2018 26-3-2018
Please cite this article as: Moskwa M, Bator G, Piecha-Bisiorek A, Jakubas R, Medycki W, Ci˙zman A, Baran J, X-ray structure and investigation of molecular motions by dielectric, vibrational and 1 H NMR methods for two organic-inorganic hybrid piperazinium compounds: (C4 H12 N2 )2 [Sb2 Cl10 ]·2H2 O Materials Research Bulletin (2010), and (C4 H12 N2 )2 [Sb2 Br10 ]·2H2 O, https://doi.org/10.1016/j.materresbull.2018.03.048 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
X-ray structure and investigation of molecular motions by dielectric, vibrational and 1H NMR methods for two organic-inorganic hybrid
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piperazinium compounds: (C4H12N2)2[Sb2Cl10]·2H2O and (C4H12N2)2[Sb2Br10]·2H2O
Marcin Moskwaa, Grażyna Batora, Anna Piecha-Bisioreka*, Ryszard Jakubasa, Wojciech Medyckib, Agnieszka Ciżmanc and Jan Barand
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wrocław, Poland.
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Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland.
Division of Experimental Physics, Wroclaw University Science and Technology, Wybrzeże Wyspiańskiego 27, 50-
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370 Wrocław, Poland.
Institute of Low Temperatures and Structural Research, Polish Academy of Sciences, Okólna 2, 50-422, Wrocław,
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*Corresponding Author
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Poland.
E-mail address: [email protected] (Anna Piecha-Bisiorek)
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Graphical abstract
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Highlights Bis(piperazine-1,4-diium) decabromodiantimonate(III) (PSB) dihydrate has been synthesized and characterized;
The structural phase transition for PSB at ca. 50 K has been confirmed by the dielectric and 1H NMR spectroscopy results.
The molecular dynamic motion parameters of the organic cations and water molecules have been evaluated and compared for PSB and PSC
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ABSTRACT
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Bis(piperazine-1,4-diium) decabromodiantimonate(III) dihydrate, (C4H12N2)2[Sb2Br10]·2H2O, (abbreviated as PSB) has been synthesized and characterized by single-crystal X-ray diffraction studies. The obtained results indicate that PSB is isostructural with a recently described chloride analogue, (C4H12N2)2[Sb2Cl10]2H2O (PSC), crystallizing with R2MX5·nH2O stoichiometry and characterized by the discrete zero-dimensional anionic species. The crystal structure of PSB is described by monoclinic symmetry in a P21/n space group. Dielectric measurements (down to 25 K) and IR spectral analyses (measured over a broad temperature range) suggested a much more complicated phase situation below 80 K than for that of PSC. To verify and compare the molecular motions of the organic cations in both analogues, a proton magnetic resonance (1H NMR) technique was also applied.
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1. Introduction
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KEYWORDS: piperazine-1,4-diium; phase transition; dielectric; 1H NMR; IR.
The conscious synthesis and design of organic-inorganic hybrid materials based on divalent or
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trivalent metal halides has attracted scientific attention due not only to the interesting structural topologies of these compounds but also to their unique chemical and physical properties as well
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as possible novel applications in optoelectronics, data communication, switchable dielectric devices and rewritable optical data storage [1-3].
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The family of organic haloantimonate(III)/halobismuthate(III) hybrids, defined by the general
formula RaMbX(3b+a) (where X = Cl, Br or I; M = Sb(III) or Bi(III); and R is an organic cation), have a tendency to constitute discrete (mono-) or polyoctahedral anions in the crystalline state, where the basic MX6 octahedral units are connected either by corners, edges or by faces. These systems usually form zero- (0D), one- (1D), two- (2D) or sparsely three-dimensional (3D) inorganic networks [4, 5]. It is interesting that the ferroelectric properties in this group of
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compounds have been limited only to few chemical stoichiometries, namely, R5M2X11 [6-10], R3M2X9 [11-13], RMX4 [14,15] and R2MX5 [16-19]. The anionic framework of R5M2X11 compounds is characterized by the presence of the discrete (0D) dioctahedral units [M2X11]5-, whereas the nonlinear electric properties among R3M2X9 compounds were reported only for the compounds with 2D anionic layers. Regarding the remaining two compound types (RMX4 and
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R2MX5), ferroelectric properties were observed for the crystals built up of the 1D anionic
substructure with cis or trans geometry of the [MX5]2- chains. It is worth noting that paraelectricferroelectric phase transitions (PTs), found in the R5M2X11, R3M2X9, RMX4 and in the majority of R2MX5 stoichiometries (e.g., (MV)[BiBr5] [17] (where MV is the methyl viologen dication), (C3N2H5)2[SbCl5] [18] or (C2H5NH3)2[BiCl5] [19] appear due to a distortion of the trans- or cisconnected octahedra leading to the strong polar polyanionic substructures (“displacive”
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contribution).
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Very recently, Sghaier et al. [20] have reported the first example of an organic-inorganic piperazine-1,4-diium hybrid: (C4H12N2)2[Sb2Cl10]2H2O (abbreviated PSC) which crystallized as
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R2MX5 and was characterized by discrete 0D anionic sublayers. For crystals of PSC, the was not observed for this compound.
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ferroelectricity was postulated to appear below 70 K. The ferroelectric hysteresis loop, however,
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In this paper, we report the synthesis, crystal structure, dielectric and vibrational studies of
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bis(piperazine-1,4-diium) decabromodiantimonate(III) dihydrate, (C4H12N2)2[Sb2Br10]·2H2O (PSB) in addition to the vibrational properties of PSC. The molecular motions of the organic cations are studied by means of proton magnetic resonance (1H NMR) for both piperazinium
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analogues. The molecular mechanism of the structural PTs in PSB and PSC is also proposed.
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2. EXPERIMENTAL DETAILS Synthesis of the complexes
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Starting materials for the synthesis of piperazinium-1,4-diium haloantimonates(III), PSB and
PSC, were obtained from commercial sources: (Sigma-Aldrich) Sb2O3 (99.99%), C4H10N2·6H2O (98%), HBr (48%), HCl (37%) and SbBr3 (99.9%) (ABCR). An aqueous solution of piperazine was added to solutions of Sb2O3 or SbBr3 dissolved in concentrated HCl or HBr. After few days, the polycrystalline materials were formed by slow evaporation from solution. The polycrystalline solids were recrystallized and characterized by
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elemental analysis: PSB: C: 7.88%, N: 4.64%, and H: 2.17% (calc. C: 7.66%, N: 4.47%, and H: 2.25%); PSC: C: 12.03%, N: 6.95%, and H: 3.51% (calc. C: 11.86%, N: 6.91%, and H: 3.48%). The purity of the PSB was verified by XRD (see Figure S1-Supplementary Materials). Thermal analysis Simultaneous thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were
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carried out on a Setaram SETSYS 16/18 instrument from 300-900 K with a ramp rate of 5 K·min-1 under nitrogen (flow rate: 1 dm3·h-1). X-ray diffraction analysis
Single-crystal X-ray diffraction data for PSB were collected at 80 K on an Agilent
Technologies Xcalibur, Ruby к-axis four-circle diffractometer equipped with an Oxford
Cryosystem cooler using graphite monochromated MoKαradiation. The structure was solved by
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direct methods with the SHELXS-2014/7 [21] program and refined by the full-matrix least-
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squares methods on all F2 data using SHELXL-2014/7 [22]. Data collection was performed by using CrysAlis CCD; reduction was executed on CrysAlis Pro [23]. All non-hydrogen atoms
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were refined anisotropically. H atoms attached to O and N atoms were found in a difference
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Fourier map. Water H atoms and N-bound H atoms were refined with O─H, H···H, N─H, H···H distances restrained to 0.850(2), 1.380(2), 0.900(2), 1.450(2) Å, respectively. H atom isotropic
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temperature factors were assumed as 1.2 times Ueq(N) and 1.5 times Ueq(O). Water H and N-
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bound H atoms were then constrained to ride on their parent atoms (AFIX 3 instruction in SHELXL-2014/7) [22]. C-bound H atoms were set as a riding model, and their isotropic temperature factors were assumed to be 1.2 times Ueq. The crystal data together with
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experimental and refinement details are given in Table 1. Crystallographic data for the structure reported in this paper (excluding structures factors) have been deposited with the CCDC No.
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1564229.
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Dielectric measurements Two different methods were applied for the dielectric measurements of PSB. The complex
value of dielectric permittivity, ε* = ε’ - iε’’ was first measured using an Agilent E4980A Precision LCR Meter in the frequency range between 135 Hz and 2 MHz and in the temperature range between 85–310 K. The other type of measurement was obtained using an Alpha-A High Resolution Dielectric Modular Measurements System (Novocontrol) assisted by a LakeShore
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temperature controller. The dielectric measurements were performed as a function of frequency from 10 Hz and to 10 MHz. The temperature of the sample between 25 K and 100 K was maintained by a jet of pure helium; the temperature control was better than 0.5 K. In both experiments, the polycrystalline material was used in the form of pressed pellets. The diameter of the pellets was 10 mm, and the thickness was 1 mm. The overall error in the estimation of the
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real part of dielectric permittivity value was less than 5%. The silver electrodes were painted on both opposing faces of the pellets. Infrared studies
The infrared spectra of PSB and PSC (suspension in Nujol between CsI windows) were
measured with a Bruker IFS-88 spectrometer from 4000-400 cm-1 in a wide temperature range (12–296 K) with a resolution of 2 cm-1 (see Figure S2a and b). An APD Cryogenics Displex
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Closed Cycle Refrigeration System, model CSW-202, was used for the temperature dependent
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studies. The temperature of the sample was maintained with an accuracy of 0.1 K by a Scientific Instruments INC controller Series 5500. The Grams Galactic Industries program was used for a
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numerical fitting of the experimental data. The Gaussian functions were used for fitting the shape
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of the infrared bands. Powder FT-Raman were recorded on an FRA-106 attached to a Bruker IFS-88 using a Nd:YAG diode pump laser. The measurements were performed at room
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temperature over a wavenumber range of 3500-80 cm-1 with resolution better than 2 cm-1. Table
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S1 summarizes the observed positions of the bands in the IR and Raman spectra along with their assignments. The assignments of the internal modes of the organic cation for compounds containing piperazine were used as guides [24-28]. The observed Raman and IR bands between
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400 and 50 cm-1 are tentatively assigned to the internal modes of the [Sb2Br10]4- and [Sb2Cl10]4anions on the basis of comparison with other studies carried out on numerous
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haloantimonates(III) [29].
Proton magnetic resonance (1H NMR)
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NMR measurements were made using an ELLAB TEL-Atomic PS 15 (operating at 25 MHz at
temperatures from room temperature down to 77 K) and a Tecmag Scout (operating at 24.8 MHz at temperatures below liquid nitrogen) spectrometers. The spin-lattice relaxation times, T1, were measured using a saturation sequence of π /2 pulses followed by a variable time interval, τ, and a reading π /2 pulse. The magnetization recovered exponentially within experimental error at all temperatures. The temperature of the sample was adjusted by liquid nitrogen cooling and was
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controlled by a UNIPAN 660 temperature controller operating with a Pt 100 sensor, providing extended temperature stability better than 1 K. Below temperatures of liquid nitrogen a helium cooled Leybold cryostat was applied. The powdered sample of PSB/PSC was evacuated at room temperature and then sealed under vacuum in a glass ampoule. All measurements were made upon heating the sample. The errors in the measurements of T1 were estimated to be
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approximately 5%. 3. Results and discussion 3.1 Thermal analysis
Thermal stability of PSB was studied by means of TGA and DTA. The result for PSB shows
that the compound is stable up to ca. 360 K (Figure S3). On the DTA curve, a small, broad peak
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corresponding to an endothermal effect between 360 and 460 K was assigned to the loss of two
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water molecules per formula unit of the crystal. It should be noted that the mass loss on the order
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of ca. 3% is probably related to the complete dehydration process (2.87% of water in the title compound). Further heating showed two endothermic peaks on the DTA curve at ca. 530 and
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580 K. Heating above ca. 600 K leads to sample decomposition.
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3.2 X-ray
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PSB crystallizes in the monoclinic system in P21/n (No. 14) space group and is isomorphous with a PSC analogue reported previously [20]. In the asymmetric part of the unit cell, there is
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one piperazinium-1,4-diium dication, half of a discrete decabromodiantimonate(III) anion and one water molecule. The view of the independent part and numbering scheme for PSB are presented in Figure 1.
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In the PSB crystal, the SbBr6 octahedra are combined in pairs by two bridging Br atoms giving
rise to centrosymmetric binuclear [Sb2Br10]4- anions with a Sb(1)−Br(3)−Sb(1)i angle of
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86.80(2)°. Sb−Br distances fall into two ranges: from ~2.6–2.9 Å for the terminal Br atoms and from ~3.1–3.3 Å for the bridging ones (Table 2). The longest terminal distance of 2.870(4) Å for Sb(1)−Br(1) was due to the presence of two hydrogen bonds between Br and H atoms; the latter atom belonging to either the N atoms of the organic groups or the O atoms of water molecules. The bridging Sb(1)−Br(3) and Sb(1)−Br(3)i bonds (3.066(3) Å and 3.256(4) Å, respectively) lie opposite to the trans Sb−Br terminal bonds (Sb(1)−Br(4), 2.574(2) Å; Sb(1)−Br(5), 2.629(3) Å).
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The trans Sb−Br terminal bonds are shorter than the remaining Sb−Br bonds (2.711(2) Å for Sb(1)−Br(2) and 2.870(4) Å in the case of Sb(1)−Br(1)). The bonds and angles within the [Sb2Br10]4- anion are listed in Table 2. The characteristic feature of the PSB crystal was the presence of the infinite, two-dimensional hydrogen bond system perpendicular to the ac-axis resulting from the interaction between the [Sb2Br10]4- anions and water molecules (see Figure 2).
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As shown in Figure 3a, the cations are stacked in the substructure channels created by
binuclear [Sb2Br10]4- anions along the [-10-1] direction. The organic groups, present as dications, have a chair conformation. The same conformation of the dication moieties was observed in the PSC structure [20]. Water molecules are the proton acceptors in the moderately strong N−H···O type hydrogen bonds (Table 3) as illustrated in Figure 3b.
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3.3 Dielectric measurements
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Recently, reported dielectric studies on PSC revealed relaxation processes in the kilohertz frequency region when approaching the PT temperature (Tc=70 K) [20]. This was a motivation to
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carry out the dielectric measurements for PSB in wide frequency and temperature ranges as well.
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The main purpose of this study was to check if the enormous increase of ’, similar as for PSC, could be observed for PSB.
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Temperature dependencies of the complex electric permittivity of PSB measured at selected
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frequencies are shown in Figure 4. Two relaxation processes were detected from 80–310 K and between 85–175 K for relaxators 1 and 2, respectively. The dielectric increment, o for the latter process is small ( was below 0.2), while the former is characterised by a larger
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increment = 3.
High temperature dielectric relaxation processes are well-described by the Cole-Cole equation
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with a single relaxation time:
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* 'i ' ' 1
0 1 , 1 1 i 1
(1)
where o and are the low and high frequency limits of electric permittivity, respectively;
corresponds to the angular frequency, is the macroscopic relaxation time and is the distribution of the relaxation time parameter.
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The Cole-Cole diagrams at four selected temperatures for relaxator 1 are depicted in Figure 5. The estimated value of the parameter is 0.2. The activation energy, EA,diel1, can be estimated directly from the Arrhenius equation for the dielectric relaxation time:
E A , diel1 , RT
1 01 exp
(2)
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where o1 is the high temperature limit of the relaxation time, R – gas constant 8.314 J/mol·K and T – absolute temperature.
The EA,diel1 value for relaxator 1 of PSB was approximately 353 kJ/mol (Figure S4). Activation energy values such as that are typical for dielectric processes found in other
haloantimonate(III) and halobismuthate(III) crystals containing bulky organic cations[30-33]. The activation energy for relaxator 2 was 312 kJ/mol. The macroscopic relaxation time for
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relaxator 2 was estimated from the maxima of the imaginary parts, ’’, of the electric permittivity
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(Figure 4b). It should be noted that the values, estimated from the Cole-Cole equation for
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relaxator 1, are on the order of 19-21, which are still relatively high. This may indicate an
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additional high frequency dielectric relaxation process over this temperature range. Taking into account the results reported by Sghaier et al. [20], we measured the complex
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dielectric permittivity below 80 K using an Alpha-A High Resolution Dielectric Modular Measurements System (Novocontrol) with a pellet placed in the cell under high vacuum. The
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dielectric response function strongly depends on the quality of the polycrystalline sample and measurement conditions. Samples kept in the measurement cell under vacuum lose water
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molecules. That means such a sample should be treated as a defective material. Measurements were carried out under different experimental conditions. The samples, which were previously
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measured under vacuum, showed an essentially different response than those measured under ambient pressure with a nitrogen atmosphere. It proved that the observed difference in the dielectric response, between the samples measured under vacuum and ambient pressure, may be
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explained in terms of water molecule loss. As seen in Figure 6a, ’ increases continuously over the analysed temperature region and exhibits weak anomalies at ca. 80, 50 and 30 K. It is interesting that between 100 and 25 K, another relaxation process was observed (Figure 6b) with a dielectric increment, , of ca. 0.6. It should be noted that in order to confirm the polar character of the lowest temperature phase of
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PSB (below 50 K) the measurements of the pyroelectric current should be carried out. Such behaviour is characteristic of quantum ferroelectrics, e.g., SrTiO3 [34]. We concluded that this may be treated as a potential quantum ferroelectric, since we cannot exclude the ferroelectric properties of PSB.
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3.3 Spectroscopic studies
To confirm the presence of PT in PSB as well as to analyse the role of the piperazine-1,4-
diium dication and water molecules in the molecular mechanism of the low-temperature PTs in both compounds, IR spectra at various temperatures were measured (see Figures S2a and S2b). It should be emphasized that the changes in positions, in intensities as well as of FWHM (full
width at half maximum) found for PSC and PSB are very subtle and may indicate the continuous
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nature of the structural anomalies. It is noteworthy that the changes in the positions of selected
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bands for PSC are smaller than those of PSB. This is most likely due to the strong Christiansen effect [35, 36].
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The most pronounced anomalies are visible from 3680 and 3370 cm-1, where bands arising from
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the ν(OH) and ν(NH) vibrations (Figures 7a and 8a) appear. For PSB, four well-separated components can be distinguished at low temperature, which shift continuously towards higher
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wavenumbers during the heating cycle. Around the PT point (50 K), an insignificant change in
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the positions of all bands analysed was observed (see Figure 7b); two of them (denoted as 2 and 3) subsequently disappear at 125 and 250 K, respectively. The PSC results were very similar (Figure 8b); four well-shaped bands are visible and undergo a weak anomaly related to the
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structural PT at 70 K. One of the bands (No. 4) vanished at approximately 225 K while the shoulder, depicted as 2, appeared a few degrees below and vanished a few degrees above Tc. It
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should be stressed, however, that during heating of both PSB and PSC samples, a significant decrease in the intensities of all analysed bands was observed.
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The temperature evolutions of the PSB and PSC bands observed between 3200 and 3050 cm-1
and assigned to the νas(NH) and νs(NH) vibrations are presented in Figures 9 and 10, respectively. The detailed analyses of this frequency region, especially for the bromide (PSB) analogue, was very difficult to observe due to the Christiansen effect mentioned above. For PSB, we observed at least four bands at the lowest temperature, the bandwidths of which were the smallest and increased significantly upon heating the sample. The positions of these bands are almost
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temperature independent; nevertheless, some signatures of PT at 50 K are visible (Figure 9b). For the PSC compound, the IR spectra at low temperatures are much more complicated and featured by eight bands, four of which create characteristic shoulders which disappeared at different temperatures (Figure 10b). The PT at 70 K is clearly visible mainly as a change in the slope of the = f(T) curves.
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The observed changes in the IR spectra may indicate the participation of the organic dications in the mechanisms of the PT found for both PSC and PSB crystals; however, their contribution is weakly reflected.
3.5 Proton magnetic resonance (1H NMR)
The temperature dependencies of the proton nuclear spin-lattice relaxation time, T1, for the
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PSC and PSB compounds are shown in Figure 11. We distinguished four different temperature
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ranges for T1 runs observed for both compounds. In the lowest temperature range (T 40 K) the
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spin-lattice relaxation times, T1, remained constant. The next temperature range, between 40 K and ca. 110 K, a double minimum was observed for both compounds. Then, up to 240 K, the T1
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value increased and reached maximum values at 221 K and 243 K for PSB and PSC, respectively. The fourth temperature range, above 240 K, the observed T1 value for both
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compounds strongly decreased and reached the minimum for one of them (PSB T1min=37 ms at
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420 K). It should be noted that between 157 and 290 K, we observed two components of T1, long
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and short.
Furthermore, the T1 vs. 1/T curve for PSB reveals a rapid anomaly at ca. 50 K, which confirmed the structural PT suggested from dielectric measurements. A similar anomaly on the
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T1(1/T) curve was observed for PSC near 65 K and was in a good agreement with the dielectric studies reported in [20].
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When analysing the possible mechanisms of proton relaxation in the compounds under
investigation, we may consider the following types of molecular interactions and motions as the temperature increases: - interactions of protons, from either cations or water molecules, with the neighbouring quadrupolar halogens, Cl and Br, – jumps of protons in hydrogen bonds,
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– motions of water molecules (180° flip), – reorientations of the piperazine cations (libration, 180° flip), – reorientations of the piperazine cations around the pseudo six-fold symmetry axes (C6’). At the lowest temperatures, analogous to previously studied compounds containing halogen atoms, the first possibility has to be taken into account, i.e., a domination of the quadrupole
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interactions [37-39]. In the next temperature region (above 40 K), the observed double minimum may be a result of the active proton jumps within the hydrogen bonds of both compounds. One possible hydrogen bond is formed between a proton of the cation (primarily from the nitrogen) and a halogen atom (Cl or Br). The other hydrogen bond may appear between a proton from a
water molecule and a halogen in the anionic species. The T1 temperature dependencies may be fitted using the BPP theory equation [40]:
(3)
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C1 C2 4 C1 4 C 2 1 C2 , C1 2 2 2 2 2 2 2 2 T1 1 0 C1 1 40 C1 1 0 C 2 1 40 C 2
where C1 and C2 are relaxation constants, c1 and c2 are the correlation times assigned to the
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protons jumps of the two different types of hydrogen bonds. The temperature dependence of the correlation times in this temperature region is well described by the Arrhenius law
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ci=oiexp(Ea/RT).
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The two next temperature regions, above and below 240 K, are assigned to the gradual release of the piperazinium cation motions (long time component), whereas we ascribe the short
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component of T1 to the relaxation processes caused by the reorientation of the water molecules [20]. The parameters of the fitting procedure applied to the corresponding minima and slopes of the experimental T1 temperature dependencies for PSC and PSB are collected in Table S3. It
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should be noted that the relatively large activation energy above ca. 300 K for both compounds (35 kJ/mol – PSB, 21 kJ/mol – PSC) is characteristic either of the overall or the C6’–type
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reorientation motions of these bulky cations. 4. Conclusion PSB crystallizes in the monoclinic system with P21/n space group and is isomorphic with the previously reported PSC analogue [20]. The crystal structure of PSB (at 80 K) contains one ordered piperazinium-1,4-diium dication, half of a discrete decabromodiantimonate(III) anion
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and a water molecule. In spite of their structural similarities, the dielectric properties of the two crystals in this study were significantly different, especially below 100 K. The dielectric response for PSC resembled that encountered in the ferroelectric crystals, whereas the dielectric anomaly of PSB was quite weak and typical of a non-ferroelectric PT. However, it does not exclude the presence of polar phase at the lowest temperatures. For the latter analogue, we
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address structural PT at ca. 50 K, which was confirmed by dielectric and 1H NMR spectroscopy results. The vibrational (IR) studies on PSB and PSC showed that the low temperature PTs were weakly reflected in the temperature dependent infrared spectra, which indicated that the
dynamics of the organic cations is not crucial in the PT mechanism. The visible anomalies on the T1 vs. 1/T curves at approximately 70 K for PSC and 50 K for PSB indicated that proton motions may play an important role within the various types of hydrogen bonds.
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The measurements of the spin-lattice relaxation times for PSB and PSC over a wide
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temperature region (10 – 430 K) allowed us to propose the following molecular motions in different temperature ranges:
In the temperature range below 40 K, the quadrupole interactions dominate;
Between 40 and 110 K, the double minima of T1 are assigned to the proton jumps along
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the hydrogen bonds, which are expected to contribute to the phase transition Above 110 K, the piperazinium cation reorients in a successive way (from libration to
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mechanism of both analogues; overall reorientation);
From 160–290 K, the water molecules relax independently.
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ACKNOWLEDGEMENT This work has been supported by the Polish Ministry of Science and Higher Education Agreement Nr 3580/ZIBJ DUBNA/2016/0 and partially by the International Program ZIBJ
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Dubna №04-4-1121-2015/2017.
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References [1]
J. F. Scott, Applications of modern ferroelectrics., Science. 315 (2007) 954–959. DOI:10.1126/science.1129564.
[2]
S.T. Han, Y. Zhou, V.A. Roy, Towards the development of flexible non-volatile memories, Adv. Mater. 25 (2013) 5425–5449. DOI:10.1002/adma.201301361. J. Li, J. Claude, L.E. Norena-Franco, S.I. Seok, Q. Wang, Electrical energy storage in
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[3]
ferroelectric polymer nanocomposites containing surface-functionalized BaTiO3 nanoparticles, Chem. Mater. 20 (2008) 6304–6306. DOI:10.1021/cm8021648. [4]
L. Sobczyk, R. Jakubas, J. Zaleski, Self-assembly of Sb(III) and Bi(III) halo-coordinated octahedra in salts of organic cations. Structure, properties and phase transitions., Pol. J. Chem. 71 (1997) 265–300.
W. Zhang, R.-G. Xiong, Ferroelectric metal-organic frameworks, Chem. Rev. 112 (2012)
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[5]
J. Lefebvre, P. Carpentier, R. Jakubas, L. Sobczyk, The para-ferroelectric phase transition
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[6]
N
1163–1195. DOI:10.1021/cr200174w.
in (NH3CH3)5Bi2Cl11 (P.M.A.C.B.), Phase Transitions. 33 (1991) 31–41. [7]
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DOI:10.1080/01411599108207709.
R. Jakubas, A. Piecha, A. Pietraszko, G. Bator, Structure and ferroelectric properties of
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(C3N2H5)5Bi2Cl11, Phys. Rev. B. 72 (2005) 104107-1–8. [8]
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DOI:10.1103/PhysRevB.72.104107. A. Piecha, A. Pietraszko, G. Bator, R. Jakubas, Structural characterization and ferroelectric ordering in (C3N2H5)5Sb2Br11, J. Solid State Chem. 181 (2008) 1155–1166. [9]
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DOI:10.1016/j.jssc.2008.02.029. A. Piecha, A. Białońska, R. Jakubas, Structure and ferroelectric properties of
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[C3N2H5]5[Bi2Br11], J. Phys. Condens. Matter. 20 (2008) 325224-1–9. DOI:10.1088/09538984/20/32/325224.
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[10] [11]
J. Jóźków, R. Jakubas, G. Bator, A. Pietraszko, Ferroelectric properties of (C5H5NH)5Bi2Br11, J. Chem. Phys. 114 (2001) 7239–7246. DOI:10.1063/1.1349897. R. Jakubas, G. Bator, L. Sobczyk, J. Mróz, Dielectric and pyroelectric properties of (CH3NH3)3Me2Br9 (Me = Sb, Bi) crystals in the ferroelectric phase transition regions, Ferroelectrics. 158 (1994) 43–48. DOI:10.1080/00150199408215991.
[12]
G. Bator, R. Jakubas, L. Sobczyk, J. Mróz, Dielectric and pyroelectric properties of
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[N(CH3)3H]3Sb2Cl9 in the low temperature region, Ferroelectrics 141 (1993) 177-187. DOI:10.1080/00150199308223445. [13]
M. Gdaniec, Z. Kosturkiewicz, R. Jakubas, L. Sobczyk, Structure and mechanism of ferroelectric phase transition in tris(dimethylammonium)-nonachlorodiantimonate(III), Ferroelectrics. 77 (1988) 31–37. DOI:10.1080/00150198808223224. R. Jakubas, Z. Ciunik, G. Bator, Ferroelectric Properties of [4-NH2C5H4NH][SbCl4]. Phys.
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[14]
Rev. B67 (2003) 024103-1–6. DOI:10.1103/PhysRevB.67.024103. [15]
G. Xu, Y. Li, W.-W. Zhou, G.-J. Wang, X.-F. Long, L.-Z. Cai, M.-S. Wang, G.-C. Guo, J.-S. Huang, G. Bator, R. Jakubas, A ferroelectric inorganic-organic hybrid based on NLO-phore stilbazolium, J. Mater. Chem. 19 (2009) 2179–2183. DOI:10.1039/B819473D.
M. Owczarek, P. Szklarz, R. Jakubas, A. Miniewicz, [NH2(C2H4)2O]MX5: a new family of
U
[16]
N
morpholinium nonlinear optical materials among halogenoantimonate(III) and halogenobismuthate(III) compounds. Structural characterization, dielectric and W. Bi, N. Leblanc, N. Mercier, P. Auban-Senzier, C. Pasquier, Thermally induced Bi(III)
M
[17]
A
piezoelectric properties., Dalton Trans. 41 (2012) 7285–7294. DOI:10.1039/c2dt30291h. lone pair stereoactivity: Ferroelectric phase transition and semiconducting properties of
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(MV)BiBr5 (MV = methylviologen), Chem. Mater. 21 (2009) 4099–4101. [18]
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DOI:10.1021/cm9016003.
A. Piecha-Bisiorek, A. Białońska, R. Jakubas, Novel organic–inorganic hybrid ferroelectric: bis(imidazolium) pentachloroantimonate(II), (C3N2H5)2SbCl5, J. Mater.
[19]
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Chem. 22 (2012) 333–336. DOI:10.1039/c1jm13597j. A. Piecha-Bisiorek, A. Gągor, R. Jakubas, A. Ciżman, R. Janicki, W. Medycki,
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Ferroelectricity in bis(ethylammonium) pentachlorobismuthate(III): synthesis, structure, polar and spectroscopic properties, Inorg. Chem. Front. 4 (2017) 1281–1286.
A
DOI:10.1039/C7QI00254H.
[20]
M.O.M. Sghaier, K. Holderna-Natkaniec, A. Wozniak-Braszak, P. Czarnecki, S. Chaabouni, Structure and internal dynamics of bis(piperazine-1,4-diium) pentachloroantimonate(III) monohydrate, Polyhedron. 79 (2014) 37–42. DOI:10.1016/j.poly.2014.04.030.
[21] G.M. Sheldrick, A short history of SHELX, Acta Crystallogr. Sect. A Found. Crystallogr.
14
64 (2007) 112–122. DOI:10.1107/S0108767307043930. [22] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem. 71 (2015) 3–8. DOI:10.1107/S2053229614024218. [23] CrysAlis CCD, CrysAlis Pro, Agilent Technologies, Version 1.171.37.31. [24] P. Hendra, D. Powell, The infra-red and Raman spectra of piperazine, Spectrochim. Acta.
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4408 (1962) 299–306. DOI:10.1016/S0371-1951(62)80138-6.
[25] S. Gunasekaran, B. Anita, Spectral investigation and normal coordinate analysis of piperazine, Indian J. Pure Appl. Phys. 46 (2008) 833–838.
[26] R.J. Obremski, C.W. Brown, E.R. Lippincott, Vibrational spectra of single crystals. polymorphic solids of cyclohexane, J. Chem. Phys. 49 (1968) 185–191. DOI:10.1063/1.1669807.
U
[27] H. Takahashi, T. Shimanouchi, K. Fukushima, T. Miyazawa, Infrared spectrum and
N
normal vibrations of cyclohexane, J. Mol. Spectrosc. 13 (1964) 43–56. DOI:10.1016/0022-2852(64)90053-0.
A
[28] R.G. Synder, J.H. Schachtschneider, A valence force field for saturated hydrocarbons,
M
Spectrochim. Acta. 21 (1965) 169–195. DOI:10.1016/0371-1951(65)80115-1. [29] H.L. Sheu, J. Laane, Trans effect in halobismuthates and haloantimonates revisited.
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molecular structures and vibrations from theoretical calculations, Inorg. Chem. 52 (2013)
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4244–4249. DOI:10.1021/ic302082a. [30] I. Płowaś, P. Szklarz, R. Jakubas, G. Bator, Structural, thermal and dielectric studies on the novel solution grown (4-dimethylaminopyridinium) chloroantimonate(III) and
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chlorobismuthate(III) crystals, Mater. Res. Bull. 46 (2011) 1177–1185. DOI:10.1016/j.materresbull.2011.04.013.
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[31] J. Zaleski, R. Jakubas, G. Bator, J. Baran, Dielectric dispersion, dilatometric and infrared studies of tris(guanidinium) enneachlorodiantimonate(III), J. Mol. Struct. 325 (1994) 95–
A
103. DOI:10.1016/0022-2860(94)80023-5.
[32] B. Bednarska-Bolek, J. Zaleski, G. Bator, R. Jakubas, On structural phase transitions in piperidinium halogenoantimonates(III) and bismuthates(III): X-ray, calorimetric, dilatometric, dielectric and Raman studies, J. Phys. Chem. Solids. 61 (2000) 1249–1261. DOI:10.1016/S0022-3697(99)00414-X. [33] P. Szklarz, J. Zaleski, R. Jakubas, G. Bator, W. Medycki, K. Falińska, The structure,
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phase transition and molecular dynamics of [C(NH2)3]3[Sb2Br9], J. Phys. Condens. Matter. 17 (2005) 2509–2528. DOI:10.1088/0953-8984/17/15/021. [34] S. E. Rowley, L. J. Spalek, R. P. Smith, M. P. M. Dean, M. Itoh, J. F. Scott, G. G. Lonzarich, S. S. Saxena, Ferroelectric quantum criticality, Nat. Phys. 10 (2014) 367–372. DOI:10.1038/NPHYS2924.
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[35] C. Christiansen, Untersuchungen über die optischen Eigenschaften von fein verteilten Körpern, Ann. Der Phys. Und Chemie. 23 (1884) 298–306.
[36] C. Christiansen, Untersuchungen über die optischen Eigenschaften von fein verteilten Körpern, Ann. Der Phys. Und Chemie. 24 (1885) 439–446.
[37] M. Węcławik, P. Szklarz, W. Medycki, R. Janicki, a. Piecha-Bisiorek, P. Zieliński, R.
Jakubas, Unprecedented transformation of [I−·I3−] to [I42−] polyiodides in the solid state:
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structures, phase transitions and characterization of dipyrazolium iodide triiodide, Dalt.
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Trans. 44 (2015) 18447–18458. DOI:10.1039/C5DT02265G. [38] M. Wojtaś, A. Gągor, O. Czupiński, A. Piecha-Bisiorek, D. Isakov, W. Medycki, R.
A
Jakubas, Polar and antiferroelectric behaviour of a hybrid crystal – piperazinium
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perchlorate, CrystEngComm. 17 (2015) 3171–3180. DOI:10.1039/C5CE00161G. [39] A. Piecha-Bisiorek, R. Jakubas, W. Medycki, M. Florek-Wojciechowska, M.
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Wojciechowski, D. Kruk, Dynamics of Ferroelectric Bis(imidazolium)
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Pentachloroantimonate (III) by Means of Nuclear Magnetic Resonance 1H Relaxometry and Dielectric Spectroscopy, J. Phys. Chem. A. 118 (2014) 3564–3571. DOI:10.1021/jp501331c.
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[40] N. Bloembergen, E.M. Purcell, R. V. Pound, Relaxation effects in nuclear magnetic
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resonance absorption, Phys. Rev. 73 (1948) 679–712. DOI:10.1103/PhysRev.73.679.
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Figure captions
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Figure 1. The asymmetric unit of the PSB crystal structure showing the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability. Transparent part completes the chemical formula of PSB. Symmetry code is given in Table 2.
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Figure 2. Projection of the crystal structure of PSB, which illustrates the geometry of the hydrogen bond system.
Figure 3. Projection of the PSB crystal structure viewed along a) [-10-1] and b) [100] direction. A polyhedral representation is used for the [Sb2Br10]4- bioctahedron. Dashed lines in part b indicate selected hydrogen bonds.
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A
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Figure 4. Temperature dependence of a) the real (ε’) and b) imaginary (ε’’) parts of the complex dielectric constant (ε*) measured for the powder sample of PSB crystal upon heating.
Figure 5. Cole-Cole plots at several temperatures (relaxator 1).
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A
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Figure 6. Temperature dependence of a) the real (ε’) and b) imaginary (ε’’) parts of the complex dielectric constant (ε*) measured for the powder sample of PSB upon cooling below 100 K.
Figure 7. a) Temperature evolution of the IR spectra for PSB in the νas(H2O), νs(H2O) and ν(NH) vibrations region (3680−3350 cm-1), b) the wavenumber positions of the bands at selected temperatures between 13 and 296 K.
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A
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Figure 8. a) Temperature evolution of the IR spectra of the PSC in the νas(H2O), νs(H2O) and ν(NH) vibrations region (3680−3360 cm-1), b) the wavenumber positions dependence of the bands at temperatures between 12 and 295 K.
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A
N
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Figure 9. a) Temperature evolution of the IR spectra of PSB in the ν(NH) vibrations region (3200−3050 cm-1), b) the wavenumber positions of the bands in the spectra at temperatures between 13 and 296 K.
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Figure 10. a) Temperature evolution of the IR spectra of PSC in the ν(NH) vibrations region (3200−3050 cm-1), b) the wavenumber positions of the bands at temperatures between 12 and 295 K.
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Figure 11. Temperature dependence of T1 relaxation times observed for PSB and PSC. The lines were calculated by using the best-fit parameters given in Table S3.
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Table 1. Crystal data and structure refinement parameters for PSB. (C4H12N2)2[Sb2Br10]·2H2O (PSB) Formula weight [g
mol-1]
1254.94 (C4H12N2)2[Sb2Br10]•2H2O
Temperature [K]
80(2)
Wavelength [Å]
0.71073
Crystal system
Monoclinic
Space group
P21/n
a [Å]
9.818(2)
b [Å]
14.357(2)
c [Å]
10.315(2)
ß [°]
99.89(3)
V [Å3]
1432(2) 2
Dcalc [Mg
m-3]
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Z
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Chemical formula
2.910 15.847
F(000)
1144
Crystal size [mm3]
0.14 x 0.13 x 0.09
θ range [°]
2.8-25.5
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A
N
μ [mm-1]
Ranges of h, k, l
−11≤ h ≤ 7 −17 ≤ k ≤ 15
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−12 ≤ l ≤ 12
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Absorption correction
Analytical
Tmin/Tmax
0.244/0.392
No. of measured,
6775/2666/2392
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independent and observed [I > 2σ(I)] reflections
0.023
Refinement method
Full-matrix least-squares on F2
Goodness-of-fit on F2
1.07
Final R indices [I > 2σ(I)]
R1 = 0.021
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Rint
R indices (all data)
wR2 = 0.044 R1 = 0.025 wR2 = 0.045
∆ρmax/∆ρmin [e A-3]
0.58/-0.69
H-atom treatment
H atoms treated by a constrained refinement
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Table 2. Selected bond lengths [Å] and angles [°] for the PSB crystal at 80 K. 2.870(4)
Br1−Sb1−Br3
87.43(4)
Sb1−Br2
2.711(2)
Br1−Sb1−Br3i
88.55(2)
Sb1−Br3
3.066(3)
Br2−Sb1−Br1
176.54(4)
Sb1−Br3i
3.256(4)
Br2−Sb1−Br3
90.22(3)
2.574(2)
Br2−Sb1−Br3i
2.629(3)
Br3−Sb1−Br3i
Sb1−Br4 Sb1−Br5
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Sb1−Br1
94.11(5) 93.20(2)
Br4−Sb1−Br1
86.26(2)
Br4−Sb1−Br2
91.10(2)
Br4−Sb1−Br3
87.14(5)
Br4−Sb1−Br3i
174.77(4)
Br5−Sb1−Br1 Br5−Sb1−Br2
91.73(2) 178.01(2)
Br5−Sb1−Br3i
87.05(3) 86.80(2)
Sb1−Br3−Sb1i
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Symmetry code: i -x+1, -y+1, -z+1.
90.61(4)
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N
Br5−Sb1−Br3
92.43(3)
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Br4−Sb1−Br5
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Table 3. The geometry parameters ([Å] and [°]) of the selected hydrogen bonds in the crystal of PSB at 80 K. D−H···A
D−H
H···A
D···A
<(DHA)
0.90
2.76
3.421(3)
131
N1−H11···Br4ii
0.90
2.96
3.719(3)
143
N1−H12···Br3iii
0.90
2.59
3.440(3)
157
N2−H13···Br3i
0.90
2.51
3.356(4)
156
N2−H14···O1W
0.90
2.13
2.910(4)
144
O1W−H1W···Br1
0.85
2.78
3.522(3)
147
0.85
2.63
3.428(3)
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N1−H11···Br1ii
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O1W−H2W···Br5iv
i
ii
Symmetry codes: -x+1, -y+1, -z+1; x-1/2, -y+1/2, z+1/2;
iii
-x+3/2, y-1/2, -z+3/2;
158 iv
x+1/2, -y+1/2, z+1/2.
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S0025-5408(17)33154-9 https://doi.org/10.1016/j.materresbull.2018.03.048 MRB 9929
To appear in:
MRB
Received date: Revised date: Accepted date:
14-8-2017 9-3-2018 26-3-2018
Please cite this article as: Moskwa M, Bator G, Piecha-Bisiorek A, Jakubas R, Medycki W, Ci˙zman A, Baran J, X-ray structure and investigation of molecular motions by dielectric, vibrational and 1 H NMR methods for two organic-inorganic hybrid piperazinium compounds: (C4 H12 N2 )2 [Sb2 Cl10 ]·2H2 O Materials Research Bulletin (2010), and (C4 H12 N2 )2 [Sb2 Br10 ]·2H2 O, https://doi.org/10.1016/j.materresbull.2018.03.048 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
X-ray structure and investigation of molecular motions by dielectric, vibrational and 1H NMR methods for two organic-inorganic hybrid
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piperazinium compounds: (C4H12N2)2[Sb2Cl10]·2H2O and (C4H12N2)2[Sb2Br10]·2H2O
Marcin Moskwaa, Grażyna Batora, Anna Piecha-Bisioreka*, Ryszard Jakubasa, Wojciech Medyckib, Agnieszka Ciżmanc and Jan Barand
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wrocław, Poland.
b
Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland.
Division of Experimental Physics, Wroclaw University Science and Technology, Wybrzeże Wyspiańskiego 27, 50-
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c
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a
d
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370 Wrocław, Poland.
Institute of Low Temperatures and Structural Research, Polish Academy of Sciences, Okólna 2, 50-422, Wrocław,
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*Corresponding Author
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Poland.
E-mail address: [email protected] (Anna Piecha-Bisiorek)
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Graphical abstract
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Highlights Bis(piperazine-1,4-diium) decabromodiantimonate(III) (PSB) dihydrate has been synthesized and characterized;
The structural phase transition for PSB at ca. 50 K has been confirmed by the dielectric and 1H NMR spectroscopy results.
The molecular dynamic motion parameters of the organic cations and water molecules have been evaluated and compared for PSB and PSC
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ABSTRACT
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Bis(piperazine-1,4-diium) decabromodiantimonate(III) dihydrate, (C4H12N2)2[Sb2Br10]·2H2O, (abbreviated as PSB) has been synthesized and characterized by single-crystal X-ray diffraction studies. The obtained results indicate that PSB is isostructural with a recently described chloride analogue, (C4H12N2)2[Sb2Cl10]2H2O (PSC), crystallizing with R2MX5·nH2O stoichiometry and characterized by the discrete zero-dimensional anionic species. The crystal structure of PSB is described by monoclinic symmetry in a P21/n space group. Dielectric measurements (down to 25 K) and IR spectral analyses (measured over a broad temperature range) suggested a much more complicated phase situation below 80 K than for that of PSC. To verify and compare the molecular motions of the organic cations in both analogues, a proton magnetic resonance (1H NMR) technique was also applied.
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1. Introduction
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KEYWORDS: piperazine-1,4-diium; phase transition; dielectric; 1H NMR; IR.
The conscious synthesis and design of organic-inorganic hybrid materials based on divalent or
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trivalent metal halides has attracted scientific attention due not only to the interesting structural topologies of these compounds but also to their unique chemical and physical properties as well
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as possible novel applications in optoelectronics, data communication, switchable dielectric devices and rewritable optical data storage [1-3].
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The family of organic haloantimonate(III)/halobismuthate(III) hybrids, defined by the general
formula RaMbX(3b+a) (where X = Cl, Br or I; M = Sb(III) or Bi(III); and R is an organic cation), have a tendency to constitute discrete (mono-) or polyoctahedral anions in the crystalline state, where the basic MX6 octahedral units are connected either by corners, edges or by faces. These systems usually form zero- (0D), one- (1D), two- (2D) or sparsely three-dimensional (3D) inorganic networks [4, 5]. It is interesting that the ferroelectric properties in this group of
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compounds have been limited only to few chemical stoichiometries, namely, R5M2X11 [6-10], R3M2X9 [11-13], RMX4 [14,15] and R2MX5 [16-19]. The anionic framework of R5M2X11 compounds is characterized by the presence of the discrete (0D) dioctahedral units [M2X11]5-, whereas the nonlinear electric properties among R3M2X9 compounds were reported only for the compounds with 2D anionic layers. Regarding the remaining two compound types (RMX4 and
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R2MX5), ferroelectric properties were observed for the crystals built up of the 1D anionic
substructure with cis or trans geometry of the [MX5]2- chains. It is worth noting that paraelectricferroelectric phase transitions (PTs), found in the R5M2X11, R3M2X9, RMX4 and in the majority of R2MX5 stoichiometries (e.g., (MV)[BiBr5] [17] (where MV is the methyl viologen dication), (C3N2H5)2[SbCl5] [18] or (C2H5NH3)2[BiCl5] [19] appear due to a distortion of the trans- or cisconnected octahedra leading to the strong polar polyanionic substructures (“displacive”
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contribution).
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Very recently, Sghaier et al. [20] have reported the first example of an organic-inorganic piperazine-1,4-diium hybrid: (C4H12N2)2[Sb2Cl10]2H2O (abbreviated PSC) which crystallized as
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R2MX5 and was characterized by discrete 0D anionic sublayers. For crystals of PSC, the was not observed for this compound.
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ferroelectricity was postulated to appear below 70 K. The ferroelectric hysteresis loop, however,
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In this paper, we report the synthesis, crystal structure, dielectric and vibrational studies of
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bis(piperazine-1,4-diium) decabromodiantimonate(III) dihydrate, (C4H12N2)2[Sb2Br10]·2H2O (PSB) in addition to the vibrational properties of PSC. The molecular motions of the organic cations are studied by means of proton magnetic resonance (1H NMR) for both piperazinium
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analogues. The molecular mechanism of the structural PTs in PSB and PSC is also proposed.
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2. EXPERIMENTAL DETAILS Synthesis of the complexes
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Starting materials for the synthesis of piperazinium-1,4-diium haloantimonates(III), PSB and
PSC, were obtained from commercial sources: (Sigma-Aldrich) Sb2O3 (99.99%), C4H10N2·6H2O (98%), HBr (48%), HCl (37%) and SbBr3 (99.9%) (ABCR). An aqueous solution of piperazine was added to solutions of Sb2O3 or SbBr3 dissolved in concentrated HCl or HBr. After few days, the polycrystalline materials were formed by slow evaporation from solution. The polycrystalline solids were recrystallized and characterized by
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elemental analysis: PSB: C: 7.88%, N: 4.64%, and H: 2.17% (calc. C: 7.66%, N: 4.47%, and H: 2.25%); PSC: C: 12.03%, N: 6.95%, and H: 3.51% (calc. C: 11.86%, N: 6.91%, and H: 3.48%). The purity of the PSB was verified by XRD (see Figure S1-Supplementary Materials). Thermal analysis Simultaneous thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were
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carried out on a Setaram SETSYS 16/18 instrument from 300-900 K with a ramp rate of 5 K·min-1 under nitrogen (flow rate: 1 dm3·h-1). X-ray diffraction analysis
Single-crystal X-ray diffraction data for PSB were collected at 80 K on an Agilent
Technologies Xcalibur, Ruby к-axis four-circle diffractometer equipped with an Oxford
Cryosystem cooler using graphite monochromated MoKαradiation. The structure was solved by
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direct methods with the SHELXS-2014/7 [21] program and refined by the full-matrix least-
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squares methods on all F2 data using SHELXL-2014/7 [22]. Data collection was performed by using CrysAlis CCD; reduction was executed on CrysAlis Pro [23]. All non-hydrogen atoms
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were refined anisotropically. H atoms attached to O and N atoms were found in a difference
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Fourier map. Water H atoms and N-bound H atoms were refined with O─H, H···H, N─H, H···H distances restrained to 0.850(2), 1.380(2), 0.900(2), 1.450(2) Å, respectively. H atom isotropic
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temperature factors were assumed as 1.2 times Ueq(N) and 1.5 times Ueq(O). Water H and N-
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bound H atoms were then constrained to ride on their parent atoms (AFIX 3 instruction in SHELXL-2014/7) [22]. C-bound H atoms were set as a riding model, and their isotropic temperature factors were assumed to be 1.2 times Ueq. The crystal data together with
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experimental and refinement details are given in Table 1. Crystallographic data for the structure reported in this paper (excluding structures factors) have been deposited with the CCDC No.
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1564229.
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Dielectric measurements Two different methods were applied for the dielectric measurements of PSB. The complex
value of dielectric permittivity, ε* = ε’ - iε’’ was first measured using an Agilent E4980A Precision LCR Meter in the frequency range between 135 Hz and 2 MHz and in the temperature range between 85–310 K. The other type of measurement was obtained using an Alpha-A High Resolution Dielectric Modular Measurements System (Novocontrol) assisted by a LakeShore
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temperature controller. The dielectric measurements were performed as a function of frequency from 10 Hz and to 10 MHz. The temperature of the sample between 25 K and 100 K was maintained by a jet of pure helium; the temperature control was better than 0.5 K. In both experiments, the polycrystalline material was used in the form of pressed pellets. The diameter of the pellets was 10 mm, and the thickness was 1 mm. The overall error in the estimation of the
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real part of dielectric permittivity value was less than 5%. The silver electrodes were painted on both opposing faces of the pellets. Infrared studies
The infrared spectra of PSB and PSC (suspension in Nujol between CsI windows) were
measured with a Bruker IFS-88 spectrometer from 4000-400 cm-1 in a wide temperature range (12–296 K) with a resolution of 2 cm-1 (see Figure S2a and b). An APD Cryogenics Displex
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Closed Cycle Refrigeration System, model CSW-202, was used for the temperature dependent
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studies. The temperature of the sample was maintained with an accuracy of 0.1 K by a Scientific Instruments INC controller Series 5500. The Grams Galactic Industries program was used for a
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numerical fitting of the experimental data. The Gaussian functions were used for fitting the shape
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of the infrared bands. Powder FT-Raman were recorded on an FRA-106 attached to a Bruker IFS-88 using a Nd:YAG diode pump laser. The measurements were performed at room
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temperature over a wavenumber range of 3500-80 cm-1 with resolution better than 2 cm-1. Table
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S1 summarizes the observed positions of the bands in the IR and Raman spectra along with their assignments. The assignments of the internal modes of the organic cation for compounds containing piperazine were used as guides [24-28]. The observed Raman and IR bands between
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400 and 50 cm-1 are tentatively assigned to the internal modes of the [Sb2Br10]4- and [Sb2Cl10]4anions on the basis of comparison with other studies carried out on numerous
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haloantimonates(III) [29].
Proton magnetic resonance (1H NMR)
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NMR measurements were made using an ELLAB TEL-Atomic PS 15 (operating at 25 MHz at
temperatures from room temperature down to 77 K) and a Tecmag Scout (operating at 24.8 MHz at temperatures below liquid nitrogen) spectrometers. The spin-lattice relaxation times, T1, were measured using a saturation sequence of π /2 pulses followed by a variable time interval, τ, and a reading π /2 pulse. The magnetization recovered exponentially within experimental error at all temperatures. The temperature of the sample was adjusted by liquid nitrogen cooling and was
5
controlled by a UNIPAN 660 temperature controller operating with a Pt 100 sensor, providing extended temperature stability better than 1 K. Below temperatures of liquid nitrogen a helium cooled Leybold cryostat was applied. The powdered sample of PSB/PSC was evacuated at room temperature and then sealed under vacuum in a glass ampoule. All measurements were made upon heating the sample. The errors in the measurements of T1 were estimated to be
SC RI PT
approximately 5%. 3. Results and discussion 3.1 Thermal analysis
Thermal stability of PSB was studied by means of TGA and DTA. The result for PSB shows
that the compound is stable up to ca. 360 K (Figure S3). On the DTA curve, a small, broad peak
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corresponding to an endothermal effect between 360 and 460 K was assigned to the loss of two
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water molecules per formula unit of the crystal. It should be noted that the mass loss on the order
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of ca. 3% is probably related to the complete dehydration process (2.87% of water in the title compound). Further heating showed two endothermic peaks on the DTA curve at ca. 530 and
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580 K. Heating above ca. 600 K leads to sample decomposition.
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3.2 X-ray
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PSB crystallizes in the monoclinic system in P21/n (No. 14) space group and is isomorphous with a PSC analogue reported previously [20]. In the asymmetric part of the unit cell, there is
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one piperazinium-1,4-diium dication, half of a discrete decabromodiantimonate(III) anion and one water molecule. The view of the independent part and numbering scheme for PSB are presented in Figure 1.
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In the PSB crystal, the SbBr6 octahedra are combined in pairs by two bridging Br atoms giving
rise to centrosymmetric binuclear [Sb2Br10]4- anions with a Sb(1)−Br(3)−Sb(1)i angle of
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86.80(2)°. Sb−Br distances fall into two ranges: from ~2.6–2.9 Å for the terminal Br atoms and from ~3.1–3.3 Å for the bridging ones (Table 2). The longest terminal distance of 2.870(4) Å for Sb(1)−Br(1) was due to the presence of two hydrogen bonds between Br and H atoms; the latter atom belonging to either the N atoms of the organic groups or the O atoms of water molecules. The bridging Sb(1)−Br(3) and Sb(1)−Br(3)i bonds (3.066(3) Å and 3.256(4) Å, respectively) lie opposite to the trans Sb−Br terminal bonds (Sb(1)−Br(4), 2.574(2) Å; Sb(1)−Br(5), 2.629(3) Å).
6
The trans Sb−Br terminal bonds are shorter than the remaining Sb−Br bonds (2.711(2) Å for Sb(1)−Br(2) and 2.870(4) Å in the case of Sb(1)−Br(1)). The bonds and angles within the [Sb2Br10]4- anion are listed in Table 2. The characteristic feature of the PSB crystal was the presence of the infinite, two-dimensional hydrogen bond system perpendicular to the ac-axis resulting from the interaction between the [Sb2Br10]4- anions and water molecules (see Figure 2).
SC RI PT
As shown in Figure 3a, the cations are stacked in the substructure channels created by
binuclear [Sb2Br10]4- anions along the [-10-1] direction. The organic groups, present as dications, have a chair conformation. The same conformation of the dication moieties was observed in the PSC structure [20]. Water molecules are the proton acceptors in the moderately strong N−H···O type hydrogen bonds (Table 3) as illustrated in Figure 3b.
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3.3 Dielectric measurements
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Recently, reported dielectric studies on PSC revealed relaxation processes in the kilohertz frequency region when approaching the PT temperature (Tc=70 K) [20]. This was a motivation to
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carry out the dielectric measurements for PSB in wide frequency and temperature ranges as well.
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The main purpose of this study was to check if the enormous increase of ’, similar as for PSC, could be observed for PSB.
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Temperature dependencies of the complex electric permittivity of PSB measured at selected
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frequencies are shown in Figure 4. Two relaxation processes were detected from 80–310 K and between 85–175 K for relaxators 1 and 2, respectively. The dielectric increment, o for the latter process is small ( was below 0.2), while the former is characterised by a larger
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increment = 3.
High temperature dielectric relaxation processes are well-described by the Cole-Cole equation
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with a single relaxation time:
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* 'i ' ' 1
0 1 , 1 1 i 1
(1)
where o and are the low and high frequency limits of electric permittivity, respectively;
corresponds to the angular frequency, is the macroscopic relaxation time and is the distribution of the relaxation time parameter.
7
The Cole-Cole diagrams at four selected temperatures for relaxator 1 are depicted in Figure 5. The estimated value of the parameter is 0.2. The activation energy, EA,diel1, can be estimated directly from the Arrhenius equation for the dielectric relaxation time:
E A , diel1 , RT
1 01 exp
(2)
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where o1 is the high temperature limit of the relaxation time, R – gas constant 8.314 J/mol·K and T – absolute temperature.
The EA,diel1 value for relaxator 1 of PSB was approximately 353 kJ/mol (Figure S4). Activation energy values such as that are typical for dielectric processes found in other
haloantimonate(III) and halobismuthate(III) crystals containing bulky organic cations[30-33]. The activation energy for relaxator 2 was 312 kJ/mol. The macroscopic relaxation time for
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relaxator 2 was estimated from the maxima of the imaginary parts, ’’, of the electric permittivity
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(Figure 4b). It should be noted that the values, estimated from the Cole-Cole equation for
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relaxator 1, are on the order of 19-21, which are still relatively high. This may indicate an
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additional high frequency dielectric relaxation process over this temperature range. Taking into account the results reported by Sghaier et al. [20], we measured the complex
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dielectric permittivity below 80 K using an Alpha-A High Resolution Dielectric Modular Measurements System (Novocontrol) with a pellet placed in the cell under high vacuum. The
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dielectric response function strongly depends on the quality of the polycrystalline sample and measurement conditions. Samples kept in the measurement cell under vacuum lose water
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molecules. That means such a sample should be treated as a defective material. Measurements were carried out under different experimental conditions. The samples, which were previously
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measured under vacuum, showed an essentially different response than those measured under ambient pressure with a nitrogen atmosphere. It proved that the observed difference in the dielectric response, between the samples measured under vacuum and ambient pressure, may be
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explained in terms of water molecule loss. As seen in Figure 6a, ’ increases continuously over the analysed temperature region and exhibits weak anomalies at ca. 80, 50 and 30 K. It is interesting that between 100 and 25 K, another relaxation process was observed (Figure 6b) with a dielectric increment, , of ca. 0.6. It should be noted that in order to confirm the polar character of the lowest temperature phase of
8
PSB (below 50 K) the measurements of the pyroelectric current should be carried out. Such behaviour is characteristic of quantum ferroelectrics, e.g., SrTiO3 [34]. We concluded that this may be treated as a potential quantum ferroelectric, since we cannot exclude the ferroelectric properties of PSB.
SC RI PT
3.3 Spectroscopic studies
To confirm the presence of PT in PSB as well as to analyse the role of the piperazine-1,4-
diium dication and water molecules in the molecular mechanism of the low-temperature PTs in both compounds, IR spectra at various temperatures were measured (see Figures S2a and S2b). It should be emphasized that the changes in positions, in intensities as well as of FWHM (full
width at half maximum) found for PSC and PSB are very subtle and may indicate the continuous
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nature of the structural anomalies. It is noteworthy that the changes in the positions of selected
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bands for PSC are smaller than those of PSB. This is most likely due to the strong Christiansen effect [35, 36].
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The most pronounced anomalies are visible from 3680 and 3370 cm-1, where bands arising from
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the ν(OH) and ν(NH) vibrations (Figures 7a and 8a) appear. For PSB, four well-separated components can be distinguished at low temperature, which shift continuously towards higher
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wavenumbers during the heating cycle. Around the PT point (50 K), an insignificant change in
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the positions of all bands analysed was observed (see Figure 7b); two of them (denoted as 2 and 3) subsequently disappear at 125 and 250 K, respectively. The PSC results were very similar (Figure 8b); four well-shaped bands are visible and undergo a weak anomaly related to the
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structural PT at 70 K. One of the bands (No. 4) vanished at approximately 225 K while the shoulder, depicted as 2, appeared a few degrees below and vanished a few degrees above Tc. It
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should be stressed, however, that during heating of both PSB and PSC samples, a significant decrease in the intensities of all analysed bands was observed.
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The temperature evolutions of the PSB and PSC bands observed between 3200 and 3050 cm-1
and assigned to the νas(NH) and νs(NH) vibrations are presented in Figures 9 and 10, respectively. The detailed analyses of this frequency region, especially for the bromide (PSB) analogue, was very difficult to observe due to the Christiansen effect mentioned above. For PSB, we observed at least four bands at the lowest temperature, the bandwidths of which were the smallest and increased significantly upon heating the sample. The positions of these bands are almost
9
temperature independent; nevertheless, some signatures of PT at 50 K are visible (Figure 9b). For the PSC compound, the IR spectra at low temperatures are much more complicated and featured by eight bands, four of which create characteristic shoulders which disappeared at different temperatures (Figure 10b). The PT at 70 K is clearly visible mainly as a change in the slope of the = f(T) curves.
SC RI PT
The observed changes in the IR spectra may indicate the participation of the organic dications in the mechanisms of the PT found for both PSC and PSB crystals; however, their contribution is weakly reflected.
3.5 Proton magnetic resonance (1H NMR)
The temperature dependencies of the proton nuclear spin-lattice relaxation time, T1, for the
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PSC and PSB compounds are shown in Figure 11. We distinguished four different temperature
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ranges for T1 runs observed for both compounds. In the lowest temperature range (T 40 K) the
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spin-lattice relaxation times, T1, remained constant. The next temperature range, between 40 K and ca. 110 K, a double minimum was observed for both compounds. Then, up to 240 K, the T1
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value increased and reached maximum values at 221 K and 243 K for PSB and PSC, respectively. The fourth temperature range, above 240 K, the observed T1 value for both
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compounds strongly decreased and reached the minimum for one of them (PSB T1min=37 ms at
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420 K). It should be noted that between 157 and 290 K, we observed two components of T1, long
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and short.
Furthermore, the T1 vs. 1/T curve for PSB reveals a rapid anomaly at ca. 50 K, which confirmed the structural PT suggested from dielectric measurements. A similar anomaly on the
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T1(1/T) curve was observed for PSC near 65 K and was in a good agreement with the dielectric studies reported in [20].
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When analysing the possible mechanisms of proton relaxation in the compounds under
investigation, we may consider the following types of molecular interactions and motions as the temperature increases: - interactions of protons, from either cations or water molecules, with the neighbouring quadrupolar halogens, Cl and Br, – jumps of protons in hydrogen bonds,
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– motions of water molecules (180° flip), – reorientations of the piperazine cations (libration, 180° flip), – reorientations of the piperazine cations around the pseudo six-fold symmetry axes (C6’). At the lowest temperatures, analogous to previously studied compounds containing halogen atoms, the first possibility has to be taken into account, i.e., a domination of the quadrupole
SC RI PT
interactions [37-39]. In the next temperature region (above 40 K), the observed double minimum may be a result of the active proton jumps within the hydrogen bonds of both compounds. One possible hydrogen bond is formed between a proton of the cation (primarily from the nitrogen) and a halogen atom (Cl or Br). The other hydrogen bond may appear between a proton from a
water molecule and a halogen in the anionic species. The T1 temperature dependencies may be fitted using the BPP theory equation [40]:
(3)
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N
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C1 C2 4 C1 4 C 2 1 C2 , C1 2 2 2 2 2 2 2 2 T1 1 0 C1 1 40 C1 1 0 C 2 1 40 C 2
where C1 and C2 are relaxation constants, c1 and c2 are the correlation times assigned to the
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protons jumps of the two different types of hydrogen bonds. The temperature dependence of the correlation times in this temperature region is well described by the Arrhenius law
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ci=oiexp(Ea/RT).
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The two next temperature regions, above and below 240 K, are assigned to the gradual release of the piperazinium cation motions (long time component), whereas we ascribe the short
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component of T1 to the relaxation processes caused by the reorientation of the water molecules [20]. The parameters of the fitting procedure applied to the corresponding minima and slopes of the experimental T1 temperature dependencies for PSC and PSB are collected in Table S3. It
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should be noted that the relatively large activation energy above ca. 300 K for both compounds (35 kJ/mol – PSB, 21 kJ/mol – PSC) is characteristic either of the overall or the C6’–type
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reorientation motions of these bulky cations. 4. Conclusion PSB crystallizes in the monoclinic system with P21/n space group and is isomorphic with the previously reported PSC analogue [20]. The crystal structure of PSB (at 80 K) contains one ordered piperazinium-1,4-diium dication, half of a discrete decabromodiantimonate(III) anion
11
and a water molecule. In spite of their structural similarities, the dielectric properties of the two crystals in this study were significantly different, especially below 100 K. The dielectric response for PSC resembled that encountered in the ferroelectric crystals, whereas the dielectric anomaly of PSB was quite weak and typical of a non-ferroelectric PT. However, it does not exclude the presence of polar phase at the lowest temperatures. For the latter analogue, we
SC RI PT
address structural PT at ca. 50 K, which was confirmed by dielectric and 1H NMR spectroscopy results. The vibrational (IR) studies on PSB and PSC showed that the low temperature PTs were weakly reflected in the temperature dependent infrared spectra, which indicated that the
dynamics of the organic cations is not crucial in the PT mechanism. The visible anomalies on the T1 vs. 1/T curves at approximately 70 K for PSC and 50 K for PSB indicated that proton motions may play an important role within the various types of hydrogen bonds.
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The measurements of the spin-lattice relaxation times for PSB and PSC over a wide
N
temperature region (10 – 430 K) allowed us to propose the following molecular motions in different temperature ranges:
In the temperature range below 40 K, the quadrupole interactions dominate;
Between 40 and 110 K, the double minima of T1 are assigned to the proton jumps along
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the hydrogen bonds, which are expected to contribute to the phase transition Above 110 K, the piperazinium cation reorients in a successive way (from libration to
TE
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mechanism of both analogues; overall reorientation);
From 160–290 K, the water molecules relax independently.
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ACKNOWLEDGEMENT This work has been supported by the Polish Ministry of Science and Higher Education Agreement Nr 3580/ZIBJ DUBNA/2016/0 and partially by the International Program ZIBJ
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Dubna №04-4-1121-2015/2017.
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References [1]
J. F. Scott, Applications of modern ferroelectrics., Science. 315 (2007) 954–959. DOI:10.1126/science.1129564.
[2]
S.T. Han, Y. Zhou, V.A. Roy, Towards the development of flexible non-volatile memories, Adv. Mater. 25 (2013) 5425–5449. DOI:10.1002/adma.201301361. J. Li, J. Claude, L.E. Norena-Franco, S.I. Seok, Q. Wang, Electrical energy storage in
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[3]
ferroelectric polymer nanocomposites containing surface-functionalized BaTiO3 nanoparticles, Chem. Mater. 20 (2008) 6304–6306. DOI:10.1021/cm8021648. [4]
L. Sobczyk, R. Jakubas, J. Zaleski, Self-assembly of Sb(III) and Bi(III) halo-coordinated octahedra in salts of organic cations. Structure, properties and phase transitions., Pol. J. Chem. 71 (1997) 265–300.
W. Zhang, R.-G. Xiong, Ferroelectric metal-organic frameworks, Chem. Rev. 112 (2012)
U
[5]
J. Lefebvre, P. Carpentier, R. Jakubas, L. Sobczyk, The para-ferroelectric phase transition
A
[6]
N
1163–1195. DOI:10.1021/cr200174w.
in (NH3CH3)5Bi2Cl11 (P.M.A.C.B.), Phase Transitions. 33 (1991) 31–41. [7]
M
DOI:10.1080/01411599108207709.
R. Jakubas, A. Piecha, A. Pietraszko, G. Bator, Structure and ferroelectric properties of
D
(C3N2H5)5Bi2Cl11, Phys. Rev. B. 72 (2005) 104107-1–8. [8]
TE
DOI:10.1103/PhysRevB.72.104107. A. Piecha, A. Pietraszko, G. Bator, R. Jakubas, Structural characterization and ferroelectric ordering in (C3N2H5)5Sb2Br11, J. Solid State Chem. 181 (2008) 1155–1166. [9]
EP
DOI:10.1016/j.jssc.2008.02.029. A. Piecha, A. Białońska, R. Jakubas, Structure and ferroelectric properties of
CC
[C3N2H5]5[Bi2Br11], J. Phys. Condens. Matter. 20 (2008) 325224-1–9. DOI:10.1088/09538984/20/32/325224.
A
[10] [11]
J. Jóźków, R. Jakubas, G. Bator, A. Pietraszko, Ferroelectric properties of (C5H5NH)5Bi2Br11, J. Chem. Phys. 114 (2001) 7239–7246. DOI:10.1063/1.1349897. R. Jakubas, G. Bator, L. Sobczyk, J. Mróz, Dielectric and pyroelectric properties of (CH3NH3)3Me2Br9 (Me = Sb, Bi) crystals in the ferroelectric phase transition regions, Ferroelectrics. 158 (1994) 43–48. DOI:10.1080/00150199408215991.
[12]
G. Bator, R. Jakubas, L. Sobczyk, J. Mróz, Dielectric and pyroelectric properties of
13
[N(CH3)3H]3Sb2Cl9 in the low temperature region, Ferroelectrics 141 (1993) 177-187. DOI:10.1080/00150199308223445. [13]
M. Gdaniec, Z. Kosturkiewicz, R. Jakubas, L. Sobczyk, Structure and mechanism of ferroelectric phase transition in tris(dimethylammonium)-nonachlorodiantimonate(III), Ferroelectrics. 77 (1988) 31–37. DOI:10.1080/00150198808223224. R. Jakubas, Z. Ciunik, G. Bator, Ferroelectric Properties of [4-NH2C5H4NH][SbCl4]. Phys.
SC RI PT
[14]
Rev. B67 (2003) 024103-1–6. DOI:10.1103/PhysRevB.67.024103. [15]
G. Xu, Y. Li, W.-W. Zhou, G.-J. Wang, X.-F. Long, L.-Z. Cai, M.-S. Wang, G.-C. Guo, J.-S. Huang, G. Bator, R. Jakubas, A ferroelectric inorganic-organic hybrid based on NLO-phore stilbazolium, J. Mater. Chem. 19 (2009) 2179–2183. DOI:10.1039/B819473D.
M. Owczarek, P. Szklarz, R. Jakubas, A. Miniewicz, [NH2(C2H4)2O]MX5: a new family of
U
[16]
N
morpholinium nonlinear optical materials among halogenoantimonate(III) and halogenobismuthate(III) compounds. Structural characterization, dielectric and W. Bi, N. Leblanc, N. Mercier, P. Auban-Senzier, C. Pasquier, Thermally induced Bi(III)
M
[17]
A
piezoelectric properties., Dalton Trans. 41 (2012) 7285–7294. DOI:10.1039/c2dt30291h. lone pair stereoactivity: Ferroelectric phase transition and semiconducting properties of
D
(MV)BiBr5 (MV = methylviologen), Chem. Mater. 21 (2009) 4099–4101. [18]
TE
DOI:10.1021/cm9016003.
A. Piecha-Bisiorek, A. Białońska, R. Jakubas, Novel organic–inorganic hybrid ferroelectric: bis(imidazolium) pentachloroantimonate(II), (C3N2H5)2SbCl5, J. Mater.
[19]
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Chem. 22 (2012) 333–336. DOI:10.1039/c1jm13597j. A. Piecha-Bisiorek, A. Gągor, R. Jakubas, A. Ciżman, R. Janicki, W. Medycki,
CC
Ferroelectricity in bis(ethylammonium) pentachlorobismuthate(III): synthesis, structure, polar and spectroscopic properties, Inorg. Chem. Front. 4 (2017) 1281–1286.
A
DOI:10.1039/C7QI00254H.
[20]
M.O.M. Sghaier, K. Holderna-Natkaniec, A. Wozniak-Braszak, P. Czarnecki, S. Chaabouni, Structure and internal dynamics of bis(piperazine-1,4-diium) pentachloroantimonate(III) monohydrate, Polyhedron. 79 (2014) 37–42. DOI:10.1016/j.poly.2014.04.030.
[21] G.M. Sheldrick, A short history of SHELX, Acta Crystallogr. Sect. A Found. Crystallogr.
14
64 (2007) 112–122. DOI:10.1107/S0108767307043930. [22] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem. 71 (2015) 3–8. DOI:10.1107/S2053229614024218. [23] CrysAlis CCD, CrysAlis Pro, Agilent Technologies, Version 1.171.37.31. [24] P. Hendra, D. Powell, The infra-red and Raman spectra of piperazine, Spectrochim. Acta.
SC RI PT
4408 (1962) 299–306. DOI:10.1016/S0371-1951(62)80138-6.
[25] S. Gunasekaran, B. Anita, Spectral investigation and normal coordinate analysis of piperazine, Indian J. Pure Appl. Phys. 46 (2008) 833–838.
[26] R.J. Obremski, C.W. Brown, E.R. Lippincott, Vibrational spectra of single crystals. polymorphic solids of cyclohexane, J. Chem. Phys. 49 (1968) 185–191. DOI:10.1063/1.1669807.
U
[27] H. Takahashi, T. Shimanouchi, K. Fukushima, T. Miyazawa, Infrared spectrum and
N
normal vibrations of cyclohexane, J. Mol. Spectrosc. 13 (1964) 43–56. DOI:10.1016/0022-2852(64)90053-0.
A
[28] R.G. Synder, J.H. Schachtschneider, A valence force field for saturated hydrocarbons,
M
Spectrochim. Acta. 21 (1965) 169–195. DOI:10.1016/0371-1951(65)80115-1. [29] H.L. Sheu, J. Laane, Trans effect in halobismuthates and haloantimonates revisited.
D
molecular structures and vibrations from theoretical calculations, Inorg. Chem. 52 (2013)
TE
4244–4249. DOI:10.1021/ic302082a. [30] I. Płowaś, P. Szklarz, R. Jakubas, G. Bator, Structural, thermal and dielectric studies on the novel solution grown (4-dimethylaminopyridinium) chloroantimonate(III) and
EP
chlorobismuthate(III) crystals, Mater. Res. Bull. 46 (2011) 1177–1185. DOI:10.1016/j.materresbull.2011.04.013.
CC
[31] J. Zaleski, R. Jakubas, G. Bator, J. Baran, Dielectric dispersion, dilatometric and infrared studies of tris(guanidinium) enneachlorodiantimonate(III), J. Mol. Struct. 325 (1994) 95–
A
103. DOI:10.1016/0022-2860(94)80023-5.
[32] B. Bednarska-Bolek, J. Zaleski, G. Bator, R. Jakubas, On structural phase transitions in piperidinium halogenoantimonates(III) and bismuthates(III): X-ray, calorimetric, dilatometric, dielectric and Raman studies, J. Phys. Chem. Solids. 61 (2000) 1249–1261. DOI:10.1016/S0022-3697(99)00414-X. [33] P. Szklarz, J. Zaleski, R. Jakubas, G. Bator, W. Medycki, K. Falińska, The structure,
15
phase transition and molecular dynamics of [C(NH2)3]3[Sb2Br9], J. Phys. Condens. Matter. 17 (2005) 2509–2528. DOI:10.1088/0953-8984/17/15/021. [34] S. E. Rowley, L. J. Spalek, R. P. Smith, M. P. M. Dean, M. Itoh, J. F. Scott, G. G. Lonzarich, S. S. Saxena, Ferroelectric quantum criticality, Nat. Phys. 10 (2014) 367–372. DOI:10.1038/NPHYS2924.
SC RI PT
[35] C. Christiansen, Untersuchungen über die optischen Eigenschaften von fein verteilten Körpern, Ann. Der Phys. Und Chemie. 23 (1884) 298–306.
[36] C. Christiansen, Untersuchungen über die optischen Eigenschaften von fein verteilten Körpern, Ann. Der Phys. Und Chemie. 24 (1885) 439–446.
[37] M. Węcławik, P. Szklarz, W. Medycki, R. Janicki, a. Piecha-Bisiorek, P. Zieliński, R.
Jakubas, Unprecedented transformation of [I−·I3−] to [I42−] polyiodides in the solid state:
U
structures, phase transitions and characterization of dipyrazolium iodide triiodide, Dalt.
N
Trans. 44 (2015) 18447–18458. DOI:10.1039/C5DT02265G. [38] M. Wojtaś, A. Gągor, O. Czupiński, A. Piecha-Bisiorek, D. Isakov, W. Medycki, R.
A
Jakubas, Polar and antiferroelectric behaviour of a hybrid crystal – piperazinium
M
perchlorate, CrystEngComm. 17 (2015) 3171–3180. DOI:10.1039/C5CE00161G. [39] A. Piecha-Bisiorek, R. Jakubas, W. Medycki, M. Florek-Wojciechowska, M.
D
Wojciechowski, D. Kruk, Dynamics of Ferroelectric Bis(imidazolium)
TE
Pentachloroantimonate (III) by Means of Nuclear Magnetic Resonance 1H Relaxometry and Dielectric Spectroscopy, J. Phys. Chem. A. 118 (2014) 3564–3571. DOI:10.1021/jp501331c.
EP
[40] N. Bloembergen, E.M. Purcell, R. V. Pound, Relaxation effects in nuclear magnetic
A
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resonance absorption, Phys. Rev. 73 (1948) 679–712. DOI:10.1103/PhysRev.73.679.
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Figure captions
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Figure 1. The asymmetric unit of the PSB crystal structure showing the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability. Transparent part completes the chemical formula of PSB. Symmetry code is given in Table 2.
17
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Figure 2. Projection of the crystal structure of PSB, which illustrates the geometry of the hydrogen bond system.
Figure 3. Projection of the PSB crystal structure viewed along a) [-10-1] and b) [100] direction. A polyhedral representation is used for the [Sb2Br10]4- bioctahedron. Dashed lines in part b indicate selected hydrogen bonds.
18
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Figure 4. Temperature dependence of a) the real (ε’) and b) imaginary (ε’’) parts of the complex dielectric constant (ε*) measured for the powder sample of PSB crystal upon heating.
Figure 5. Cole-Cole plots at several temperatures (relaxator 1).
19
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M
A
Figure 6. Temperature dependence of a) the real (ε’) and b) imaginary (ε’’) parts of the complex dielectric constant (ε*) measured for the powder sample of PSB upon cooling below 100 K.
Figure 7. a) Temperature evolution of the IR spectra for PSB in the νas(H2O), νs(H2O) and ν(NH) vibrations region (3680−3350 cm-1), b) the wavenumber positions of the bands at selected temperatures between 13 and 296 K.
20
SC RI PT U N
A
CC
EP
TE
D
M
A
Figure 8. a) Temperature evolution of the IR spectra of the PSC in the νas(H2O), νs(H2O) and ν(NH) vibrations region (3680−3360 cm-1), b) the wavenumber positions dependence of the bands at temperatures between 12 and 295 K.
21
M
A
N
U
SC RI PT
Figure 9. a) Temperature evolution of the IR spectra of PSB in the ν(NH) vibrations region (3200−3050 cm-1), b) the wavenumber positions of the bands in the spectra at temperatures between 13 and 296 K.
A
CC
EP
TE
D
Figure 10. a) Temperature evolution of the IR spectra of PSC in the ν(NH) vibrations region (3200−3050 cm-1), b) the wavenumber positions of the bands at temperatures between 12 and 295 K.
22
SC RI PT U N
A
CC
EP
TE
D
M
A
Figure 11. Temperature dependence of T1 relaxation times observed for PSB and PSC. The lines were calculated by using the best-fit parameters given in Table S3.
23
Table 1. Crystal data and structure refinement parameters for PSB. (C4H12N2)2[Sb2Br10]·2H2O (PSB) Formula weight [g
mol-1]
1254.94 (C4H12N2)2[Sb2Br10]•2H2O
Temperature [K]
80(2)
Wavelength [Å]
0.71073
Crystal system
Monoclinic
Space group
P21/n
a [Å]
9.818(2)
b [Å]
14.357(2)
c [Å]
10.315(2)
ß [°]
99.89(3)
V [Å3]
1432(2) 2
Dcalc [Mg
m-3]
U
Z
SC RI PT
Chemical formula
2.910 15.847
F(000)
1144
Crystal size [mm3]
0.14 x 0.13 x 0.09
θ range [°]
2.8-25.5
M
A
N
μ [mm-1]
Ranges of h, k, l
−11≤ h ≤ 7 −17 ≤ k ≤ 15
D
−12 ≤ l ≤ 12
TE
Absorption correction
Analytical
Tmin/Tmax
0.244/0.392
No. of measured,
6775/2666/2392
EP
independent and observed [I > 2σ(I)] reflections
0.023
Refinement method
Full-matrix least-squares on F2
Goodness-of-fit on F2
1.07
Final R indices [I > 2σ(I)]
R1 = 0.021
A
CC
Rint
R indices (all data)
wR2 = 0.044 R1 = 0.025 wR2 = 0.045
∆ρmax/∆ρmin [e A-3]
0.58/-0.69
H-atom treatment
H atoms treated by a constrained refinement
24
Table 2. Selected bond lengths [Å] and angles [°] for the PSB crystal at 80 K. 2.870(4)
Br1−Sb1−Br3
87.43(4)
Sb1−Br2
2.711(2)
Br1−Sb1−Br3i
88.55(2)
Sb1−Br3
3.066(3)
Br2−Sb1−Br1
176.54(4)
Sb1−Br3i
3.256(4)
Br2−Sb1−Br3
90.22(3)
2.574(2)
Br2−Sb1−Br3i
2.629(3)
Br3−Sb1−Br3i
Sb1−Br4 Sb1−Br5
SC RI PT
Sb1−Br1
94.11(5) 93.20(2)
Br4−Sb1−Br1
86.26(2)
Br4−Sb1−Br2
91.10(2)
Br4−Sb1−Br3
87.14(5)
Br4−Sb1−Br3i
174.77(4)
Br5−Sb1−Br1 Br5−Sb1−Br2
91.73(2) 178.01(2)
Br5−Sb1−Br3i
87.05(3) 86.80(2)
Sb1−Br3−Sb1i
M
Symmetry code: i -x+1, -y+1, -z+1.
90.61(4)
A
N
Br5−Sb1−Br3
92.43(3)
U
Br4−Sb1−Br5
TE
D
Table 3. The geometry parameters ([Å] and [°]) of the selected hydrogen bonds in the crystal of PSB at 80 K. D−H···A
D−H
H···A
D···A
<(DHA)
0.90
2.76
3.421(3)
131
N1−H11···Br4ii
0.90
2.96
3.719(3)
143
N1−H12···Br3iii
0.90
2.59
3.440(3)
157
N2−H13···Br3i
0.90
2.51
3.356(4)
156
N2−H14···O1W
0.90
2.13
2.910(4)
144
O1W−H1W···Br1
0.85
2.78
3.522(3)
147
0.85
2.63
3.428(3)
CC
EP
N1−H11···Br1ii
A
O1W−H2W···Br5iv
i
ii
Symmetry codes: -x+1, -y+1, -z+1; x-1/2, -y+1/2, z+1/2;
iii
-x+3/2, y-1/2, -z+3/2;
158 iv
x+1/2, -y+1/2, z+1/2.
25