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Growth and spectral analysis of piperazinium l -tartrate salt: A combined experimental and theoretical approach
Accepted Manuscript Growth and spectral analysis of piperazinium L-Tartrate salt: A combined experimental and theoretical approach R. Mathammal, N. Sudha, R. Shankar, M. Rajaboopathi, S. Janagi, B. Prabavathi PII:
S0022-2860(16)31207-8
DOI:
10.1016/j.molstruc.2016.11.045
Reference:
MOLSTR 23146
To appear in:
Journal of Molecular Structure
Received Date: 3 June 2016 Revised Date:
11 November 2016
Accepted Date: 14 November 2016
Please cite this article as: R. Mathammal, N. Sudha, R. Shankar, M. Rajaboopathi, S. Janagi, B. Prabavathi, Growth and spectral analysis of piperazinium L-Tartrate salt: A combined experimental and theoretical approach, Journal of Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.11.045. 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.
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Graphical Abstract
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Growth and Spectral Analysis of Piperazinium L-Tartrate Salt: A Combined Experimental and Theoretical Approach R. Mathammala*, N. Sudhaa, R. Shankarb, M. Rajaboopathic,d, S. Janagia, B. Prabavathia a
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Department of Physics, Sri Sarada College for Women (Autonomous), Salem-636016, Tamilnadu, India
b
Department of Physics, Bharathiar University, Coimbatore-641046, Tamilnadu, India
Department of Physics, Periyar University, Salem-636011, Tamilnadu, India
d
State Key Laboratory of Crystal Materials,Shandong University,Jinan-250100,China
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Abstract
This report discusses crystal structure, molecular arrangements, vibrational analysis, UV-Vis-NIR spectrum, fluorescence emission and second harmonic generation (SHG) efficiency of piperazinium L-tartrate (PPZ2+·Tart2-) crystals with the support of theoretical analysis. A good optical quality PPZ2+·Tart2- crystals were grown from slow evaporation of aqueous
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solution. The PPZ2+·Tart2- crystal belongs to monoclinic system with non-centrosymmetric space group P21. The charge transfer from donor to acceptor moieties and corresponding changes in the bond lengths and bond angles have been observed. The observed functional group vibrations in the experimental FTIR and the Raman spectrum were assigned and compared with theoretical
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wavenumbers of PPZ2+·Tart2-.The electron distribution on the donor and acceptor in PPZ2+·Tart2has been clearly visualised using molecular electrostatic potential map. Compared with L-tartaric acid, red shift was observed in absorption and fluorescence spectrum. The low value of dielectric
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constant and dielectric loss at the higher frequency and its high second harmonic efficiency suggest PPZ2+·Tart2- crystal is less defect free and suitable for NLO applications. Keywords: Organic salt; DFT; Vibrational spectroscopy; Hyperpolarizability; Second harmonic generation.
*Corresponding author email: [email protected] (R. Mathammal)
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1. Introduction Non-linear optical (NLO) crystals are highly attracted for optical applications such as frequency conversion, frequency mixing, optical data storage, electro-optical modulation and optical parametric oscillation [1, 2]. Organic materials have been of particular interest because of
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the nonlinear optical responses. In this broad class of materials, it is microscopic in origin, offering an opportunity to use theoretical modelling coupled with synthetic flexibility to design and produce novel materials [3].Other advantages of organic compound apart from synthesis and multifunctional substitutions is it has high resistance to optical damage making it a promising
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material for device applications [4]. Hence the need to synthesize organic NLO material and study its structural optical and spectral analysis becomes important. A SHG active organic salt is
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one of its kind guarantees for non-centrosymmetric molecular arrangement in crystals suitable for NLO applications [5]. Recently, the use of L-tartaric acid for the formation of non-centrosymmetric crystal structure has been reported [6]. It is a small aliphatic linear organic molecule, possesses large dipole moment, strong hydrogen bonds, wide transparency range and chiral structure [7]. The bulk crystal growth and NLO properties of L-tartaric acid has been reported elsewhere [8, 9] Investigating tartaric acid is considered important because it has the
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ability to combine with some organic bases due to chirality. The deprotonated anion, L-tartrate (from here on Tart) widely involved to form SHG salts with different cations such as L-Asparagine [10,11], L-Prolinium [12,13], Piperidinium, Pyridinium, Benzylammonium, 2-Aminopyrimidinium, 3-Hydroxypyridinium, Imidazolium [14]. The efficiency of nonlinear
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response from these combinations depends on the choice of cation. It suggests that the selection of different cations to form a salt with L-tartaric acid can improve the SHG activity of the
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organic salt. In this aspect, molecules of six membered ring structure, piperazine (PPZ) has been investigated with L-tartaric acid. During the combination of tartaric acid with piperazine, two proton is transferred from the carboxylic acid group to the piperazine nitrogen resulting piperazinium cation (PPZ2+) and tartrate anion (Tart2-). Tartrate anions provide a rigid environment for the incorporation of cations to form acentric salts i.e. NLO materials [15]. Bulk crystal growth, crystal structure, thermal, optical properties and SHG efficiency of different cations with L-tartaric acid has been investigated recently [16-19, 7]. In this paper, the crystal structure and physicochemical properties of piperazinium L-tartrate salt has been studied 2
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using different analytical tools such as single crystal X-ray diffraction, FTIR, Raman spectrometer, UV-Vis-NIR and fluorescence spectroscopy, phase sensitive multimeter and density functional theory. The obtained experimental and theoretical results were compared and discussed.
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2. Experimental Section 2.1. Crystal Growth
The precursors, piperazine and L- tartaric acid(Merck, 99%) were purchased and used
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without further purification. Single crystals of piperazinium L-tartrate (PPZ2+·Tart2-) were grown from slow evaporation of aqueous solution. Stoichiometric amount (1:1) of piperazine (0.86 g) and L- tartaric acid (1.50 g) was dissolved in deionised water. The solution was continuously
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stirred for 5 hours to ensure the homogeneity and then filtered using Whatman filter paper to remove the suspended particles. The final solution was covered with perforated foil and allowed for slow evaporation at room temperature. A good quality and optically transparent single crystals of piperazinium L-tartrate (PPZ2+·tart2-) were harvested after three weeks and it was used
2.2. Characterization
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for different characterisations. The photograph of as grown crystal is presented in Figure S1.
Single crystal X-ray diffraction experiment was carried out using a Bruker Kappa APEX II diffractometer equipped with graphite monochromater. Mo Kα radiation at λ=0.71073 Å was
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used for X-ray diffraction. Data were reduced using SAINT/XPREP (Bruker, 2004). Lorentz and polarisation corrections were included. All non-hydrogen atoms were found using the direct
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method analysis in SHELX-97 [20] and after several cycles of refinement, the positions of the hydrogen atoms were calculated and added to the refinement process. The single crystal results were used for molecular optimization and comparison of results obtained from DFT calculation. FTIR spectrum was recorded in the region 4000-400 cm-1 at a resolution of 2 cm-1 using a Perkin Elmer spectrometer at KBr phase. The FT-Raman spectrum was recorded in the frequency region 50-4000 cm-1 using BRUKER RFS27 spectrometer. The Perkin Elmer Lambda 35 spectrophotometer was used to record the UV-Vis-NIR spectrum in the range of 190-1100 nm at a scanning rate 960 nm/min. The spectrum was measured using water as a solvent. The 3
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fluorescence emission spectrum was recorded for liquid phase of PPZ2+·Tart2- using Perkin Elmer LS 45 spectrophotometer. The excitation wavelength used for this emission spectrum is 195 nm. Different solvents such as water, ethanol and methanol (polar protic), acetone (polar aprotic) were used. The dielectric measurement was performed using NumetriQ PSM 1735 phase
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sensitive multimeter interfaced with impedance analyser. A crystal thickness of 1.2 mm was coated with silver paste to obtain good conducting surface for dielectric measurement. The second harmonic generation (SHG) efficiency from microcrystalline powder of PPZ2+·Tart2- was measured using a Kurtz and Perry technique. The crystals were powdered to a uniform particle
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size ≈125 µm and then loaded in glass capillaries with an inner diameter of 600 µm. A QSwitched, mode Locked Nd:YAG laser with wavelength of 1064 nm and pulse width of 8 ns was
2.3. Computational Details
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used. The photodiode and oscilloscope assembly detect the light emitted from the sample.
Computational methods are significantly involved in providing first-hand information about structure- property relationship of optical materials. Theoretical calculations were performed using Gaussian 09 software packages [21]. The molecules were optimised at gas phase using a
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correlation function B3LYP with 6-311++G (d,p) basis set. The crystallographic information file (.CIF) obtained from single crystal XRD was used for molecular optimization. The molecule under investigation belongs to C1 point group symmetry having 32 atoms and 90 normal modes of vibration. The absence of imaginary frequencies in the optimised geometry
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ensures the true minimum on the potential energy surface. The unscaled vibrational frequencies, infrared intensities, Raman activities and depolarization ratios were obtained from DFT
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calculation. In order to fit the calculated and the experimental wavenumbers, the scale factor was introduced using a least square optimisation. All the vibrational frequencies were scaled at 0.956 to compensate the harmonic approximation. The scaled frequencies were deviated < 10 cm-1 with few exceptions from the experimental frequencies. Furthermore, the dipole moment, linear polarizability, hyperpolarizability, frontier molecular orbital energies of PPZ2+·Tart2- were calculated at B3LYP/6-311++G (d, p) level.
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4. Results and Discussion 4.1. Molecular Arrangements The PPZ2+·Tart2- crystallise in monoclinic noncentrosymmetric space group P21 with lattice
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parameter a = 6.4295 Å, b = 9.1364Å, c = 9.3643 Å, and β = 108.853˚, α=γ=90. The unit cell volume is 520.57 Å3 with Z=2 in the asymmetric unit. The crystallographic details and structural refinement parameters are presented in Table 1. The ORTEP plot of PPZ2+·Tart2- obtained from single crystal X-ray diffraction is presented in Figure 2 (b). The experimental bond length and
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bond angle values are in good agreement with the theoretical values (Table 2 and Table 3). The experimental and theoretical bond length and bond angle values are portrayed using Root Mean Square Deviation by Linear regression plot shown in Figure S2 and Figure S3.It is found that the
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value R2= 0.98508 for bond length and R2 =0.92106 for bond angle which is a very good correlation. Despite deprotonation of carboxylic group in the tartaric acid, the C–O bond in the carboxylate anions are strong and thus the experimental values match with the theoretical values C(5)-O(1), C(5)-O(2), C(8)-O(5), C(8)-O(6) (Table 4). The hydrogen of acid and nitrogen of base forms a good donor acceptor bridge forming a layered structure through intermolecular (N1-H14···O4 and
N2-H13···O1)
and
intramolecular
interactions
(O4-H11···O6
and
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O3-H16···O1). Moreover, the bond length of N(1)-H(5A) and N(1)-H(5B) is 0.94 and 0.87 respectively. The shorter bond length of tail end N(2)-H(6A) and N(2)-H(6B) is 0.97 and 0.89 respectively contributing a stable structure for PPZ2+·Tart2-.
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Optimised Geometry
Optimisation was completed when the optimising molecules reached its own minimum
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potential energy. The normal termination ensures the equilibrium structure of the molecule. The optimised structure using DFT calculation is shown in Figure 1. The geometry of hydroxyl group in the tartrate determines the optical rotation of tartaric acid. The in-plane and perpendicular arrangements of C7-O4 and C6-O3 (Figure 2) confirm the levorotatory of tartrate. Hydrogen Bonding Both inter and intramolecular hydrogen bonding is formed in the PPZ2+·Tart2- crystals. The intramolecular bond formed between hydroxyl group and carboxylate ions (O6-H11 and 5
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O1-H16) in the Tart2- is shown in Figure 2(a). A strong intermolecular hydrogen bonding is formed between carboxylic group in the L-tartaric acid and N-H in the piperazine. The carboxylic group in the L-tartaric acid losses its two hydrogens to the piperazine form a protonated piperazinium. The intermolecular hydrogen bonds are N1–H14···O4 and
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N2–H13···O1 with interaction energy of 218.50 kcal/mol. However, the individual monomer energy of L-tartaric acid is -168744.81 kcal/mol and piperazine is -380716.77kcal/mol. From this interaction energy, it can be said that the intermolecular interaction present in PPZ2+·Tart2- is
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strong. 4.2. Vibrational Analysis
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The FTIR spectrum of PPZ2+·Tart2- crystal shows the vibrational modes connected with piperazinium and L-tartrate ions. The hydrogen bond interaction in this crystal can be identified by assigning vibrational frequencies related to functional groups that involved in the hydrogen bond formation. The experimental and theoretical FTIR and FT-Raman spectrum of PPZ2+·Tart2are presented in Figures 4 and 5. The numerical harmonic vibrational analysis was performed for the optimised geometry. In agreement with C1 symmetry 90 normal modes of PPZ2+·Tart2- are
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distributed among the symmetry species as Γ3N-6 =61(in-plane)+ 29 (out-of-plane).The observed and calculated wavenumbers along with their relative IR intensity, Raman activity, and probable assignments with of PPZ2+·Tart2- molecule is given in the Table 5. The observed anharmonicity
N-H Vibrations
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in the real system was neglected for the calculated vibrations.
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The N-H stretching vibration of heterocyclic piperazinium can be traced around 3350 cm-1 in Raman Spectra [22]. In PPZ2+·Tart2-, N-H stretching vibration was observed at 3415 cm-1 and 3375 cm-1 in Raman spectra. The bending vibration of N-H was observed at 1389 cm-1. O-H Vibrations
The weak intramolecular hydrogen bonding between O-H of Tart2- and piperazinium nitrogen was observed. The O-H stretching vibration was observed at 3415 cm-1 in the FTIR spectrum. The counterpart of this vibration was not observed in the Raman spectrum. 6
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C-H Vibrations The C-H stretching vibration is observed above 3000 cm-1in IR [23]. In PPZ2+·Tart2-, the peak at 3015 cm-1 was assigned to C-H stretching of the heterocyclic ring in IR. The C-H bending
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vibrations occurs around 1416 cm-1 in the FTIR spectrum. This vibration appeared at 1608 cm-1 and 1440 cm-1. The strong peak appeared at 1437 cm-1 was assigned to the Raman spectrum. The C-H bending vibration also appeared at 1360 cm-1 in the FTIR and 1361 cm-1 in the Raman spectrum. The FTIR and Raman intensity is almost same at 1190 cm-1 and 1191 cm-1 for C-H
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vibrations. C-C Vibrations
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The carbon-carbon stretching vibration modes in aromatic compound are expected in the range 1430 cm-1 - 1625 cm-1.In the present work vibrations observed at 1603 cm-1 and 1440 cm-1 in IR is due to C-C stretching. In aliphatic compound C-C stretching is in the range 1000 cm-1 to 1200 cm-1.The peak at 1111 cm-1, 1189 cm-1 in IR and 1105 cm-1, 1165 cm-1 in Raman are due to C-C stretching.
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C-N Vibrations
The identification of C-N vibrations is a difficult task, due to overlapping of several bands.C-N stretching vibrations are observed in the region 1382 -1266 cm-1 [24].In the present work the
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bands are observed at 1390 cm-1 and 1226 cm-1 in FTIR. Carboxylic acid vibrations
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The vibrations observed at 1415 cm-1 and 1437 cm-1 in the FT-IR are due to stretching vibrations of the COO – presented in the PPZ2+·Tart2- . 4.3. UV-Vis NIR spectrum and Fluorescence Spectrum The optical transmittance spectrum of PPZ2+·Tart2- is shown in Figure 3(a). The lower cut off wavelength was observed at 195.19 nm. The PPZ2+·Tart2- show transmittance at entire UVVisible region in the aqueous medium. The L-tartaric shows strong absorption at 220-230 nm [8, 9]. The absorption of PPZ2+·Tart2- at 258.97 nm (red shift) is due to n- π* transition. The band 7
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gap energy of PPZ2+·Tart2- was calculated using the relation Eg=1.239x103/λmax eV [25] where λ is the lower cut off wavelength is at 195.19 nm and energy gap value is found to be Eg=6.351 eV indicates PPZ2+·Tart2- crystal possess wide band gap, which confirms the large transmittance in the visible region [26,27]. The absence of absorption above 300 nm recommends the
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PPZ2+·Tart2- crystals for NLO applications. Since the absorption, if any in the NLO material near the fundamental or second harmonic region will lead to the loss of conversion efficiency, it is necessary to have good optical transparency in an NLO crystal in the visible region. The theoretical UV spectrum generated from optimised structure is shown in Figure 3(b). The
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theoretical value in UV spectral data is 210.29 nm having excitation value 6.1903 eV of oscillator strength 0.0023 contributing to π - π * transition. The emission spectrum of PPZ2+·Tart2- at different solvents is shown in Figure 3(c). The emission peak is observed at 397
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nm for pure L-tartaric acid [8]. The emission peak of PPZ2+·Tart2- was observed at 410 nm (red shift) for water, ethanol and methanol (polar protic), acetone (polar aprotic) solvents. There is no significant variation in the emission spectrum at different solvents. 4.4 Dielectric Measurement
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4.4.1 Dielectric Constant
The noncentrosymmetric arrangement of molecules in the crystal has important properties such as piezoelectricity, nonlinear optical properties, ferroelectricity and pyro electricity [28, 29]. Since these properties are related to dielectric response of materials, it is significant to
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investigate the dielectric constant and dielectric loss of PPZ2+·Tart2- crystal. The variation of dielectric constant for the log frequency range 1.5-5.0 Hz is shown in Figure
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6. The dielectric constant steeply decreased with increasing frequency until 1.9 Hz and almost constant for the higher frequency sides. The dielectric constant at lower frequency follows linear relation with space-charge polarization. The electronic exchange of the number of ions in the crystal gives local displacement for the applied field, which gives the space charge polarisation. As the frequency increases, the space charges cannot sustain and follow accordance with the external applied field. Therefore, the polarisation decreases and exhibiting the reduction in the value of dielectric constant with increasing frequency [30].The characteristic of low dielectric
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constant at high frequency shows the optical quality of PPZ2+·Tart2- crystal with lesser defects. This phenomenon is important for NLO applications. 4.4.2 Dielectric Loss
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The dielectric loss studies the ability of materials to convert the electromagnetic energy into heat. The dielectric loss is high at time in which the polarisation lags behind the applied electric field. The variation of dielectric loss (tan δ) with frequency is shown in Figure 7. The dielectric loss decreases with increase of frequency. It indicates low dissipation of energy in the form of heat [18], which further confirms the quality of PPZ2+·Tart2- crystal. The low value of dielectric
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constant and dielectric loss at the higher frequency suggests PPZ2+·Tart2- crystal possess less defects and suitable for NLO applications.
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4.5. Second-Harmonic Generation Efficiency
The SHG effective non-linearity of the title compound was determined using Kurtz and Perry powder technique. It enables to measure the SHG effective non-linearity of new materials relative to KDP.A Q switched ND-YAG laser operating at 1064 and a laser input pulse of 1.9 mJ/pulse (pulse width: 8 ns, pulse rate: 10 Hz) was used for this measurement. The SHG output generated by the crystalline sample confirmed emission of green radiation of wavelength 532 nm
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from crystal powder. The measured output voltage from the PPZ2+·Tart2- and the KDP was 60 mV and 45 mV respectively. From this result, the SHG efficiency of PPZ2+·Tart2- is 1.3 times greater than that of standard KDP.
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Theoretical First Order Hyperpolarizability
The first-order hyperpolarizabilty can be defined as second order electric susceptibility per
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unit volume. The gas phase molecules exhibiting large hyperpolarzibility mean the system must be asymmetric and should contain polarizable electron donor and acceptor groups. The dipole moment (µ), mean polarizability (α), and the total first order hyperpolarizability (βtot) in terms of x, y, z components are given by the following equations: µ=( µ x2 + µ y2 + µ z2 ) ½
(1)
α=1/3(αxx + αyy+ αzz)
(2)
βtot= [(βxxx+βxyy+βxzz)2+(βyyy+βyzz+βyxx)2+(βzzz+βzxx+βzyy)2] ½ 9
(3)
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The βtot value of PPZ2+·Tart2- is 261.362797x10-33 and urea is 343.272x10-33. Theoretically, the hyperpolarizability value of PPZ2+·Tart2- is 0.76 times greater than that of standard urea.
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Theoretical hyperpolarizability of KDP is not available for comparison. The theoretical value of µ, α and βtot values are tabulated in Table S1. 4.6. Molecular Orbital Analysis
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The study of frontier molecular orbitals; highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is the promising method to realise the molecular interaction. The HOMO and LUMO plots are shown in Figure S4. The HOMO and LUMO act as
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an electron donor and electron acceptor respectively. Therefore, the energy of HOMO is directly related to ionisation potential and energy of LUMO is directly related to electron affinity. The eigenvalue of HOMO and LUMO and their energy gap reflect the chemical activity of the molecule. The calculated energies of PPZ2+·Tart2- are EHOMO=-6.631418 eV, ELUMO=0.5714394 eV and ∆EHOMO-LUMO=6.059979 eV. Additionally, other parameters such as electronegativity (χ)=0.13235, chemical hardness (η) =0.11135, softness (ζ) =4.490345 and electrophilicity index
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(ψ) =0.078655 are calculated. The HOMO in the PPZ2+·Tart2- compound is completely found on the tartrate anion (Tart2-) and LUMO is found completely on the piperzium cation. Since the anion and cation are distinct species connected by ionic interaction, each one has its own HOMO or LUMO. This distinct HOMO or LUMO on donor or acceptor is common in the ionic salt [31,
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32]. The predicted HOMO-LUMO energy gap is almost equal to UV optical band gap showing that the band gaps both in experimental as well calculated agree with each other. From the EHOMO
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and ELUMO values, it obvious that EHOMO occupy the compound, which possess most stable configuration. Compared with cyclic arrangement in the PPZ2+, the linear aliphatic Tart2possesses the most stable configuration due to the absence of ring strain. 4.7 Molecular Electrostatic Potential The molecular electrostatic potential (ESP) is the potential energy of a proton at a particular location near a molecule. The ESP plot of PPZ2+·Tart2- is shown in Figure S5. The Tart2- is more electronegative than the PPZ2+. Therefore, in PPZ2+·Tart2- compound, the electron flow is from 10
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Tart2- (nucleophile) to PPZ2+ (electrophile). The more colour differences indicate that the molecule is more polar in nature. The electron rich regions (negative potentials) electron poor regions (positive potentials) and neutral regions were represented by red, blue and green respectively. Potential increases in the sequence of red < orange < yellow < green < blue. The was traced at COO– in the PPZ2+·Tart2- compound. 5. Conclusion
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positive ESP value (blue colour) was traced at NH+ whereas negative ESP values (red colour)
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Single crystals of piperazinium L-tartrate (PPZ2+·Tart2-) were successfully grown from slow evaporation of aqueous solution. The strong inter and intra molecular interactions and short N-H bond lengths due to protonation of piperazine form a stable crystal structure in PPZ2+·Tart2-
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crystal. Quantum chemical calculations have helped to rationalize the experimental results. The observed red shift in absorption and fluorescence spectrum and spatial distribution of HOMO and LUMO on donor and acceptor moieties confirm the strong electrostatic interactions between donor and acceptor moieties. The fluorescence emission peak of PPZ2+·Tart2- was observed around 410 nm for different solvents (water, ethanol and methanol acetone). The dielectric studies prove that PPZ2+·Tart2- has lesser crystal defects .The FTIR and the Raman spectra
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confirm the observed hydrogen bonds and the proton transfer between the PPZ2+ and Tart2- ions. From molecular electrostatic potential it is evident that the electronegativity of L-tartrate is higher than the piperazinium ion. The SHG efficiency of PPZ2+·Tart2- is 1.3 times greater than
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the standard KDP crystal.
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Acknowledgements
The author N.Sudha is grateful to UGC SERO, Hyderabad for financial assistance under Minor Research Project. The authors are also thankful to Prof.P.K. Das Department of Inorganic and Physical Chemistry IISc Bangalore for extending SHG measurement, St.Joseph’s College Trichirappalli for providing spectral measurements and Sophisticated Analytical Instrumentation Facility (SAIF),IIT Chennai for XRD measurements.
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Properties Structure, vibrational spectra and phase transitions. J. Solid State Chem, 178 (2005) 2880-2896.
[20] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112-122. [21] M. J. Frisch et al. Gaussian 09, Revision A.1.Gaussian Inc. Wallingford, CT,2009. [22] G. Socrates, Infrared and Raman Characteristic Group Frequencies, John Wiley & Sons Ltd. 3rd Ed., (2001), England. [23] D.N. Sathyanarayana, Vibrational Spectroscopy Theory and Applications, New Age International, New Delhi, 1stEdition 2004. 13
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[24] Robert. M.Siverstein, Francis X. Webster and David J. Kiemle, Spectrometric Identification of Organic Compounds, John Wiley & Sons Ltd. 7rd Ed., (2005), England. [25] J.Tauc, R. Grigorovici, A.Vancu, Optical Properties and Electronic Structure of
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Amorphous Germanium. Physi Status Solidi B, 15 (1966) 627-637. [26] S.Boomadevi, R.Dhanasekaran, Synthesis, crystal growth and characterization of L-
pyrrolidone-2-carboxylic acid (L-PCA) crystals. J. Cryst Growth 261 (2004) 70-76.
[27] S.M Dharmaprakash, P. Mohan Rao, Dielectric properties of hydrated barium oxalate
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and barium cadmium oxalate crystals. J. Mater. Sci. Lett. 8 (1989) 1167-1168.
[28] C. P Smyth, Dielectric Behaviour and Structure, McGraw – Hill, New York, 1955. [29] Xitao Liu, Xinqiang Wang, Xin Yin, Shaojun Zhang, Lei Wang, Luyi Zhu, Guanghui
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Zhang Dong Xu, Characterization and strong piezoelectric response of an organometallic nonlinear optical crystal: CdHg(SCN)4(C2H6SO)2 J. Mater. Chem. C, 16 (2014) 723-730. [30] L. Guilbert, J. P. Salvestrini, M. D. Fontana, and Z. Czapla, Correlation between dielectric and electro-optic properties related to domain dynamics in RbHSeO4 crystals. Phys. Rev. B, 58 (1998) 2523-2528.
[31] Rajaboopathi Mani, Ivo B. Rietveld, Béatrice Nicolaï, Krishnakumar Varadharajan,
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Marjatta Louhi-Kultanen, Surumbarkuzhali Narasimhan, Fluorescence and physical properties of the organic salt 2-chloro-4-nitrobenzoate-3-ammonium-phenol. Chem. Phys 458 (2015) 52–61.
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[32] Rajaboopathi Mani, Ivo B. Rietveld, Krishnakumar Varadharajan, Marjatta LouhiKultanen, Senthilkumar Muthu, Fluorescence Properties Reinforced by Proton Transfer in the Salt 2,6-Diaminopyridinium Dihydrogen Phosphate. J.Phys.Chem. A, 118 (2014)
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6883–6892.
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ACCEPTED MANUSCRIPT Table. 1. Crystal data and structure refinement details of PPZ2+·Tart2- crystal. Table 2. Comparison of experimental and calculated bond lengths of PPZ2+·Tart2- crystal. Table 3. Comparison of experimental and calculated bond angles of PPZ2+·Tart2- crystal Table 4. C-O bond after deprotonation
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Table 5. Detailed assignment of fundamental vibrations of piperazinium L-tartrate (PPZ2+·Tart2-) by normal mode analysis based on SQM force field calculations.
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ACCEPTED MANUSCRIPT Figure Captions Fig.1. Optimised molecular structure of piperazinium -L-tartrate (PPZ2+·Tart2-) at gas phase. Fig. 2(a). Molecular structure and hydrogen bonding interactions of PPZ2+·Tart2- with atom numbering. Intermolecular interaction (N1-H14···O4 and N2-H13···O1) and intramolecular
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interaction (O4-H11···O6 and O3-H16···O1) are presented in PPZ2+·Tart2-. Fig.2(b).ORTEP plot of piperazinium L-tartrate crystal.
Fig. 3(a). UV-Vis NIR spectrum of piperazinium L-tartrate crystal at aqueous medium
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Fig 3(b). UV-Vis theoretical spectrum of piperazinium L-tartrate crystal
Fig 3(c). Fluorescence emission spectra of piperazinium L-tartrate in different solvents under
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195nm excitation
Fig. 4. Experimental (a) and calculated (b) FTIR spectrum of piperazinium L-tartrate crystal Fig. 5. Experimental (a) and calculated (b) FT-Raman spectrum of piperazinium L-tartrate crystal
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Fig. 6. Variation of dielectric constant with log frequency of piperazinium L-tartrate crystal
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Fig. 7. Variation of dielectric loss with log frequency of piperazinium L-tartrate crystal
ACCEPTED MANUSCRIPT Supporting Material Captions Fig. S1. Piperazinium L tartrate Crystal Fig S2 Root Mean Square Deviation by Linear regression plots of experimental and Calculated bond length
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Fig S3 Root Mean Square Deviation by Linear regression plots of experimental and Calculated bond angle
Fig. S4. HOMO (a) and LUMO (b) plot of isolated PPZ2+·Tart2- compound.
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Fig.S5. Space filled molecular electrostatic potential plot of piperazinium L-tartrate at gas phase Table S1
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Dipole moment (µ) and first-order hyperpolarizability (β) of PPZ2+·Tart2- derived from DFT calculationat 6-311++G (d,p) basis set.
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Empirical formula
C8 H16 N2 O6
Formula weight
236.23
Temperature
296(2) K
Wavelength
0.71073 Å
Crystal system, space group
Monoclinic, P21
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Table. 1. Crystal data and structure refinement details of PPZ2+·Tart2- crystal.
α = 90 deg. β = 108.8537 deg. γ = 90 deg.
Z, Calculated density
2, 1.507 Mg/m3
Absorption coefficient
0.129 mm-1
F(000) Crystal size Theta range for data collection
252 0.350 x 0.260 x 0.120 mm 2.298 to 25.000 deg
Limiting indices
-7<=h<=7, -10<=k<=10, -11<=l<=8
Reflections collected / unique
4146 / 1780 [R(int) = 0.0120]
Completeness to theta
25.000
Absorption correction
None
Refinement method
Full-matrix least-squares on F2
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Unit cell dimensions
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Volume
a = 6.4295(2) Å b = 9.1364(3) Å c = 9.3643(3) Å 520.57 A3
1780 / 1 / 169 1.149
Final R indices [I>2sigma(I)] R indices (all data) Absolute structure parameter
R1 = 0.0219, wR2 = 0.0638 R1 = 0.0221, wR2 = 0.0640 0.14(18)
Extinction coefficient
n/a
Largest diff. peak and hole
0.165 and -0.163 e.A-3
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Data / restraints / parameters Goodness-of-fit on F^2
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Table 2. Comparison of experimental and calculated bond lengths of PPZ2+·Tart2- crystal. Experimental bond length [Å]
Theoretical bond length [Å]
1.485
1.5130
C(1)-C(2)
1.499
1.5181
C(1)-H(1A)
0.9700
1.0879
C(1)-H(1B)
0.9700
1.0863
C(2)-N(2)
1.487
1.4987
C(2)-H(2A)
0.9700
1.0886
C(2)-H(2B)
0.9700
1.0901
C(3)-N(2)
1.488
1.4979
C(3)-C(4)
1.506
1.5183
C(3)-H(3A)
0.9700
1.0902
C(3)-H(3B)
0.9700
1.0885
C(4)-N(1)
1.491
C(4)-H(4A)
0.9700
C(4)-H(4B)
0.9700
C(5)-O(1)
1.252
C(5)-O(2)
1.253
C(5)-C(6)
1.537
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C(6)-O(3) C(6)-C(7) C(6)-H(6)
1.5439
1.413
1.4229
1.533
1.5409
0.9800
1.0943
1.417
1.4355
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C(7)-O(4) C(7)-C(8)
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C(1)-N(1)
1.533
1.5568
0.9800
1.0940
C(8)-O(5)
1.241
1.2482
C(8)-O(6)
1.251
1.2634
N(1)-H(5A)
0.94
1.0358
N(1)-H(5B)
0.87
1.0213
N(2)-H(6A)
0.97
1.0207
N(2)-H(6B)
0.89
1.0764
O(3)-H(8)
0.77
0.9721
O(4)-H(9)
0.86
0.9847
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C(7)-H(7)
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Atoms
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112.784 107.369 110.529 105.775 110.856 109.338 109.176 108.058 112.973 108.647 109.027 108.872 109.651 107.896 112.678 108.707 108.905 108.928 112.801 107.327 110.174 107.221 110.495 108.667 126.272 115.105 118.566 111.549 110.819 110.477 109.216 106.613 108.006 108.086 111.939
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109.77 109.7 109.7 109.7 109.7 108.2 111.11 109.4 109.4 109.4 109.4 108.0 110.11 109.6 109.6 109.6 109.6 108.2 110.96 109.4 109.4 109.4 109.4 108.0 125.97 116.57 117.46 110.74 110.97 110.48 108.2 108.2 108.2 110.82 109.89
Theoretical bond angle [deg]
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Experimental bond angle[deg]
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Atoms with numbering N(1)-C(1)-C(2) N(1)-C(1)-H(1A) C(2)-C(1)-H(1A) N(1)-C(1)-H(1B) C(2)-C(1)-H(1B) H(1A)-C(1)-H(1B) N(2)-C(2)-C(1) N(2)-C(2)-H(2A) C(1)-C(2)-H(2A) N(2)-C(2)-H(2B) C(1)-C(2)-H(2B) H(2A)-C(2)-H(2B) N(2)-C(3)-C(4) N(2)-C(3)-H(3A) C(4)-C(3)-H(3A) N(2)-C(3)-H(3B) C(4)-C(3)-H(3B) H(3A)-C(3)-H(3B) N(1)-C(4)-C(3) N(1)-C(4)-H(4A) C(3)-C(4)-H(4A) N(1)-C(4)-H(4B) C(3)-C(4)-H(4B) H(4A)-C(4)-H(4B) O(1)-C(5)-O(2) O(1)-C(5)-C(6) O(2)-C(5)-C(6) O(3)-C(6)-C(7) O(3)-C(6)-C(5) C(7)-C(6)-C(5) O(3)-C(6)-H(6) C(7)-C(6)-H(6) C(5)-C(6)-H(6) O(4)-C(7)-C(8) O(4)-C(7)-C(6)
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110.56 111.559 ACCEPTED MANUSCRIPT 108.5 109.205 108.5 108.338 108.5 107.643 125.98 128.095 117.54 114.411 116.48 117.491 110.1 110.376 109.8 105.824 104.5 105.67 113 109.063 111.93 110.026 105.6 109.922 109.5 108.43 112.3 110.108 106.5 108.430 111 108.255 105 104.257 104.8 101.250
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C(8)-C(7)-C(6) O(4)-C(7)-H(7) C(8)-C(7)-H(7) C(6)-C(7)-H(7) O(5)-C(8)-O(6) O(5)-C(8)-C(7) O(6)-C(8)-C(7) C(4)-N(1)-H(5A) C(1)-N(1)-H(5B) C(4)-N(1)-H(5B) H(2O)-N(1)-H(5B) C(2)-N(2)-C(3) C(2)-N(2)-H(6A) C(3)-N(2)-H(6A) C(2)-N(2)-H(6B) C(3)-N(2)-H(6B) H(5O)-N(2)-H(6B) C(6)-O(3)-H(8) C(7)-O(4)-H(9)
Table 4. C-O bond after deprotonation
Experimental bond length [Å] 1.252
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Atoms
C(5)-O(1)
Theoretical bond length [Å]
1.2418
1.253
1.2797
C(8)-O(5)
1.241
1.2482
C(8)-O(6)
1.251
1.2634
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19. 20. 21. 22. 23.
Calculated frequency with B3LYP/6-311G(d,p) force field (cm-1)
Infrared 3415 3375
Unscaled 3658 3483 3480 3429 3241 3178 3169 3155 3152 3116 3112 3100 3095 3057 3049 2542 1678 1634
3024 3015 3009 2972
2418 1608
1440
1610
1620 1615 1553 1516 1509
1549 1544 1485 1449 1443
Raman 0.5440 1.0938 1.9749 1.6239 0.8542 2.2259 0.9125 0.2347 1.4993 1.8390 1.5208 0.6040 0.2898 0.0941 0.6381 2.4208 1.2045 1.3675
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IR 0.9918 4.3732 7.4346 19.4078 3.0298 21.2018 33.0063 38.1886 20.2083 91.7641 9.8556 41.7430 8.9549 6.4946 38.2471 9.7065 58.1966 0.7693
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3245
Scaled 3497 3330 3327 3278 3098 3038 3030 3016 3013 2978 2975 2963 2959 2922 2915 2430 1604 1562
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Raman
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1. 2. 3 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
Observed frequencies (cm-1)
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S.No
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Table 5. Detailed assignment of fundamental vibrations of piperazinium L-tartrate (PPZ2+·Tart2-) by normal mode analysis based on SQM force field calculations.
4.8707 62.3583 87.6025 4.6091 60.9225
2.8753 0.5671 1.7619 9.4331 3.3936 19
% Potential Energy Distribution (PED)
ν OH (tar) (100) ν NH (pip) (99) ν NH (pip)(98) ν OH (tar) (86) ν NH (pip) (99) ν CH (pip) (96) ν CH (pip) (96) ν CH (pip)(94) ν CH (pip)(94) ν CH (pip)(94) ν CH (pip)(94) ν CH (pip)(96) ν CH (pip)(96) ν CH (tar)(94) ν CH (tar)(94) ν NH (pip)(98) β CH (pip)(89) ν C=O(tar),(58) β OH (tar)(18), β CH (tar)(10),βNH(pip)(7) ν C=O (pip)(84), β NH (pip)(5) β NH (pip)(97) β NH (pip)(90), β CH (pip)(7) β CH (pip)(84), β NH (pip)(7) β CH (pip)(90), β NH (pip)(8)
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1503 1499 1488 1453
1437 1433 1423 1389
46.5414 109.0279 149.4027 96.7885
2.7307 2.2250 1.997 4.5042
28.
1450
1386
4.9264
7.9575
29. 30. 31.
1438 1424 1422
1375 1361 1359
8.8745 0.3940 12.8160
43.1392 3.5108 2.7891
1401
1339
18.6712
1.6123
1415 1389
1360
1361
32. 1320
1377
1316
5.5697
34. 35. 36.
1303
1370 1361 1351
1310 1301 1292
0.5352 38.8264 80.1306
0.0809 9.6375 1.8346
37.
1348
1289
35.9013
1.4001
38.
1342
1283
39.
1335
1276
1318 1250 1241 1225 1215 1201 1100 1087 1076 1060
1260 1195 1186 1171 1162 1148 1052 1039 1029 1013
1166 1111 1070
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1191
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1226 1190
3.8416
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33.
40. 41. 42. 43. 44. 45. 46. 47. 48 49
β CH (pip)(90), β NH (pip)(8) β CH (pip)(97) β CH (pip)(97) β CH (pip)(83), ν CC (pip)(12), β NH (pip)(5) ν CC (pip)(87), β CH (pip)(7), β NH (pip)(5) β NH(pip)(90) , β CH (pip)(7) β CH (pip)(90), β OH (tar)(9) β OH (tar)(85), β CH (tar)(10), β CH (pip)(4) β OH(tar)(54) , β CH(tar) (28), ν CC (tar)(16) β C=O(tar)(37), β OH(tar)(27), ν CC (tar)(11), β CH(pip)(8) β CH (tar) (99) β CH(tar)(91) , β NH(pip)(8) ν CC(tar)(43) , β C=O(tar)(27), β CH(tar)13, β CH(tar)(10) β CH(pip)(59) ν CN (pip)(20), β NH (pip)(11) β CH(tar)(55), β OH(tar)(18), β CH(pip)(11) β CH(pip)(48), ν CC (tar)(38), β OH(tar)(7) β CH(tar)(82), β OH(tar)(17) β CH(64), β OH(tar)(30) β CH(pip)(80) β NH(pip)(10) β CH(pip)(97) β CH(tar)(89), β OH(tar)(8) β CH(pip)(89), β NH(pip)(7) ν CO(tar)(85), ν CC (tar)(15) ν CC (pip)(54), ν CN(pip)(40) β CH(pip)(56), β NH(pip)(41) β pip ring(91)
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1437
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24. 25. 26. 27.
35.2282
15.6156
25.4702
1.1862
117.5998 50.1769 11.0840 69.1327 24.1243 225.9197 5.6671 99.4696 2.2872 5.6681
15.7419 8.0890 9.9655 0.5316 0.1274 6.4327 3.7560 12.6403 4.5173 0.4730 20
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1056
1010
7.3851
4.4422
51
1051
1005
14.1124
26.2662
1035 975
989 932
315.7859 31.6042
7.6638 4.1347
970 896
927 856
2.8613 669.7706
4.6884 20.4164
887 877 870 860 839 823 791
848 838 832 822 802 787 756
11.7443 36.3965 58.8098 189.3917 350.7767 53.8783 44.2750
10.8188 5.9422 41.2258 2.4181 4.8205 1.0071 9.5044
789 699 650 619 600 596 535 487 480 473 447 411 376 342 261 253 239
754 668 621 592 574 570 511 466 459 452 427 393 359 327 250 242 228
1.7841 2.1570 16.7681 10.0437 31.0270 58.6554 14.8306 42.5862 310.5865 596.2339 719.8116 120.2899 2221.0949 5.0838 75.9341 3.3261 8.7968
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79
818 792
637 592
528 479 448 412 357
246
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840
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56 57 58 59 60 61 62
894
4.5453 2.6413 17.1931 9.6916 4.1130 2.1603 9.0474 1.8599 14.0145 14.6822 16.4194 7.6770 309.7548 118.0992 310.3482 113.2896 435.6031
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896
975
EP
54 55
976 956
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52 53
β CH(pip)(50), ν CC(pip)(26),v CO(tar)(21) v CO(tar)(48), δ CC(tar)(28), ν CO(tar)(10),β pip ring(6) δ pip ring(98) β HCOH(tar)(51), δ C=O(tar)(30), ν CC(14) τ pip ring(99) ν CC(tar)(58), βC=O(tar)(23), β OH (tar)(11) τHCCO(tar)(97) τ pip ring(95) τ pip ring(91) τ pip ring(87) δ CC(tar)(52), βCH(41) δ ring(96) βC=O(tar)(48), β pip ring(29), ν CC(pip)(12) δ pip ring(72), βC=O (tar)(25) τCCCO(tar)(99) δOH(99) τHCCO(98) δ pip ring(54), δOH (tar)(40) δOH(tar)(69), δpip ring(22) τHCCO(tar)(97) β OH(tar)(95) β OH(tar)(94) β pip ring(98) β pip ring(98) δ pip ring(97) τHCOH(tar)(96) τHCOH(tar)(94) ,δ pip ring(5) δ pip ring(98) β CO(tar)(89),δpip ring(7) δ pip ring(94)
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50
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86 87 88 89 90
67
17.0267 9.1362 1.0268 3.3413 10.8676 6.7437
170.1122 279.2326 107.1126 195.5331 75.3032 74.1001
98 84
94 80
702.7815 484.9670
299.4145 86.8274
β Tartrate as whole(97) δ C=O(tar)(87), δC-O(tar)(9) τHCCO(tar)(86), δ pip ring(6) τCCCO(tar)(90),τ pip ring(7) τ pip ring(97) δC=O(tar)(60), δOH(tar)(29), δ pip ring(7) τCCOH(tar)(87), τCCCO(tar)(5) β tar(96)
81 55 39
77 53 37
121.4764 109.4103 232.8385
99.9412 177.4255 101.3814
τ tar(96) τ tar(95) τ tar(94)
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106
206 186 140 128 120 97
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189 149
216 195 146 134 126 101
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80 81 82 83 84 85
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Abbreviations used :pip-Piperazine ,tar-Tartrate, ν – stretching; δ scissoring; β- in plane bending; τ-torsion
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Fig.1. Optimised molecular structure of piperazinium-L-tartrate (PPZ2+·Tart2-) at gas phase.
Fig.2 (a).Molecular structure and hydrogen bonding interactions of PPZ2+·Tart2-with atom numbering. Intermolecular interaction (N1-H14···O4and N2-H13···O1) and intramolecular interaction (O4-H11···O6 and O3-H16···O1) are presented in PPZ2+·Tart2-. 22
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Fig.2 (b).ORTEP plot of piperazinium L-tartrate crystal.
Fig. 3(a). UV-Vis NIR spectrum of piperazinium L-tartrate crystal at aqueous medium
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Fig 3(b). UV-Vis theoretical spectrum of piperazinium L-tartrate crystal
Fig 3(c). Fluorescence emission spectra of piperazinium L-tartrate in different solvents under 195nm excitation.
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Wavenumber[cm-1]
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Fig. 4. Experimental (a) and calculated (b) FTIR spectrum of piperazinium L-tartrate crystal
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Wavenumber[cm-1]
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Fig. 5.Experimental(a) and calculated (b) FT-Raman spectrum of piperazinium L-tartrate crystal
[
Fig. 6. Variation of dielectric constant with log frequency of piperazinium L-tartrate crystal 26
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Fig. 7. Variation of dielectric loss with log frequency of piperazinium L-tartrate crystal
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ACCEPTED MANUSCRIPT Highlights Piperazine –L-Tartrate salt type crystals were grown. Structural, Vibrational, Optical, Dielectric and SHG property were studied.
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Optimised Geometry, HOMO-LUMO,MESP and hyperpolarizability were discussed.
S0022-2860(16)31207-8
DOI:
10.1016/j.molstruc.2016.11.045
Reference:
MOLSTR 23146
To appear in:
Journal of Molecular Structure
Received Date: 3 June 2016 Revised Date:
11 November 2016
Accepted Date: 14 November 2016
Please cite this article as: R. Mathammal, N. Sudha, R. Shankar, M. Rajaboopathi, S. Janagi, B. Prabavathi, Growth and spectral analysis of piperazinium L-Tartrate salt: A combined experimental and theoretical approach, Journal of Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.11.045. 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.
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Graphical Abstract
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Growth and Spectral Analysis of Piperazinium L-Tartrate Salt: A Combined Experimental and Theoretical Approach R. Mathammala*, N. Sudhaa, R. Shankarb, M. Rajaboopathic,d, S. Janagia, B. Prabavathia a
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Department of Physics, Sri Sarada College for Women (Autonomous), Salem-636016, Tamilnadu, India
b
Department of Physics, Bharathiar University, Coimbatore-641046, Tamilnadu, India
Department of Physics, Periyar University, Salem-636011, Tamilnadu, India
d
State Key Laboratory of Crystal Materials,Shandong University,Jinan-250100,China
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Abstract
This report discusses crystal structure, molecular arrangements, vibrational analysis, UV-Vis-NIR spectrum, fluorescence emission and second harmonic generation (SHG) efficiency of piperazinium L-tartrate (PPZ2+·Tart2-) crystals with the support of theoretical analysis. A good optical quality PPZ2+·Tart2- crystals were grown from slow evaporation of aqueous
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solution. The PPZ2+·Tart2- crystal belongs to monoclinic system with non-centrosymmetric space group P21. The charge transfer from donor to acceptor moieties and corresponding changes in the bond lengths and bond angles have been observed. The observed functional group vibrations in the experimental FTIR and the Raman spectrum were assigned and compared with theoretical
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wavenumbers of PPZ2+·Tart2-.The electron distribution on the donor and acceptor in PPZ2+·Tart2has been clearly visualised using molecular electrostatic potential map. Compared with L-tartaric acid, red shift was observed in absorption and fluorescence spectrum. The low value of dielectric
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constant and dielectric loss at the higher frequency and its high second harmonic efficiency suggest PPZ2+·Tart2- crystal is less defect free and suitable for NLO applications. Keywords: Organic salt; DFT; Vibrational spectroscopy; Hyperpolarizability; Second harmonic generation.
*Corresponding author email: [email protected] (R. Mathammal)
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1. Introduction Non-linear optical (NLO) crystals are highly attracted for optical applications such as frequency conversion, frequency mixing, optical data storage, electro-optical modulation and optical parametric oscillation [1, 2]. Organic materials have been of particular interest because of
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the nonlinear optical responses. In this broad class of materials, it is microscopic in origin, offering an opportunity to use theoretical modelling coupled with synthetic flexibility to design and produce novel materials [3].Other advantages of organic compound apart from synthesis and multifunctional substitutions is it has high resistance to optical damage making it a promising
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material for device applications [4]. Hence the need to synthesize organic NLO material and study its structural optical and spectral analysis becomes important. A SHG active organic salt is
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one of its kind guarantees for non-centrosymmetric molecular arrangement in crystals suitable for NLO applications [5]. Recently, the use of L-tartaric acid for the formation of non-centrosymmetric crystal structure has been reported [6]. It is a small aliphatic linear organic molecule, possesses large dipole moment, strong hydrogen bonds, wide transparency range and chiral structure [7]. The bulk crystal growth and NLO properties of L-tartaric acid has been reported elsewhere [8, 9] Investigating tartaric acid is considered important because it has the
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ability to combine with some organic bases due to chirality. The deprotonated anion, L-tartrate (from here on Tart) widely involved to form SHG salts with different cations such as L-Asparagine [10,11], L-Prolinium [12,13], Piperidinium, Pyridinium, Benzylammonium, 2-Aminopyrimidinium, 3-Hydroxypyridinium, Imidazolium [14]. The efficiency of nonlinear
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response from these combinations depends on the choice of cation. It suggests that the selection of different cations to form a salt with L-tartaric acid can improve the SHG activity of the
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organic salt. In this aspect, molecules of six membered ring structure, piperazine (PPZ) has been investigated with L-tartaric acid. During the combination of tartaric acid with piperazine, two proton is transferred from the carboxylic acid group to the piperazine nitrogen resulting piperazinium cation (PPZ2+) and tartrate anion (Tart2-). Tartrate anions provide a rigid environment for the incorporation of cations to form acentric salts i.e. NLO materials [15]. Bulk crystal growth, crystal structure, thermal, optical properties and SHG efficiency of different cations with L-tartaric acid has been investigated recently [16-19, 7]. In this paper, the crystal structure and physicochemical properties of piperazinium L-tartrate salt has been studied 2
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using different analytical tools such as single crystal X-ray diffraction, FTIR, Raman spectrometer, UV-Vis-NIR and fluorescence spectroscopy, phase sensitive multimeter and density functional theory. The obtained experimental and theoretical results were compared and discussed.
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2. Experimental Section 2.1. Crystal Growth
The precursors, piperazine and L- tartaric acid(Merck, 99%) were purchased and used
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without further purification. Single crystals of piperazinium L-tartrate (PPZ2+·Tart2-) were grown from slow evaporation of aqueous solution. Stoichiometric amount (1:1) of piperazine (0.86 g) and L- tartaric acid (1.50 g) was dissolved in deionised water. The solution was continuously
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stirred for 5 hours to ensure the homogeneity and then filtered using Whatman filter paper to remove the suspended particles. The final solution was covered with perforated foil and allowed for slow evaporation at room temperature. A good quality and optically transparent single crystals of piperazinium L-tartrate (PPZ2+·tart2-) were harvested after three weeks and it was used
2.2. Characterization
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for different characterisations. The photograph of as grown crystal is presented in Figure S1.
Single crystal X-ray diffraction experiment was carried out using a Bruker Kappa APEX II diffractometer equipped with graphite monochromater. Mo Kα radiation at λ=0.71073 Å was
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used for X-ray diffraction. Data were reduced using SAINT/XPREP (Bruker, 2004). Lorentz and polarisation corrections were included. All non-hydrogen atoms were found using the direct
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method analysis in SHELX-97 [20] and after several cycles of refinement, the positions of the hydrogen atoms were calculated and added to the refinement process. The single crystal results were used for molecular optimization and comparison of results obtained from DFT calculation. FTIR spectrum was recorded in the region 4000-400 cm-1 at a resolution of 2 cm-1 using a Perkin Elmer spectrometer at KBr phase. The FT-Raman spectrum was recorded in the frequency region 50-4000 cm-1 using BRUKER RFS27 spectrometer. The Perkin Elmer Lambda 35 spectrophotometer was used to record the UV-Vis-NIR spectrum in the range of 190-1100 nm at a scanning rate 960 nm/min. The spectrum was measured using water as a solvent. The 3
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fluorescence emission spectrum was recorded for liquid phase of PPZ2+·Tart2- using Perkin Elmer LS 45 spectrophotometer. The excitation wavelength used for this emission spectrum is 195 nm. Different solvents such as water, ethanol and methanol (polar protic), acetone (polar aprotic) were used. The dielectric measurement was performed using NumetriQ PSM 1735 phase
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sensitive multimeter interfaced with impedance analyser. A crystal thickness of 1.2 mm was coated with silver paste to obtain good conducting surface for dielectric measurement. The second harmonic generation (SHG) efficiency from microcrystalline powder of PPZ2+·Tart2- was measured using a Kurtz and Perry technique. The crystals were powdered to a uniform particle
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size ≈125 µm and then loaded in glass capillaries with an inner diameter of 600 µm. A QSwitched, mode Locked Nd:YAG laser with wavelength of 1064 nm and pulse width of 8 ns was
2.3. Computational Details
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used. The photodiode and oscilloscope assembly detect the light emitted from the sample.
Computational methods are significantly involved in providing first-hand information about structure- property relationship of optical materials. Theoretical calculations were performed using Gaussian 09 software packages [21]. The molecules were optimised at gas phase using a
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correlation function B3LYP with 6-311++G (d,p) basis set. The crystallographic information file (.CIF) obtained from single crystal XRD was used for molecular optimization. The molecule under investigation belongs to C1 point group symmetry having 32 atoms and 90 normal modes of vibration. The absence of imaginary frequencies in the optimised geometry
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ensures the true minimum on the potential energy surface. The unscaled vibrational frequencies, infrared intensities, Raman activities and depolarization ratios were obtained from DFT
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calculation. In order to fit the calculated and the experimental wavenumbers, the scale factor was introduced using a least square optimisation. All the vibrational frequencies were scaled at 0.956 to compensate the harmonic approximation. The scaled frequencies were deviated < 10 cm-1 with few exceptions from the experimental frequencies. Furthermore, the dipole moment, linear polarizability, hyperpolarizability, frontier molecular orbital energies of PPZ2+·Tart2- were calculated at B3LYP/6-311++G (d, p) level.
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4. Results and Discussion 4.1. Molecular Arrangements The PPZ2+·Tart2- crystallise in monoclinic noncentrosymmetric space group P21 with lattice
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parameter a = 6.4295 Å, b = 9.1364Å, c = 9.3643 Å, and β = 108.853˚, α=γ=90. The unit cell volume is 520.57 Å3 with Z=2 in the asymmetric unit. The crystallographic details and structural refinement parameters are presented in Table 1. The ORTEP plot of PPZ2+·Tart2- obtained from single crystal X-ray diffraction is presented in Figure 2 (b). The experimental bond length and
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bond angle values are in good agreement with the theoretical values (Table 2 and Table 3). The experimental and theoretical bond length and bond angle values are portrayed using Root Mean Square Deviation by Linear regression plot shown in Figure S2 and Figure S3.It is found that the
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value R2= 0.98508 for bond length and R2 =0.92106 for bond angle which is a very good correlation. Despite deprotonation of carboxylic group in the tartaric acid, the C–O bond in the carboxylate anions are strong and thus the experimental values match with the theoretical values C(5)-O(1), C(5)-O(2), C(8)-O(5), C(8)-O(6) (Table 4). The hydrogen of acid and nitrogen of base forms a good donor acceptor bridge forming a layered structure through intermolecular (N1-H14···O4 and
N2-H13···O1)
and
intramolecular
interactions
(O4-H11···O6
and
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O3-H16···O1). Moreover, the bond length of N(1)-H(5A) and N(1)-H(5B) is 0.94 and 0.87 respectively. The shorter bond length of tail end N(2)-H(6A) and N(2)-H(6B) is 0.97 and 0.89 respectively contributing a stable structure for PPZ2+·Tart2-.
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Optimised Geometry
Optimisation was completed when the optimising molecules reached its own minimum
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potential energy. The normal termination ensures the equilibrium structure of the molecule. The optimised structure using DFT calculation is shown in Figure 1. The geometry of hydroxyl group in the tartrate determines the optical rotation of tartaric acid. The in-plane and perpendicular arrangements of C7-O4 and C6-O3 (Figure 2) confirm the levorotatory of tartrate. Hydrogen Bonding Both inter and intramolecular hydrogen bonding is formed in the PPZ2+·Tart2- crystals. The intramolecular bond formed between hydroxyl group and carboxylate ions (O6-H11 and 5
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O1-H16) in the Tart2- is shown in Figure 2(a). A strong intermolecular hydrogen bonding is formed between carboxylic group in the L-tartaric acid and N-H in the piperazine. The carboxylic group in the L-tartaric acid losses its two hydrogens to the piperazine form a protonated piperazinium. The intermolecular hydrogen bonds are N1–H14···O4 and
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N2–H13···O1 with interaction energy of 218.50 kcal/mol. However, the individual monomer energy of L-tartaric acid is -168744.81 kcal/mol and piperazine is -380716.77kcal/mol. From this interaction energy, it can be said that the intermolecular interaction present in PPZ2+·Tart2- is
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strong. 4.2. Vibrational Analysis
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The FTIR spectrum of PPZ2+·Tart2- crystal shows the vibrational modes connected with piperazinium and L-tartrate ions. The hydrogen bond interaction in this crystal can be identified by assigning vibrational frequencies related to functional groups that involved in the hydrogen bond formation. The experimental and theoretical FTIR and FT-Raman spectrum of PPZ2+·Tart2are presented in Figures 4 and 5. The numerical harmonic vibrational analysis was performed for the optimised geometry. In agreement with C1 symmetry 90 normal modes of PPZ2+·Tart2- are
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distributed among the symmetry species as Γ3N-6 =61(in-plane)+ 29 (out-of-plane).The observed and calculated wavenumbers along with their relative IR intensity, Raman activity, and probable assignments with of PPZ2+·Tart2- molecule is given in the Table 5. The observed anharmonicity
N-H Vibrations
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in the real system was neglected for the calculated vibrations.
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The N-H stretching vibration of heterocyclic piperazinium can be traced around 3350 cm-1 in Raman Spectra [22]. In PPZ2+·Tart2-, N-H stretching vibration was observed at 3415 cm-1 and 3375 cm-1 in Raman spectra. The bending vibration of N-H was observed at 1389 cm-1. O-H Vibrations
The weak intramolecular hydrogen bonding between O-H of Tart2- and piperazinium nitrogen was observed. The O-H stretching vibration was observed at 3415 cm-1 in the FTIR spectrum. The counterpart of this vibration was not observed in the Raman spectrum. 6
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C-H Vibrations The C-H stretching vibration is observed above 3000 cm-1in IR [23]. In PPZ2+·Tart2-, the peak at 3015 cm-1 was assigned to C-H stretching of the heterocyclic ring in IR. The C-H bending
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vibrations occurs around 1416 cm-1 in the FTIR spectrum. This vibration appeared at 1608 cm-1 and 1440 cm-1. The strong peak appeared at 1437 cm-1 was assigned to the Raman spectrum. The C-H bending vibration also appeared at 1360 cm-1 in the FTIR and 1361 cm-1 in the Raman spectrum. The FTIR and Raman intensity is almost same at 1190 cm-1 and 1191 cm-1 for C-H
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vibrations. C-C Vibrations
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The carbon-carbon stretching vibration modes in aromatic compound are expected in the range 1430 cm-1 - 1625 cm-1.In the present work vibrations observed at 1603 cm-1 and 1440 cm-1 in IR is due to C-C stretching. In aliphatic compound C-C stretching is in the range 1000 cm-1 to 1200 cm-1.The peak at 1111 cm-1, 1189 cm-1 in IR and 1105 cm-1, 1165 cm-1 in Raman are due to C-C stretching.
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C-N Vibrations
The identification of C-N vibrations is a difficult task, due to overlapping of several bands.C-N stretching vibrations are observed in the region 1382 -1266 cm-1 [24].In the present work the
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bands are observed at 1390 cm-1 and 1226 cm-1 in FTIR. Carboxylic acid vibrations
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The vibrations observed at 1415 cm-1 and 1437 cm-1 in the FT-IR are due to stretching vibrations of the COO – presented in the PPZ2+·Tart2- . 4.3. UV-Vis NIR spectrum and Fluorescence Spectrum The optical transmittance spectrum of PPZ2+·Tart2- is shown in Figure 3(a). The lower cut off wavelength was observed at 195.19 nm. The PPZ2+·Tart2- show transmittance at entire UVVisible region in the aqueous medium. The L-tartaric shows strong absorption at 220-230 nm [8, 9]. The absorption of PPZ2+·Tart2- at 258.97 nm (red shift) is due to n- π* transition. The band 7
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gap energy of PPZ2+·Tart2- was calculated using the relation Eg=1.239x103/λmax eV [25] where λ is the lower cut off wavelength is at 195.19 nm and energy gap value is found to be Eg=6.351 eV indicates PPZ2+·Tart2- crystal possess wide band gap, which confirms the large transmittance in the visible region [26,27]. The absence of absorption above 300 nm recommends the
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PPZ2+·Tart2- crystals for NLO applications. Since the absorption, if any in the NLO material near the fundamental or second harmonic region will lead to the loss of conversion efficiency, it is necessary to have good optical transparency in an NLO crystal in the visible region. The theoretical UV spectrum generated from optimised structure is shown in Figure 3(b). The
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theoretical value in UV spectral data is 210.29 nm having excitation value 6.1903 eV of oscillator strength 0.0023 contributing to π - π * transition. The emission spectrum of PPZ2+·Tart2- at different solvents is shown in Figure 3(c). The emission peak is observed at 397
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nm for pure L-tartaric acid [8]. The emission peak of PPZ2+·Tart2- was observed at 410 nm (red shift) for water, ethanol and methanol (polar protic), acetone (polar aprotic) solvents. There is no significant variation in the emission spectrum at different solvents. 4.4 Dielectric Measurement
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4.4.1 Dielectric Constant
The noncentrosymmetric arrangement of molecules in the crystal has important properties such as piezoelectricity, nonlinear optical properties, ferroelectricity and pyro electricity [28, 29]. Since these properties are related to dielectric response of materials, it is significant to
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investigate the dielectric constant and dielectric loss of PPZ2+·Tart2- crystal. The variation of dielectric constant for the log frequency range 1.5-5.0 Hz is shown in Figure
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6. The dielectric constant steeply decreased with increasing frequency until 1.9 Hz and almost constant for the higher frequency sides. The dielectric constant at lower frequency follows linear relation with space-charge polarization. The electronic exchange of the number of ions in the crystal gives local displacement for the applied field, which gives the space charge polarisation. As the frequency increases, the space charges cannot sustain and follow accordance with the external applied field. Therefore, the polarisation decreases and exhibiting the reduction in the value of dielectric constant with increasing frequency [30].The characteristic of low dielectric
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constant at high frequency shows the optical quality of PPZ2+·Tart2- crystal with lesser defects. This phenomenon is important for NLO applications. 4.4.2 Dielectric Loss
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The dielectric loss studies the ability of materials to convert the electromagnetic energy into heat. The dielectric loss is high at time in which the polarisation lags behind the applied electric field. The variation of dielectric loss (tan δ) with frequency is shown in Figure 7. The dielectric loss decreases with increase of frequency. It indicates low dissipation of energy in the form of heat [18], which further confirms the quality of PPZ2+·Tart2- crystal. The low value of dielectric
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constant and dielectric loss at the higher frequency suggests PPZ2+·Tart2- crystal possess less defects and suitable for NLO applications.
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4.5. Second-Harmonic Generation Efficiency
The SHG effective non-linearity of the title compound was determined using Kurtz and Perry powder technique. It enables to measure the SHG effective non-linearity of new materials relative to KDP.A Q switched ND-YAG laser operating at 1064 and a laser input pulse of 1.9 mJ/pulse (pulse width: 8 ns, pulse rate: 10 Hz) was used for this measurement. The SHG output generated by the crystalline sample confirmed emission of green radiation of wavelength 532 nm
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from crystal powder. The measured output voltage from the PPZ2+·Tart2- and the KDP was 60 mV and 45 mV respectively. From this result, the SHG efficiency of PPZ2+·Tart2- is 1.3 times greater than that of standard KDP.
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Theoretical First Order Hyperpolarizability
The first-order hyperpolarizabilty can be defined as second order electric susceptibility per
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unit volume. The gas phase molecules exhibiting large hyperpolarzibility mean the system must be asymmetric and should contain polarizable electron donor and acceptor groups. The dipole moment (µ), mean polarizability (α), and the total first order hyperpolarizability (βtot) in terms of x, y, z components are given by the following equations: µ=( µ x2 + µ y2 + µ z2 ) ½
(1)
α=1/3(αxx + αyy+ αzz)
(2)
βtot= [(βxxx+βxyy+βxzz)2+(βyyy+βyzz+βyxx)2+(βzzz+βzxx+βzyy)2] ½ 9
(3)
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The βtot value of PPZ2+·Tart2- is 261.362797x10-33 and urea is 343.272x10-33. Theoretically, the hyperpolarizability value of PPZ2+·Tart2- is 0.76 times greater than that of standard urea.
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Theoretical hyperpolarizability of KDP is not available for comparison. The theoretical value of µ, α and βtot values are tabulated in Table S1. 4.6. Molecular Orbital Analysis
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The study of frontier molecular orbitals; highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is the promising method to realise the molecular interaction. The HOMO and LUMO plots are shown in Figure S4. The HOMO and LUMO act as
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an electron donor and electron acceptor respectively. Therefore, the energy of HOMO is directly related to ionisation potential and energy of LUMO is directly related to electron affinity. The eigenvalue of HOMO and LUMO and their energy gap reflect the chemical activity of the molecule. The calculated energies of PPZ2+·Tart2- are EHOMO=-6.631418 eV, ELUMO=0.5714394 eV and ∆EHOMO-LUMO=6.059979 eV. Additionally, other parameters such as electronegativity (χ)=0.13235, chemical hardness (η) =0.11135, softness (ζ) =4.490345 and electrophilicity index
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(ψ) =0.078655 are calculated. The HOMO in the PPZ2+·Tart2- compound is completely found on the tartrate anion (Tart2-) and LUMO is found completely on the piperzium cation. Since the anion and cation are distinct species connected by ionic interaction, each one has its own HOMO or LUMO. This distinct HOMO or LUMO on donor or acceptor is common in the ionic salt [31,
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32]. The predicted HOMO-LUMO energy gap is almost equal to UV optical band gap showing that the band gaps both in experimental as well calculated agree with each other. From the EHOMO
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and ELUMO values, it obvious that EHOMO occupy the compound, which possess most stable configuration. Compared with cyclic arrangement in the PPZ2+, the linear aliphatic Tart2possesses the most stable configuration due to the absence of ring strain. 4.7 Molecular Electrostatic Potential The molecular electrostatic potential (ESP) is the potential energy of a proton at a particular location near a molecule. The ESP plot of PPZ2+·Tart2- is shown in Figure S5. The Tart2- is more electronegative than the PPZ2+. Therefore, in PPZ2+·Tart2- compound, the electron flow is from 10
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Tart2- (nucleophile) to PPZ2+ (electrophile). The more colour differences indicate that the molecule is more polar in nature. The electron rich regions (negative potentials) electron poor regions (positive potentials) and neutral regions were represented by red, blue and green respectively. Potential increases in the sequence of red < orange < yellow < green < blue. The was traced at COO– in the PPZ2+·Tart2- compound. 5. Conclusion
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positive ESP value (blue colour) was traced at NH+ whereas negative ESP values (red colour)
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Single crystals of piperazinium L-tartrate (PPZ2+·Tart2-) were successfully grown from slow evaporation of aqueous solution. The strong inter and intra molecular interactions and short N-H bond lengths due to protonation of piperazine form a stable crystal structure in PPZ2+·Tart2-
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crystal. Quantum chemical calculations have helped to rationalize the experimental results. The observed red shift in absorption and fluorescence spectrum and spatial distribution of HOMO and LUMO on donor and acceptor moieties confirm the strong electrostatic interactions between donor and acceptor moieties. The fluorescence emission peak of PPZ2+·Tart2- was observed around 410 nm for different solvents (water, ethanol and methanol acetone). The dielectric studies prove that PPZ2+·Tart2- has lesser crystal defects .The FTIR and the Raman spectra
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confirm the observed hydrogen bonds and the proton transfer between the PPZ2+ and Tart2- ions. From molecular electrostatic potential it is evident that the electronegativity of L-tartrate is higher than the piperazinium ion. The SHG efficiency of PPZ2+·Tart2- is 1.3 times greater than
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the standard KDP crystal.
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Acknowledgements
The author N.Sudha is grateful to UGC SERO, Hyderabad for financial assistance under Minor Research Project. The authors are also thankful to Prof.P.K. Das Department of Inorganic and Physical Chemistry IISc Bangalore for extending SHG measurement, St.Joseph’s College Trichirappalli for providing spectral measurements and Sophisticated Analytical Instrumentation Facility (SAIF),IIT Chennai for XRD measurements.
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Zhang Dong Xu, Characterization and strong piezoelectric response of an organometallic nonlinear optical crystal: CdHg(SCN)4(C2H6SO)2 J. Mater. Chem. C, 16 (2014) 723-730. [30] L. Guilbert, J. P. Salvestrini, M. D. Fontana, and Z. Czapla, Correlation between dielectric and electro-optic properties related to domain dynamics in RbHSeO4 crystals. Phys. Rev. B, 58 (1998) 2523-2528.
[31] Rajaboopathi Mani, Ivo B. Rietveld, Béatrice Nicolaï, Krishnakumar Varadharajan,
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Marjatta Louhi-Kultanen, Surumbarkuzhali Narasimhan, Fluorescence and physical properties of the organic salt 2-chloro-4-nitrobenzoate-3-ammonium-phenol. Chem. Phys 458 (2015) 52–61.
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[32] Rajaboopathi Mani, Ivo B. Rietveld, Krishnakumar Varadharajan, Marjatta LouhiKultanen, Senthilkumar Muthu, Fluorescence Properties Reinforced by Proton Transfer in the Salt 2,6-Diaminopyridinium Dihydrogen Phosphate. J.Phys.Chem. A, 118 (2014)
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6883–6892.
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ACCEPTED MANUSCRIPT Table. 1. Crystal data and structure refinement details of PPZ2+·Tart2- crystal. Table 2. Comparison of experimental and calculated bond lengths of PPZ2+·Tart2- crystal. Table 3. Comparison of experimental and calculated bond angles of PPZ2+·Tart2- crystal Table 4. C-O bond after deprotonation
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Table 5. Detailed assignment of fundamental vibrations of piperazinium L-tartrate (PPZ2+·Tart2-) by normal mode analysis based on SQM force field calculations.
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ACCEPTED MANUSCRIPT Figure Captions Fig.1. Optimised molecular structure of piperazinium -L-tartrate (PPZ2+·Tart2-) at gas phase. Fig. 2(a). Molecular structure and hydrogen bonding interactions of PPZ2+·Tart2- with atom numbering. Intermolecular interaction (N1-H14···O4 and N2-H13···O1) and intramolecular
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interaction (O4-H11···O6 and O3-H16···O1) are presented in PPZ2+·Tart2-. Fig.2(b).ORTEP plot of piperazinium L-tartrate crystal.
Fig. 3(a). UV-Vis NIR spectrum of piperazinium L-tartrate crystal at aqueous medium
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Fig 3(b). UV-Vis theoretical spectrum of piperazinium L-tartrate crystal
Fig 3(c). Fluorescence emission spectra of piperazinium L-tartrate in different solvents under
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195nm excitation
Fig. 4. Experimental (a) and calculated (b) FTIR spectrum of piperazinium L-tartrate crystal Fig. 5. Experimental (a) and calculated (b) FT-Raman spectrum of piperazinium L-tartrate crystal
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Fig. 6. Variation of dielectric constant with log frequency of piperazinium L-tartrate crystal
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Fig. 7. Variation of dielectric loss with log frequency of piperazinium L-tartrate crystal
ACCEPTED MANUSCRIPT Supporting Material Captions Fig. S1. Piperazinium L tartrate Crystal Fig S2 Root Mean Square Deviation by Linear regression plots of experimental and Calculated bond length
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Fig S3 Root Mean Square Deviation by Linear regression plots of experimental and Calculated bond angle
Fig. S4. HOMO (a) and LUMO (b) plot of isolated PPZ2+·Tart2- compound.
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Fig.S5. Space filled molecular electrostatic potential plot of piperazinium L-tartrate at gas phase Table S1
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Dipole moment (µ) and first-order hyperpolarizability (β) of PPZ2+·Tart2- derived from DFT calculationat 6-311++G (d,p) basis set.
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Empirical formula
C8 H16 N2 O6
Formula weight
236.23
Temperature
296(2) K
Wavelength
0.71073 Å
Crystal system, space group
Monoclinic, P21
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Table. 1. Crystal data and structure refinement details of PPZ2+·Tart2- crystal.
α = 90 deg. β = 108.8537 deg. γ = 90 deg.
Z, Calculated density
2, 1.507 Mg/m3
Absorption coefficient
0.129 mm-1
F(000) Crystal size Theta range for data collection
252 0.350 x 0.260 x 0.120 mm 2.298 to 25.000 deg
Limiting indices
-7<=h<=7, -10<=k<=10, -11<=l<=8
Reflections collected / unique
4146 / 1780 [R(int) = 0.0120]
Completeness to theta
25.000
Absorption correction
None
Refinement method
Full-matrix least-squares on F2
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Unit cell dimensions
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Volume
a = 6.4295(2) Å b = 9.1364(3) Å c = 9.3643(3) Å 520.57 A3
1780 / 1 / 169 1.149
Final R indices [I>2sigma(I)] R indices (all data) Absolute structure parameter
R1 = 0.0219, wR2 = 0.0638 R1 = 0.0221, wR2 = 0.0640 0.14(18)
Extinction coefficient
n/a
Largest diff. peak and hole
0.165 and -0.163 e.A-3
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Data / restraints / parameters Goodness-of-fit on F^2
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Table 2. Comparison of experimental and calculated bond lengths of PPZ2+·Tart2- crystal. Experimental bond length [Å]
Theoretical bond length [Å]
1.485
1.5130
C(1)-C(2)
1.499
1.5181
C(1)-H(1A)
0.9700
1.0879
C(1)-H(1B)
0.9700
1.0863
C(2)-N(2)
1.487
1.4987
C(2)-H(2A)
0.9700
1.0886
C(2)-H(2B)
0.9700
1.0901
C(3)-N(2)
1.488
1.4979
C(3)-C(4)
1.506
1.5183
C(3)-H(3A)
0.9700
1.0902
C(3)-H(3B)
0.9700
1.0885
C(4)-N(1)
1.491
C(4)-H(4A)
0.9700
C(4)-H(4B)
0.9700
C(5)-O(1)
1.252
C(5)-O(2)
1.253
C(5)-C(6)
1.537
M AN U 1.5124 1.0878 1.0879 1.2418 1.2797
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C(6)-O(3) C(6)-C(7) C(6)-H(6)
1.5439
1.413
1.4229
1.533
1.5409
0.9800
1.0943
1.417
1.4355
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C(7)-O(4) C(7)-C(8)
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C(1)-N(1)
1.533
1.5568
0.9800
1.0940
C(8)-O(5)
1.241
1.2482
C(8)-O(6)
1.251
1.2634
N(1)-H(5A)
0.94
1.0358
N(1)-H(5B)
0.87
1.0213
N(2)-H(6A)
0.97
1.0207
N(2)-H(6B)
0.89
1.0764
O(3)-H(8)
0.77
0.9721
O(4)-H(9)
0.86
0.9847
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C(7)-H(7)
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Atoms
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ACCEPTED MANUSCRIPT Table 3. Comparison of experimental and calculated bond angles of PPZ2+·Tart2- crystal.
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112.784 107.369 110.529 105.775 110.856 109.338 109.176 108.058 112.973 108.647 109.027 108.872 109.651 107.896 112.678 108.707 108.905 108.928 112.801 107.327 110.174 107.221 110.495 108.667 126.272 115.105 118.566 111.549 110.819 110.477 109.216 106.613 108.006 108.086 111.939
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109.77 109.7 109.7 109.7 109.7 108.2 111.11 109.4 109.4 109.4 109.4 108.0 110.11 109.6 109.6 109.6 109.6 108.2 110.96 109.4 109.4 109.4 109.4 108.0 125.97 116.57 117.46 110.74 110.97 110.48 108.2 108.2 108.2 110.82 109.89
Theoretical bond angle [deg]
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Experimental bond angle[deg]
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Atoms with numbering N(1)-C(1)-C(2) N(1)-C(1)-H(1A) C(2)-C(1)-H(1A) N(1)-C(1)-H(1B) C(2)-C(1)-H(1B) H(1A)-C(1)-H(1B) N(2)-C(2)-C(1) N(2)-C(2)-H(2A) C(1)-C(2)-H(2A) N(2)-C(2)-H(2B) C(1)-C(2)-H(2B) H(2A)-C(2)-H(2B) N(2)-C(3)-C(4) N(2)-C(3)-H(3A) C(4)-C(3)-H(3A) N(2)-C(3)-H(3B) C(4)-C(3)-H(3B) H(3A)-C(3)-H(3B) N(1)-C(4)-C(3) N(1)-C(4)-H(4A) C(3)-C(4)-H(4A) N(1)-C(4)-H(4B) C(3)-C(4)-H(4B) H(4A)-C(4)-H(4B) O(1)-C(5)-O(2) O(1)-C(5)-C(6) O(2)-C(5)-C(6) O(3)-C(6)-C(7) O(3)-C(6)-C(5) C(7)-C(6)-C(5) O(3)-C(6)-H(6) C(7)-C(6)-H(6) C(5)-C(6)-H(6) O(4)-C(7)-C(8) O(4)-C(7)-C(6)
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110.56 111.559 ACCEPTED MANUSCRIPT 108.5 109.205 108.5 108.338 108.5 107.643 125.98 128.095 117.54 114.411 116.48 117.491 110.1 110.376 109.8 105.824 104.5 105.67 113 109.063 111.93 110.026 105.6 109.922 109.5 108.43 112.3 110.108 106.5 108.430 111 108.255 105 104.257 104.8 101.250
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C(8)-C(7)-C(6) O(4)-C(7)-H(7) C(8)-C(7)-H(7) C(6)-C(7)-H(7) O(5)-C(8)-O(6) O(5)-C(8)-C(7) O(6)-C(8)-C(7) C(4)-N(1)-H(5A) C(1)-N(1)-H(5B) C(4)-N(1)-H(5B) H(2O)-N(1)-H(5B) C(2)-N(2)-C(3) C(2)-N(2)-H(6A) C(3)-N(2)-H(6A) C(2)-N(2)-H(6B) C(3)-N(2)-H(6B) H(5O)-N(2)-H(6B) C(6)-O(3)-H(8) C(7)-O(4)-H(9)
Table 4. C-O bond after deprotonation
Experimental bond length [Å] 1.252
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Atoms
C(5)-O(1)
Theoretical bond length [Å]
1.2418
1.253
1.2797
C(8)-O(5)
1.241
1.2482
C(8)-O(6)
1.251
1.2634
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19. 20. 21. 22. 23.
Calculated frequency with B3LYP/6-311G(d,p) force field (cm-1)
Infrared 3415 3375
Unscaled 3658 3483 3480 3429 3241 3178 3169 3155 3152 3116 3112 3100 3095 3057 3049 2542 1678 1634
3024 3015 3009 2972
2418 1608
1440
1610
1620 1615 1553 1516 1509
1549 1544 1485 1449 1443
Raman 0.5440 1.0938 1.9749 1.6239 0.8542 2.2259 0.9125 0.2347 1.4993 1.8390 1.5208 0.6040 0.2898 0.0941 0.6381 2.4208 1.2045 1.3675
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IR 0.9918 4.3732 7.4346 19.4078 3.0298 21.2018 33.0063 38.1886 20.2083 91.7641 9.8556 41.7430 8.9549 6.4946 38.2471 9.7065 58.1966 0.7693
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3245
Scaled 3497 3330 3327 3278 3098 3038 3030 3016 3013 2978 2975 2963 2959 2922 2915 2430 1604 1562
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Raman
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1. 2. 3 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
Observed frequencies (cm-1)
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S.No
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Table 5. Detailed assignment of fundamental vibrations of piperazinium L-tartrate (PPZ2+·Tart2-) by normal mode analysis based on SQM force field calculations.
4.8707 62.3583 87.6025 4.6091 60.9225
2.8753 0.5671 1.7619 9.4331 3.3936 19
% Potential Energy Distribution (PED)
ν OH (tar) (100) ν NH (pip) (99) ν NH (pip)(98) ν OH (tar) (86) ν NH (pip) (99) ν CH (pip) (96) ν CH (pip) (96) ν CH (pip)(94) ν CH (pip)(94) ν CH (pip)(94) ν CH (pip)(94) ν CH (pip)(96) ν CH (pip)(96) ν CH (tar)(94) ν CH (tar)(94) ν NH (pip)(98) β CH (pip)(89) ν C=O(tar),(58) β OH (tar)(18), β CH (tar)(10),βNH(pip)(7) ν C=O (pip)(84), β NH (pip)(5) β NH (pip)(97) β NH (pip)(90), β CH (pip)(7) β CH (pip)(84), β NH (pip)(7) β CH (pip)(90), β NH (pip)(8)
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1503 1499 1488 1453
1437 1433 1423 1389
46.5414 109.0279 149.4027 96.7885
2.7307 2.2250 1.997 4.5042
28.
1450
1386
4.9264
7.9575
29. 30. 31.
1438 1424 1422
1375 1361 1359
8.8745 0.3940 12.8160
43.1392 3.5108 2.7891
1401
1339
18.6712
1.6123
1415 1389
1360
1361
32. 1320
1377
1316
5.5697
34. 35. 36.
1303
1370 1361 1351
1310 1301 1292
0.5352 38.8264 80.1306
0.0809 9.6375 1.8346
37.
1348
1289
35.9013
1.4001
38.
1342
1283
39.
1335
1276
1318 1250 1241 1225 1215 1201 1100 1087 1076 1060
1260 1195 1186 1171 1162 1148 1052 1039 1029 1013
1166 1111 1070
1016
1045
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1191
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1226 1190
3.8416
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33.
40. 41. 42. 43. 44. 45. 46. 47. 48 49
β CH (pip)(90), β NH (pip)(8) β CH (pip)(97) β CH (pip)(97) β CH (pip)(83), ν CC (pip)(12), β NH (pip)(5) ν CC (pip)(87), β CH (pip)(7), β NH (pip)(5) β NH(pip)(90) , β CH (pip)(7) β CH (pip)(90), β OH (tar)(9) β OH (tar)(85), β CH (tar)(10), β CH (pip)(4) β OH(tar)(54) , β CH(tar) (28), ν CC (tar)(16) β C=O(tar)(37), β OH(tar)(27), ν CC (tar)(11), β CH(pip)(8) β CH (tar) (99) β CH(tar)(91) , β NH(pip)(8) ν CC(tar)(43) , β C=O(tar)(27), β CH(tar)13, β CH(tar)(10) β CH(pip)(59) ν CN (pip)(20), β NH (pip)(11) β CH(tar)(55), β OH(tar)(18), β CH(pip)(11) β CH(pip)(48), ν CC (tar)(38), β OH(tar)(7) β CH(tar)(82), β OH(tar)(17) β CH(64), β OH(tar)(30) β CH(pip)(80) β NH(pip)(10) β CH(pip)(97) β CH(tar)(89), β OH(tar)(8) β CH(pip)(89), β NH(pip)(7) ν CO(tar)(85), ν CC (tar)(15) ν CC (pip)(54), ν CN(pip)(40) β CH(pip)(56), β NH(pip)(41) β pip ring(91)
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1437
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24. 25. 26. 27.
35.2282
15.6156
25.4702
1.1862
117.5998 50.1769 11.0840 69.1327 24.1243 225.9197 5.6671 99.4696 2.2872 5.6681
15.7419 8.0890 9.9655 0.5316 0.1274 6.4327 3.7560 12.6403 4.5173 0.4730 20
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1056
1010
7.3851
4.4422
51
1051
1005
14.1124
26.2662
1035 975
989 932
315.7859 31.6042
7.6638 4.1347
970 896
927 856
2.8613 669.7706
4.6884 20.4164
887 877 870 860 839 823 791
848 838 832 822 802 787 756
11.7443 36.3965 58.8098 189.3917 350.7767 53.8783 44.2750
10.8188 5.9422 41.2258 2.4181 4.8205 1.0071 9.5044
789 699 650 619 600 596 535 487 480 473 447 411 376 342 261 253 239
754 668 621 592 574 570 511 466 459 452 427 393 359 327 250 242 228
1.7841 2.1570 16.7681 10.0437 31.0270 58.6554 14.8306 42.5862 310.5865 596.2339 719.8116 120.2899 2221.0949 5.0838 75.9341 3.3261 8.7968
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79
818 792
637 592
528 479 448 412 357
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840
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56 57 58 59 60 61 62
894
4.5453 2.6413 17.1931 9.6916 4.1130 2.1603 9.0474 1.8599 14.0145 14.6822 16.4194 7.6770 309.7548 118.0992 310.3482 113.2896 435.6031
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896
975
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54 55
976 956
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52 53
β CH(pip)(50), ν CC(pip)(26),v CO(tar)(21) v CO(tar)(48), δ CC(tar)(28), ν CO(tar)(10),β pip ring(6) δ pip ring(98) β HCOH(tar)(51), δ C=O(tar)(30), ν CC(14) τ pip ring(99) ν CC(tar)(58), βC=O(tar)(23), β OH (tar)(11) τHCCO(tar)(97) τ pip ring(95) τ pip ring(91) τ pip ring(87) δ CC(tar)(52), βCH(41) δ ring(96) βC=O(tar)(48), β pip ring(29), ν CC(pip)(12) δ pip ring(72), βC=O (tar)(25) τCCCO(tar)(99) δOH(99) τHCCO(98) δ pip ring(54), δOH (tar)(40) δOH(tar)(69), δpip ring(22) τHCCO(tar)(97) β OH(tar)(95) β OH(tar)(94) β pip ring(98) β pip ring(98) δ pip ring(97) τHCOH(tar)(96) τHCOH(tar)(94) ,δ pip ring(5) δ pip ring(98) β CO(tar)(89),δpip ring(7) δ pip ring(94)
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50
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86 87 88 89 90
67
17.0267 9.1362 1.0268 3.3413 10.8676 6.7437
170.1122 279.2326 107.1126 195.5331 75.3032 74.1001
98 84
94 80
702.7815 484.9670
299.4145 86.8274
β Tartrate as whole(97) δ C=O(tar)(87), δC-O(tar)(9) τHCCO(tar)(86), δ pip ring(6) τCCCO(tar)(90),τ pip ring(7) τ pip ring(97) δC=O(tar)(60), δOH(tar)(29), δ pip ring(7) τCCOH(tar)(87), τCCCO(tar)(5) β tar(96)
81 55 39
77 53 37
121.4764 109.4103 232.8385
99.9412 177.4255 101.3814
τ tar(96) τ tar(95) τ tar(94)
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106
206 186 140 128 120 97
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189 149
216 195 146 134 126 101
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80 81 82 83 84 85
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Abbreviations used :pip-Piperazine ,tar-Tartrate, ν – stretching; δ scissoring; β- in plane bending; τ-torsion
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Fig.1. Optimised molecular structure of piperazinium-L-tartrate (PPZ2+·Tart2-) at gas phase.
Fig.2 (a).Molecular structure and hydrogen bonding interactions of PPZ2+·Tart2-with atom numbering. Intermolecular interaction (N1-H14···O4and N2-H13···O1) and intramolecular interaction (O4-H11···O6 and O3-H16···O1) are presented in PPZ2+·Tart2-. 22
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Fig.2 (b).ORTEP plot of piperazinium L-tartrate crystal.
Fig. 3(a). UV-Vis NIR spectrum of piperazinium L-tartrate crystal at aqueous medium
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Fig 3(b). UV-Vis theoretical spectrum of piperazinium L-tartrate crystal
Fig 3(c). Fluorescence emission spectra of piperazinium L-tartrate in different solvents under 195nm excitation.
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Wavenumber[cm-1]
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Fig. 4. Experimental (a) and calculated (b) FTIR spectrum of piperazinium L-tartrate crystal
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Wavenumber[cm-1]
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Fig. 5.Experimental(a) and calculated (b) FT-Raman spectrum of piperazinium L-tartrate crystal
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Fig. 6. Variation of dielectric constant with log frequency of piperazinium L-tartrate crystal 26
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Fig. 7. Variation of dielectric loss with log frequency of piperazinium L-tartrate crystal
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.
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ACCEPTED MANUSCRIPT Highlights Piperazine –L-Tartrate salt type crystals were grown. Structural, Vibrational, Optical, Dielectric and SHG property were studied.
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Optimised Geometry, HOMO-LUMO,MESP and hyperpolarizability were discussed.