Synthesis, crystal structure, and 19F, 1H NMR investigation of the first compound of indium(III) with an amino acid

Accepted Manuscript Title: Synthesis, crystal structure, and 19 F, 1 H NMR investigation of the first compound of indium(III) with an amino acid Authors: V.Ya. Kavun, R.L. Davidovich, A.A. Udovenko, M.M. Polyantsev, V.B. Logvinova PII: DOI: Reference:

S0022-1139(18)30153-2 https://doi.org/10.1016/j.jfluchem.2018.05.006 FLUOR 9169

To appear in:

FLUOR

Received date: Revised date: Accepted date:

11-4-2018 16-5-2018 16-5-2018

Please cite this article as: Kavun VYa, Davidovich RL, Udovenko AA, Polyantsev MM, Logvinova VB, Synthesis, crystal structure, and 19 F, 1 H NMR investigation of the first compound of indium(III) with an amino acid, Journal of Fluorine Chemistry (2018), https://doi.org/10.1016/j.jfluchem.2018.05.006 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.

Synthesis, crystal structure, and 19F, 1H NMR investigation of the first compound of indium(III) with an amino acid V.Ya. Kavun, R.L. Davidovich, A.A. Udovenko, M.M. Polyantsev, V.B. Logvinova Institute of Chemistry FEBRAS, 159, Pr. 100-letiya Vladivostoka, Vladivostok, 690022, Russia

E-mail of the corresponding author: [email protected]

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Graphical abstract

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Highlights

The first complex of In(III) with an amino acid (C2H6NO2)3[InF6] was synthesized.

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The structure and ion mobility in (GlyH)3[InF6] have been studied by X-ray diffraction

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

and NMR spectroscopy.

The diffusion of fluoride and proton ions in (GlyH)3[InF6] is observed above 335 K.

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

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 Analysis of NMR data made it possible to identify types of ion mobility at 150–370 K.

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Abstract. The first compound of indium(III) with an amino acid – triglycinium hexafluoridoindate(III), (C2H6NO2)3[InF6] – was synthesized and investigated by X-ray, and 19F, 1 H NMR methods. The structure of (C2H6NO2)3[InF6] is formed by slightly distorted octahedral complex [InF6]3– anions and protonated glycinium cations (C2H6NO2)+, which are linked by hydrogen bonds into a three-dimensional framework. The character of ionic motions in fluoride and proton sublattices upon temperature variation has been examined, and their types and temperature ranges, within which they are realized, have been determined. Keywords: glycinium cation, hexafluoridoindate(III), structure, diffusion ions, 19F and 1H NMR spectra. 1.

Introduction 1

Amino acids can exist in three forms: neutral zwitterion molecules, protonated cations, or deprotonated anions. Glycine is the simplest amino acid. There are numerous known glycine compounds containing as zwitterion molecules (C2H5NO2) as protonated glycinium cations ((C2H6NO2)+,

{(+NH3–CH2–COOH)})

marked as Gly and GlyH+, respectively [1]. To

continue

our

systematic

investigations concerning the chemistry and

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structure of the complex III-V group metal fluorides aiming to reveal new structural

Fig. 1. The structure of the compound I.

motifs and to establish the regularities in formation of these compounds, a number of new

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fluoride complexes with various amino acids containing neutral zwitterion molecules as well as protonated cations was synthesized and studied by the XRD method. Earlier we synthesized and structurally studied a series of fluoride complexes of metals with glycine, in particular, GlySbF3 [2], containing a neutral zwitterion molecule and fluoride complexes (GlyH)SbF4 [2],

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(GlyH)2ZrF6 [3] (GlyH)ZrF5·2H2O [3, 4], and (GlyH)2NbOF5 [5] with protonated glycinium

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cations. Recently, an article on the synthesis and investigation of the first aluminum compound

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with an amino acid, triglycinium hexafluoriodoaluminate was published [6]. There is no available information on compounds of indium(III) with amino acids in the literature. We the

first

indium(III)

compound

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synthesized

with

an

amino

acid

–

triglycinium

hexafluoridoindate(III) (GlyH)3[InF6] (I) – and investigated it by X-ray diffraction analysis, and F, 1H NMR spectroscopy. The composition of the synthesized compound (GlyH)3[InF6] was

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determined by X-ray diffraction analysis.

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2. Results and Discussion 2.1. X-ray data

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The compound I crystallizes in a trigonal symmetry, space group R3, Z = 6. The crystal

structure of (C2H6NO2)3[InF6] is composed of isolated slightly distorted octahedral complex anions [InF6]3– and protonated glycinium cations (C2H6NO2)+ (Fig. 1). In the complex anion

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[InF6]3–, the In–F(2) bond length is equal to 2.042(1) Å, while that of the In–F(1) bond – to 2.068(1) Å, Table 1. The found lengths of In–F bonds in the structure of I are in the range 2.046– 2.095 Å revealed in structures of complex fluorides containing isolated octahedral complex anions [InF6]3– [7]. Distortion of the octahedral complex anion [InF6]3– in the structure of I in comparison with a regular octahedron is characterized with the values of F–In–F cis-angles equal to 87.96(4) and 92.04(5)o and a deviation from 180 of the values of F–In–F trans-angles equal to 175.64(4)o, Table 1. 2

Table 1 Selected bonds (d, Å) and angles ( in the structure (C2H6NO2)3[InF6] d 2.068(1) 2.042(1)

Bond C(1)–O(1) C(1)–O(2) Angle

d 1.210(1) 1.305(1)

Bond C(1)–C(2) C(2)–N Angle

d 1.499(2) 1.472(1)

F(1)InF(1A)

87.68(4)

O(1)C(1)O(2)

124.5(1)

NC(2)C(3)

110.1(1)

F(1)InF(2)

92.31(5)

O(1)C(1)C(2)

113.0(1)

C(2)C(3)C(4)

112.4(1)

F(1)InF(2A)

87.96(4)

O(2)C(1)C(2)

122.5(1)

C(2)C(3)C(5)

111.6(1)

F(2)InF(2A)

92.06(4)

C(1)C(2)C(3)

114.0(1)

C(4)C(3)C(5)

F(1A)InF(2A)

175.63(5)

C(1)C(2)N

106.9(1)

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



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Bond In–F(1) In–F(2) Angle

111.5(2)

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In glycinium cations (+NH3–CH2–COOH) in the structure of I, both amino and carboxylate groups are protonated. In the compound COOH groups, the C(1)–O(1) and C(1)–O(2) bond lengths are equal to 1.210(1) Å and 1.305(1) Å, respectively, indicating that the carboxylate group is protonated. The С(1)–С(2) (1.499(1) Å) and С(2)–N(1) (1.472(1) Å) distances in the

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GlyH+ cation are characteristic of such bonds in amino acid cations [1].

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In the structure, COOH and NH3+ groups of the cation form a branched system of

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hydrogen bonds O–H···F, N–H···F, and N–H···O, which link cations and anions into a three-

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dimensional framework. 2.2 NMR data

Temperature dependencies of the widths of

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F and 1Н NMR spectra of (C2H6NO2)3[InF6]

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and their transformation upon temperature variations are shown in Figs. 2 and 3. The presence of a plateau on the temperature dependence ΔH½(F) = f(T) in the range 150–250 K (Fig. 2) and the

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respective observed shapes of 19F NMR spectra (Fig. 3) indicate to the absence of ionic motions

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with frequencies above 104 Hz in the fluoride sublattice (“rigid lattice” in NMR terms [8, 9]). Above 250 K, one observes narrowing of NMR spectra related to the emergence of local motions in the fluoride sublattice, whose estimated activation energy values (Ea) are ≈0.42 eV. Taking into account the compound structure, different reorientations of octahedral InF6 units will constitute the most probable type of these motions.

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Note that reorientations of octahedral units comprise a

Fig. 2. Temperature dependencies of halfwidths of 19F, 1Н lines in NMR spectra of (C2H6NO2)3[InF6].

typical motion for compounds containing such ions [9–

12]. Transition of octahedral units from the rigid lattice to reorientations in (C2H6NO2)3[InF6] dependence of ΔH½ (Fig. 2). In the temperature range 320–335 K, isotropic reorientations of InF6 octahedra constitute a predominant type of ionic mobility in the 19

F NMR

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Above 345 K, there starts a transformation of

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compound (S2(F) ≈10 G2 at 335 K, CS ≈3.5 ppm).

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completes at 310 K, as seen from the temperature

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spectra of (C2H6NO2)3[InF6] related to the emergence of

“narrow” components with CS of 36 and 4 ppm, width of

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2.5–3 kHz, and total area not larger than 5.5 % (T = 360 K). At 370 K, the NMR spectrum is simulated by three

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components (Fig. 4), whereas narrow lines occupy not larger than 21 % of total area of the

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F NMR spectrum.

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Upon the sample cooling (370→300 K), the NMR

Fig. 3. Evolution of 19F and 1H NMR spectra shape versus temperature for (C2H6NO2)3[InF6].

spectrum parameters correspond virtually completely to those of the initial compound spectrum

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(Fig. 3), which indicates to preservation of the composition and structure of the compound under

Fig. 4. Deconvolution of the 19F NMR spectrum for the (C2H6NO2)3[InF6].

study. An appearance of narrow lines of widths less than 3 kHz in NMR spectra is, as a rule, related to the existence of diffusion processes in the sample [8–10]. Diffusion of fluoride ions in compounds with octahedral anions was observed for K2TiF6 [13], NH4TiF5 [14], and M2Zr(Hf)F6 (M = Rb, Cs) [15], as well as in [11]. The presence of two

narrow lines of widths of ≈3 and 2.5 kHz (CS = 36 and 4 ppm, Fig. 4) in the 19F NMR spectrum of the compound under study at 370 K indicates to diffusion in its fluoride sublattice. The narrow component in the NMR spectrum with CS = 4 ppm is twofold more intensive than that with CS = 4

36 ppm and, probably, can be assigned to diffusing fluoride ions of the octahedral [InF6]3– anion. The main component of a width of ~17.5 kHz (CS = 2 ppm) is related to fluoride ions of reorienting InF6 octahedra. Assignment of the third narrow component with CS = 36 ppm (6.5 % of total spectrum area) is complicated. Two models below can be suggested for possible mechanisms of diffusion in the fluoride sublattice of (C2H6NO2)3[InF6] [11, 15]: diffusion of the complex InF63 anion as a whole or as consecutive diffusion leaps of individual F ions from one complex ion to another, which has a

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vacancy in the fluoride ion site in the octahedron. In the latter case, the ionic transport can be realized through two motions types occurring sequentially: fluoride ions leaps from one octahedron to another with subsequent reorientation rotation of this polyhedron, after which the

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fluoride ion can make a new leap to the consecutive InF6 octahedron, etc.

Temperature dependencies of the widths of 1H NMR spectra of (C2H6NO2)3[InF6] and their transformation upon temperature variations are shown in Figs. 2, 3. The observed shapes of 1Н

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NMR spectra of (C2H6NO2)3[InF6] differ from those of the molecular glycine in the Li(NH3CH2COO)(NO3) compound, whose two-component shape is determined, under the same Н NMR spectra of the compound under study acquire the shape similar to the triangular one,

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conditions, by superposition of signals from NH3 and methylene groups [16]. Above 170 K, the which preserves until 370 K (Fig. 5). Simulation of 1Н NMR spectra of (C2H6NO2)3[InF6]

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demonstrated that the spectrum “triangular” shape resulted from superposition of at least two

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Fig.5. Simulation of the 1Н NMR spectra of the (C2H6NO2)3[InF6] compound at some temperatures. resonance lines from proton-containing groups of glycinium characterized with different widths, integral intensities, and chemical shifts. A possible reason of such spectrum transformation can

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consist in the increase of the frequency of reorientations of NH3 groups upon the temperature increase (170→200 K), which results in the decrease of dipole–dipole interactions, general narrowing of the NMR spectrum, and, finally, in the emergence of the possibility of registration of components assigned to different proton-containing groups of the glycine cation. A new transformation of 1H NMR spectra of (C2H6NO2)3[InF6] starts above 335 K (Fig. 3) and is related to the emergence of a narrow component (ΔH½(H) ≈3 kHz) with CS = –9 ppm in the spectra, whose intensity increases along with the temperature increase at the expense of the 5

decrease of the broad component area. Here, the NMR spectrum preserves a triangular shape and consists (at 370 K) of two narrow and one broad components (Fig. 5). One of the narrow components with CS = ‒14 ppm and the area <3.5 %, probably, can be assigned to adsorbed water molecules. The width of the second narrow component (ΔH½(H) ≤ 2 kHz, area 16.5 %) with CS = ‒9 ppm indicates to the emergence of diffusion in the compound proton system. Possibly, one of the diffusion routes comprises the transition between different forms of glycinium cations, while another one – the proton migration over the lattice. According to the 1H

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NMR data, diffusion in the proton sublattice of the Li(NH3CH2COO)(NO3) compound is observed above 380 K with participation of one of the glycine molecule protons [16]. Probably, a broad component in the spectrum can be assigned to hydrogen atoms of proton-containing

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glycinium groups, between which a fast proton exchange takes place at high temperatures: as a result, one registers a single broad unstructured line in the 1H NMR spectrum at 370 K. Upon the sample cooling (370 → 300 K), the shape of the 1H NMR spectrum returns to the initial shape (Fig. 3). Above 380 K, the compound I transforms into the X-ray amorphous phase, according to

amorphous

phase

as

a

result

phase

transition

in

a

new

compound

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(C2H5NO2)[SbF3]2·above 440 K.

of

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X-ray

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the powder X-ray data. Note that we observed similar transformation of the crystal phase to the

3. Conclusions

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The crystal structure of the first synthesized compound of indium(III) with an amino acid (triglycinium hexafluoridoindate(III)) was determined and investigated by

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F,

1

H NMR

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spectroscopy. According to the 19F NMR data, isotropic reorientations of octahedral InF6 groups constitute a predominant type of ionic mobility in the fluoride sublattice of (C2H6NO2)3[InF6] in

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the temperature range 250–370 K. The emergence of a partial diffusion of fluorine ions and protons in both sublattices of the compound I was observed. The transition of the crystalline

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phase to the X-ray amorphous phase occurs above 380 K. 4. Experimental 4.1. Synthesis

The (GlyH)3[InF6] compound was synthesized by the preparative method through

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interaction of InF3·3H2O and glycine in an aqueous solution of HF at the components molar ratio of 1:3. The obtained solutions were left for isothermal crystallization at room temperature. The formed crystalline precipitates were separated from the stock solution by filtration in vacuum, washed with a small amount of cooled water, and dried in air. 4.2. NMR study The

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F and 1H NMR spectra of the (C2H6NO2)3[InF6] sample were recorded using a

Bruker AVANCE-300 spectrometer at Larmor frequencies L = 282.404 MHz (for 6

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F nuclei)

and L = 300.13 MHz (for 1Н nuclei) at temperatures from 150 to 370 K [17]. The temperature adjustment accuracy was 2 K. Calculations of the RMS width of NMR spectra (or the second moment S2, in G2) were performed using an original code by formulas given in [18, 19]. The full width at half maximum of an integral line ΔH½ (in kHz) and the chemical shift (CS) (in ppm vs. C6F6) were estimated from the spectra with an accuracy of 2 % and 1 ppm, respectively. Chemical shifts of C6F6 are –589 ppm relatively to gaseous F2, (δ(F2) = 0 ppm) and –167 ppm relatively to CFCl3 [19]. The chemical shift in 1H NMR spectra was measured relatively to

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tetramethylsilane (TMS). Simulations of experimental 19F NMR spectra were carried out by the original computer program, which allows performing the spectrum decomposition into components and determining their positions, integrated intensity (in % to the total spectrum

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area), width, second moment, and type of the function that describes the shape of the resonance line (Gaussian, Lorentzian etc.). The program fitting of the experimental spectrum was performed by minimization of the sum of squared deviations between experimental and calculated spectral points. The modified Newton's method was used for the minimization.

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Squares of the narrow and broad NMR components corresponding to ‘mobile’ (correlation

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frequency νc > 104 Hz, [9, 18]) and ‘immobile’ (νc ≤ 104 Hz) F− ions were measured with an

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error below 5 %. The spectrum simulation accuracy was from 1 to 5 %. The activation energy

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(ENMR) of local (diffusion) motions was estimated by the Waugh–Fedin equation ENMR = 0.0016∙Tc (eV) with an accuracy of 0.03 eV [9]. Tc was taken as the onset temperature (absolute

4.3. X-ray study

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scale) for a decrease of the second moment S2 (or linewidth ΔH½) of 19F NMR spectra.

Powder X-ray diffraction data (XRD) were recorded using a Bruker D8 ADVANCE

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diffractometer on CuKα radiation.

The X-ray structure measurements were performed with a single crystal of a lamellar shape

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using a Bruker KAPPA APEX II diffractometer (MoK-radiation, graphite monochromator). The experimental data were collected through ω-scanning at an increment of 0.3 in the area of hemisphere of the reciprocal space with an exposure time of 20 s per frame at a distance between the crystal and the detector of 45 mm. Absorption was taken into account empirically using the

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SADABS program [20]. The structure of I was determined by a direct method and refined by the least-square method in the anisotropic approximation of non-hydrogen atoms. The positions of hydrogen atoms of the glycinium cation were calculated geometrically and included into refinement in the “riding” model. Collection and editing of the data and refinement of the unit cell parameters were carried out using the SMART and SAINT Plus programs [20]. All the calculations on determination and 7

refinement of the structure were carried out using the SHELXTL/PC programs [21]. Main crystallographic data and details of refinement of the crystal structure of I are shown in Table 2. Table 2 Crystallographic data, experimental parameters, and structural refinements Compound Molecular weight Temperature, K Wavelength, Å Symmetry Space group

(C2H6NO2)3InF6 457.05

296(2) МоК (0.71073)

Trigonal

a, Å c, Å 

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V, Å3 Z cal, g/cm3 , mm–1

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R3 10.9852(2) 21.6031(5) 120 2257.7(1) 6 2.017 1.667

F(000)

2.34-43.72 -20
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Crystal shape Data collection area in ,deg. Reflection index ranges

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1356

Plate (0.20×0.20×0.12) mm

1826388

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Measured reflections number Independent reflections Reflections with I> 2(I) Refinement variables GooF R-factors on F2> 2(F2) R-factors on all reflections Residual electron density (min/max), e/Å3 CCDC No.

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