Synthesis, Crystal Structure, and Spectroscopic Characterization Supported by DFT Calculations of Organoarsenic Compound

Journal of Molecular Structure 1144 (2017) 25e32

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Journal of Molecular Structure

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Synthesis, crystal structure, and spectroscopic characterization supported by DFT calculations of organoarsenic compound

* Nasreddine Ennaceur, Ph.D a, b, , Rokaya Henchiri a, b, Boutheina Jalel a, b, Marie Cordier c, Isabelle Ledoux-Rak b, Elimame Elaloui a a Laboratory of Materials, Energy and Environment UR 14/ES 26 University of Gafsa, 2100 Gafsa, Tunisia b Laboratory of Quantum and Molecular Photonics, Institut d'Alembert, Ecole Normale Superieure de Cachan, 94230 Cachan, France c Molecular Chemistry Laboratory, UMR 9168, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex, France article info abstract

Article history: A new semi-organic hydrogen bonding complex salt of 2-ammonium phenylarsonic acid and nitric acid Received 21 March 2017 has been synthesized, thus successfully growing good quality single crystals by means of slow solvent Received in revised form evaporation technique at ambient temperature. The 1H and 13C NMR spectra were recorded to establish 1 May 2017 the molecular structure. The conducted single crystal XRD analysis has shown that the title salt is Accepted 3 May 2017 crystalized in orthorhombic crystal system with centrosymmetric Pbcm space group. The structure Available online 3 May 2017 ﬁ þ consists of in nite parallel two-dimensional planes built of (C6H6NH3AsO3) organic cation and NO3 inorganic anions connected by hydrogen bonds and p-p interactions giving birth a three-dimensional Keywords: Crystal growth network. The performed TG/DSC thermal analysis has established the thermal stability of the crystal. X-ray diffraction The optimized structural parameters and vibrational frequencies (the experimental and theoretical DFT calculations vibrational frequencies) were assigned and compared by the Density Functional Theory (DFT) using the Optimized geometry Gaussian method (DFT/B3LYP). Good consistency results were found between the calculated and the Delocalized p-electron experimental crystal structure and FT-IR spectra. Infrared spectroscopy © 2017 Elsevier B.V. All rights reserved. Thermal behavior

1. Introduction coccidial intestinal parasites [6e8]. Furthermore, arsanilic acid and its analogs react with several metal ions at different pH values to Aminophenylarsonic acid (ortho and para) was known as a form precipitates, due to the fact that the arsenate group AsO(OH)2 biomedical molecule for example an antihelminth in veterinary acts as a bidentate ligand. This allows the preparation of polymers applications [1]. Besides, some are still used against trypanosomal with good chelating properties [9e13]. Besides, during the last infection despite their toxicity [2] and more commonly as a pre- decade, the search for new efficient nonlinear optical (NLO) ma- viously employed antisyphilitic drug [3], when used as the hy- terials has led to a large investigation for suitable organic, polymers drated sodium salt, under a variety of common names, namely and hybrid compounds [14e17] thanks to their high nonlinear atoxyl. These structures are among only a small number of exam- optical properties compared to inorganic NLO materials. Such in- ples in the crystallographic literature involving this acid in any terest has been driven by a number of potential applications, as form, which include the complexes with some metals like silver, second harmonic generation (SHG), electrooptic modulation, fre- zinc, cadmium, lead and the sodium salt of a hybrid organic- quency mixing and optical parameter oscillation, among others. inorganic polyoxovanadate cluster complex formed with arsani- However, the majority of organic materials crystallized in late anions [4,5]. centrosymmetric space groups and consequently they fail to Moreover, arsanilic acid is an aromatic organoarsenic compound exhibit SHG. To generate SHG from organic structures, different that has been widely used as a feed additive in the poultry and pig techniques have been used to remove the centre of symmetry along farms to improve the growth rate, feed efficiency, and control with the internal charge transfer within conjugated molecules to achieve efficient optical nonlinear effects. The hydrogen-bonding character in organic and inorganic materials can also introduce * Corresponding author. Laboratory of Materials, Energy and Environment UR 14/ noncentrosymmetric crystal structure [18,19]. It is this insufficiency ES 26 University of Gafsa, 2100 Gafsa, Tunisia. found in the literature that encouraged us to make this combined E-mail address: [email protected] (N. Ennaceur). http://dx.doi.org/10.1016/j.molstruc.2017.05.007 0022-2860/© 2017 Elsevier B.V. All rights reserved. 26 N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32 theoretical and experimental study, as it is a powerful tool for the employing a Perkin Elmer FT-IR spectrometer in the range confirmation of the expected crystal obtaining and the description 4000e400 cm 1. The TGA and DSC studies were carried out on a of crystalline materials (nitrate 2-aminophenylarsonate mono- PERKIN ELMER DIAMOND instrument with a heating rate of 10 C/ hydrate abbreviated NAPM). The spectroscopic analysis can also min in the temperature range from 20 to 600 C in nitrogen at- provide more precise information about the strong relation be- mosphere. The UVevis spectrum of the molecule was also recorded tween molecular structure and charge transfer. The present by the UVeVis spectrophotometer in the wavelength region research work deals with the single X-ray diffraction (XRD) study, 200e800 nm using deionized water as a solvent. the detailed vibrational spectral studies assisted by density functional theory (DFT) calculations, nuclear magnetic resonance 3. Results and discussion spectral studies, ultravioletevisible (UVeVis) spectroscopic studies and thermal analysis TGeDSC of the NAPM. 3.1. EDAX analysis

2. Experimental procedure The percentage composition of the elements present in NAPM was confirmed by using JEOL JSM-6380LA analytical scanning 2.1. Materials synthesis, crystal growth electron microscope (SEM) system. Fig. 2 shows the resulting spectrum over a certain area. The typical peaks in the spectrum The starting material of 2-aminophenylarsonic acid and nitric proved the presence of various elements in the grown crystal. acid was taken in 1:1 stoichiometric ratio to synthesize nitrate 2- aminophenylarsonate monohydrate. The calculated amount of the 3.2. Single crystal X - ray diffraction study 2-aminophenylarsonic acid was first dissolved in deionized water. The nitric acid was then slowly added to the solution by stirring. The single crystal of NAPM compound was mounted on a Kapton The prepared solution was allowed to dry at room temperature and loop using a Paratone N oil. An APEX II CCD BRUKER detector and a the salt was obtained by slow evaporation technique. The purity of graphite Mo-Ka monochromator was used to obtain the data. One 3 the synthesized salt was successfully improved by recrystallization. single crystal of the size of 0.26 0.20 0.080 mm was used for After 20 days of growth, a transparent single crystal of dimension the present study. All measurements were carried out at 150 K, a 10 9 4 mm was obtained by the slow evaporation technique. refinement method was used for solving the structure, whose The photograph of the as-grown crystal of NAPM is shown in Fig. 1. resolution was accomplished using the SHELXT-2014 [20] program, The crystal had good compositional stability and showed no and the refinement was done with the SHELXL-2014 program [21]. degradation when stored in the open air for several months. NAPM The solution structure and refinement were achieved with was synthesized according to the following chemical reaction. the PLATON software. During the refinement steps, all atoms except hydrogens were refined anisotropically. The position of the H O C H NH AsO þ HNO 2!ðC H AsNO ÞðNO Þ$H O hydrogen was determined using residual electronic densities, 6 6 2 3 3 6 9 3 3 2 which are calculated by a Fourier difference. The single crystal diffraction studies were carried out to find the crystal structure and the cell parameters of the grown material. The single crystal XRD 2.2. Characterization study has proven that the crystal belongs to orthorombic system, and the space group has been found as Pbcm with the lattice pa- To confirm the molecular structure of NAPM crystal, the per- rameters: a ¼ 11.6562(3) Å, b ¼ 12.1577(3) Å, c ¼ 7.4854(2) Å and 3 centage composition of the elements present in NAPM was V ¼ 1060.78(5) Å . The crystal data and the structure refinement for confirmed by using JEOL JSM-6380LA analytical scanning electron NAPM material is given in Table 1. Isotropic or equivalent isotropic microscope (SEM) system. The NMR study was recorded employing displacement parameters and fractional atomic coordinates are a Bruker 400 MHz spectrometer in deuterated solvent. The crystal summarized in Table 2. For further details of the structure deter- structure was determined from the single-crystal X-ray diffraction mination, they are available from the Cambridge crystallographic data obtained with an APEX CCD area-detector diffractometer. FT-IR data centre CCDC 1476254. spectrum was recorded using potassium bromide pellet method 3.2.1. Description of the structure The structural determination of NAPM compound has established the structural model in which the asymmetric unit (Fig. 3) þ consists of a protonated organic cation (C6H6NH3AsO3) , one inorganic anions NO3 and H2O molecule. These entities are linked by hydrogen bonds and p-p interactions involving a crystal structure in a three-dimensional network. Fig. 4 shows the projection of the crystal structure of NAPM in the (a, b) plane. Anionic group constituted by nitrate developed in wires along the [100] direction þ alternately with the cationic group (C6H6NH3AsO3) and water molecule H2O. The latter are inserted between the organic (cationic) and mineral (anionic) groups. These positions provide stability and cohesion to the structure.

3.2.2. The cationic group O-Arsanilic acid is an organoarsenic compound, also called 2- aminophenylarsonic acid. It is a planar molecule having a conjugated ring system and its protonation was performed on the N1 nitrogen atom. On this molecule, the arsanilic acid group AsO3H2 is Fig. 1. Photograph of as-grown NAPM crystal. grafted. The dihedral angle observed between the amine group and N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32 27

Fig. 2. EDAX spectrum of NAPM.

Table 1 Crystal data, summary of intensity data collection and structure reﬁnement.

Crystal data . Chemical formula (C6H9AsNO3)(NO3) H2O Formula weight (g mol 1) 298.09 Crystal system Orthorombic Space group P bcm a(Ǻ) 11.6562(3) b(Ǻ) 12.1577(3) c(Ǻ) 7.4854(2) F(000) 600 V(Ǻ3) 1060.78(5) Z 4 Crystal size (mm3) 0.260 0.200 0.080 mm Color Colorless/plate Intensity data collection Diffractometer Kappa Apex II Wavelength l (Ka) ¼ 0.71069 Å Absorption corrections Multi-scan Temperature (K) 150 q range for data collection () 1.9 q 27.472 Range of h, k, l 15 h 15; 15 k 15; 9 l 9 21 l 19 Reflections measured 17901 Independent reflections [I > 2s (I)] 1307 Structure refinement Computer programs ShelxT et Shelxl Refinement based of F2 Electron density residuals (e. Ǻ 3) 0.463< Dr <0.684 Goodness-of-fitonF2 1.083 Flack parameter 0.00 (1)

wR2 (%) 6.98 R1 (%) 2.78 Cambridge Crystallographic Data Centre (CSD) CCDC Number:1476254

the benzene of the organic cation is 180, which confirms the good axis ¼ 0 and regularly with c ¼ ¼ and ¾ (Fig. 5). The detailed ge- flatness of the organic cation. The values of the average distances of ometry of the nitrate entities shows that the N2eO3 and N2eO3b CeC and CeH are equal to 1.385 and 0.95 Å, respectively; and the [1.233(2) Å] bond lengths are meaningfully shorter than the N2eO4 CeCeC and NeCeC angle are around to 120 and 119.8, respec- [1.290(4) Å], which is in agreement with the relatively strong tively. All these interatomic distances and angles of the cationic interaction involving the O4 atom with the AsO3H2 molecule entity are comparable to those of the 1-Aminobenzene cation [22] O4eH4/O1 [2.668 (1) Å]. compounds except the CeC distances, which are shorter, about 0.7%, due to the attractive electrostatic interactions of the nitrate 3.3. Geometry optimization ! anion. The organic group is developed in zigzag in a direction at b ¼ ¼ and ¾, forming layers that develop in parallel with the [010] The geometry optimization of NAPM was carried out from the X- direction in c ¼ ¼ and ¾ (Fig. 5). ray experimental atomic position crystallographic information file (CIF). All other computations engaging density functional theory 3.2.3. The anionic group (DFT) were conducted by the resultant optimized structural pa- In the nitrate anion NO3 , alternating short and long distances is rameters at B3LYP/6-31G(d) [24] without any constraint to the strongly linked to the delocalized electron leading to a mesomeric potential energy surface. As shown in Table 3, the optimized effect [23]. It is observed that the nitrate anions are developed structural parameters (bond lengths, bond angles) of NAPM have along the b-axis in two altered levels, in zigzag whose mean a- been compared with those obtained experimentally. The optimized 28 N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32

Table 2 Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2).

a xyzUiso /Ueq As1 0.23018 (3) 0.41434 (2) 0.7500 0.01563 (12) O1 0.3662 (2) 0.37685 (18) 0.7500 0.0204 (5) O2 0.14973 (14) 0.36096 (13) 0.5807 (2) 0.0243 (4) H2 0.1765 0.3805 0.4845 0.037a N1 0.4186 (2) 0.6087 (2) 0.7500 0.0175 (5) H1A 0.424 (3) 0.533 (3) 0.7500 0.021a H1B 0.450 (2) 0.635 (2) 0.849 (3) 0.021a C1 0.2089 (3) 0.5691 (2) 0.7500 0.0179 (6) C2 0.2985 (3) 0.6443 (2) 0.7500 0.0160 (6) C3 0.2763 (3) 0.7564 (3) 0.7500 0.0246 (7) H3 0.3377 0.8078 0.7500 0.030a C4 0.1635 (3) 0.7926 (3) 0.7500 0.0345 (9) H4 0.1477 0.8693 0.7500 0.041a C5 0.0744 (3) 0.7187 (3) 0.7500 0.0357 (9) H5 0.0025 0.7444 0.7500 0.043a C6 0.0965 (3) 0.6067 (3) 0.7500 0.0273 (7) H6 0.0347 0.5557 0.7500 0.033a O3 0.35466 (15) 0.00711 (13) 0.6055 (2) 0.0267 (4) O4 0.2208 (2) 0.0936 (2) 0.7500 0.0367 (7) N2 0.3127 (2) 0.0345 (2) 0.7500 0.0212 (5) O5 0.47354 (19) 0.2500 0.0000 0.0209 (5) H5A 0.432 (3) 0.215 (3) 0.067 (4) 0.050 (10)a Fig. 4. The projection of the crystal structure of NAPM in the (a, b) plane.

a H atoms were reﬁned isotropically.

Table 2: Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

Fig. 3. The asymmetric unit of the NAPM compound.

and experimental structures of NAPM were compared by super- sample in deuterated water (D2O). The singlet at 4.69 ppm is due to imposing them employing a least squares algorithm that minimizes the D2O solvent. The multiplet chemical shifts at [7.21e7.52] ppm the distances of the corresponding non-hydrogen atoms. The are attributed to the protons of aromatic ring, OH group and NH3 agreement between the experimental and optimized crystal group of arsanilic acid. The 13C spectrum of NAPM proves the structure is quite good. The calculated bond lengths of CeCin presence of 4 types of carbon. The 13C chemical shift appearing at phenyl rings fall in the range from 1.386 to 1.388 Å, which are in 145 ppm confirms the presence of CeN functional group in arsanilic good agreement with the experimental results 1.385e1.388 Å. Due acid and the presence of aromatic carbon chemical shift is at 135, to a larger atomic radius of arsenic, the AS-C aromatic bond pos- 130, 122 and 120 ppm (CH). The conformation of another type of sesses higher value (1.898 Å) as compared to other bond length carbon appears at 118 ppm (CeAs). Thus, the characteristic func- values. The average bond distances of AS-O (1.649e1.704 Å) and tional groups of NAPM compound were confirmed through the NeC aromatic (1.465 Å) agree well with the data reported in the proton and carbon NMR analyses. literature. The values of AS-O and NeC aromatic for ammonium 4- aminophenylarsonate monohydrate [3] are (1.672e1.746 Å) and 3.5. Thermal analysis 1.396 Å and (1.670e1.745 Å) and 1.391 Å for catena-poly[[(4- k m . aminophenylarsonato- O)diaquasodium]- -aqua] [3]. During the decomposition of NAPM (C6H9AsNO3)(NO3) H2O,TGA curve revealed that there are two-steps weight losses (Fig. 6). 3.4. NMR spectral studies The first decomposition, from 93 to 120 C, is due to the loss of the guest water molecule (experimental weight loss: 5.7% and 1H NMR and 13C NMR spectrum was recorded by dissolving the theoretical weight loss: 6%) and leading to the anhydrous N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32 29

Fig. 6. TGA and DSC thermograms of the NAPM crystal.

lambda 35 spectrometer, in the range of 200e800 nm. The measurements were performed in 1 cm (quartz) cell using a solution of low concentration (c ¼ 10 5 mol l 1). Fig. 7 shows the optical absorption spectrum of the NAPM crystal. The crystal is totally Fig. 5. The projection of the crystal structure of NAPM in the (a, c) plane.

Table 3 Comparison between the observed and calculated bond lengths of NAPM.

Within the mineral moieties

Parameters Experimental Theoretical Parameters Experimental Theoretical

N2eO3 1.233 (2) 1.2329 As1eO1 1.649 (2) 1.6497 N2eO4 1.290 (4) 1.2899 As1eO2i 1.7046 (15) 1.7048 N2eO3i 1.233 (2) 1.2328 As1eO2 1.7046 (15) 1.7048 O3eN2eO3i 122.6 (3) 122.64 O1eAs1eO2i 115.06 (7) 115.051 O3eN2eO4 118.68 (14) 118.68 O1eAs1eO2 115.06 (7) 115.053 O3idN2dO4 118.68 (14) 118.67 O2idAs1dO2 96.02 (11) 96.032 O3eN2eO3i 122.6 (3) 122.64 O1eAs1eC1 113.54 (12) 113.548 O2idAs1dC1 107.80 (8) 107.790 O2eAs1eC1 107.80 (8) 107.791 N1eC2 1.465 (4) 1.4652 C1eC2eC3 120.4 (3) 120.448 C1eC2 1.388 (4) 1.3880 C1eC2eN1 121.7 (3) 121.620 C1eC6 1.388 (5) 1.3876 C2eC1eC6 119.6 (3) 119.563 C2eC3 1.388 (4) 1.3872 C2eC1eAs1 123.7 (2) 123.691 C3eC4 1.387 (5) 1.3865 C3eC2eN1 117.9 (3) 117.932 C5eC6 1.386 (5) 1.3857 C4eC3eC2 119.3 (3) 119.259 As1eC1 1.898 (3) 1.8977 C4eC5eC6 120.2 (3) 120.150 C5eC4eC3 120.6 (3) 120.630 C5eC6eC1 119.9 (3) 119.950 C6eC1eAs1 116.7 (2) 116.746

Symmetry codes: (i) x, y, zþ3/2.

framework of (C6H9AsNO3)$(NO3). The second stage which starts at transparent in the visible region and as observed in the spectrum, about 147 C and ends above 600 C, is assigned to the destruction the two bands in the higher energy sides (210e230 nm and of the organic entities (experimental loss: 56.5% and theoretical 280e315 nm) arise due to the excitation of electrons of aromatic loss: 56%) and the volatilization of the compound. This phenome- ring systems. For our present compound, the normal higher energy non is accompanied by two sharp exothermic peaks observed on side bands appear at 225 and 275 nm. The peak at 315 nm is the DSC curve at about 147 and 160 C, respectively. assigned to the p-p*transition within AS ¼ O group.

3.6. UVevis analysis 3.7. Vibrational spectral analysis

UVevis studies provide important information about the Molecular vibrations has become more and more important in structure of NAPM because the absorption of UV and visible light both experimental and theoretical communities because it has involves the promotion of the electrons in s and p orbitals from the been well tested as an extremely powerful technique for solving ground state to higher energy states. Within this framework, the many chemical problems, especially in the study of chemical ki- UVevis absorption spectrum was recorded using Perkin-Elmer netics and chemical analysis. 30 N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32

Table 4 Computed vibrational wavenumbers (scaled) FT-IR bands positions (cm 1) with the proposed assignments.

Experimental Theoretical Assignments

3600e3200 sh 3800e3500 y(OH) 3100e2900 sh 3400e3200 y sym(OH/O) þ 3170 vw 3150 y asy(NH3 ) þ 2650 m _ Y sym(NH3 ) 2430 vw 2430 y asy(CH) 1800 w 1750 y sym(CH) þ 1800e1750 w 1750e1730 d (NH3 ) 1580 s 1560 d(OH) 1320 vs 1300 y (AseC) 1250e1200 m 1250e1180 y asy(O3 )þd(CeCeN) 1150e1020 s 1180e1100 d(CeH) 1150e750 s 1180e700 ysym(CeC)þysym(CeN) 1080 m 1100 y (AseC) 900 vs 910 y sym(O3 )þy (As]O) 850 vs 870 y sym(CeNeH) 780 s 780 d (NO ) Fig. 7. UVevisible absorption spectrum NAPM crystal. 3 700 s 700 y (AseO) 670 m 700 r(CH) þ 550 w 500 t (NH3 ) Computational methods based on density functional theory 450 vs 480 t(H2O) (DFT) predict the relatively precise molecular structure and vibrational spectra with moderate computational effort. The calculated parameters by DFT method using B3LYP/6-31G(d) represent good 3.7.1. Phenyl ring vibrations approximations and can be used as a foundation to calculate the NAPM shows the presence of CeH stretching vibrations in the other parameters for the material for clarifying experimental region of 3100e3000 cm 1, which is the characteristic region for phenomena and predicting properties. The molecular structure the ready recognition of CeH stretching vibrations [34]. In this optimization of NAPM, corresponding to energy and vibrational region, the bands are not substantially affected by the position and harmonic frequencies are calculated at DFT/B3LYP level combined the nature of the substituent. The in-plane aromatic CeH bending with standard B3LYP/6-31G(d) basis set to aid the interpretation of vibrations occur in the range of 1100e1000 cm 1. Although these the experimental spectroscopic data. bands are sharp, they have weak to medium intensity. The scaled The experimental and calculated spectra of the title material are vibrations predicted at 1450, 1500 1600 and 800 cm 1 by B3LYP/6- presented in Fig. 8. The detailed assignments of the observed bands 31G(d) method have shown good agreement with the recorded are assembled in Table 4. These assignments have been made by spectral data. The in-plane bending vibrations are mixed with the comparison with the previous theoretical and experimental results ring CeC stretching vibrations. e cited in the literature for similar compounds [25 32] and by the For the title compound, very strong bands are observed at visual inspection of modes animated by using the GaussView 820 cm 1 and at 780 cm 1 in FT-IR spectrum which are supported program [33]. by computational results at 800 and 750 cm 1 [34].

Fig. 8. FTIR spectrum of NAPM crystal. N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32 31

3.7.2. Amino group vibration vibration is observed in the vibrational FT-IR spectrum at 750 cm 1. The asymmetric NH2 stretching will give rise to a band between Such data indicate that for the crystalline state, the selection rules for 3490 and 3400 cm 1, in the case of saturated amines, while the D3h point group do not hold. In fact, when the nitrate ion is in the 1 symmetric stretching will appear between 3310 and 3280 cm lattice, the symmetry of the NO3 ion may be lost due to the hydrogen [35]. The protonation of NH2 group can cause a shift in band po- bond formation and some of the forbidden modes may be excited. sition towards the range 3300e3100 cm 1 for the asymmetric Besides, it is remarkable that the observed bands are changed stretching and 3100e3000 cm 1 for the symmetric stretching as compared to the characteristic wavenumbers of the free nitrate anion þ appeared in amino acid [28]. Furthermore, the NH3 stretching as a result of the charge transfer interaction that takes place within bands are broader and weaker in IR than those arising from the the H-bonded crystal [39]. The spectral assignment of the NO3 uncharged NH2 groups [29]. The observed bands at 3498 and normal modes carried out in this paper agree well with previous 1 1650 cm are assigned to the asymmetric and symmetric vibra- vibrational studies as those of L-asparaginium nitrate [27],L-lysine L- þ tions of NH3 group in NAPM which are supported by computational lysinium dichloride nitrate [28], DL-phenylalaninium nitrate [29], DL- results at. The position of this band clearly indicates the presence of valine nitrate and L-leucine nitrate [30], Lornithine nitrate [31] and b- þ þ NH3 group in the crystal. Thus, the NH3 symmetric stretching alanine b-alaninium nitrate [32]. wavenumbers are overlapping with the vibrations of a CH2 group; the protonation of the NH2 group can be inferred from the FTIR 3.8. Vibrations of water molecule þ spectrum. The observed NH3 stretching wavenumbers are shifted from the computed wavenumbers due to inter- and intramolecular On the free state, the OH stretching of the water molecule appears þ 1 NeH/O hydrogen bonding interactions. The NH3 in the plane and in the 3700e3500 cm region, and the bending mode appears torsion deformation modes appear in the regions 1650-1560 cm 1 around 1595 cm 1 [40]. The symmetric stretching bands of water and 550-500 cm 1, respectively [34]. molecule are observed at 3250 cm 1 (IR) with a strong intensity. The OeH1$$O4 bond distance and bond angle calculated as 2.680A and 3.7.3. CeC, CeH and CeN group 167.9 shows the presence of strong OeH/O hydrogen bond be- The NAPM molecule is a disubstituted aromatic compound with tween the nitrate anion and water molecule. It is found that the OH three CeH moieties, which gives rise to three CeH stretching, vi- stretching mode is considerably lowered by 100 cm 1, thus con- brations. CeH stretching asymmetric frequency occurs in the wave firming the presence of strong OeH/O intermolecular hydrogen number region 2380-2400 cm 1 [36]. The calculated CeH bonding.Thetwistingbandofwaterisfound tooccurat 480cm 1 (IR) stretching frequencies were obtained at 2400, 2430 cm 1. The with a strong intensity. The bending mode is observed at 1530 cm 1 fundamental modes observed at 2380 cm 1 and 1780 cm 1 in FT-IR with a strong intensity. These vibrations modes have proven an spectrum is assigned to the CeH asymmetric and symmetric excellent correlation with our experimental observation. stretching vibrations respectively. The absorption bands corresponding to CeCeN group vibrations have been identified in IR. 4. Conclusion These bands arise from CeN and CeC stretching vibrations and are observed in the wave number range of 1130e750 cm 1 [36]. The The NAPM crystal was grown by the combination of 2- strong IR bands at 780 cm 1and 850 cm 1 are attributed to the CeN aminophenylarsonic acid and the nitric acid at room temperature. symmetric stretching vibrations and rocking CH2 vibrations [37]. This combination has allowed us to obtain a new crystalline phase (C6H9AsNO3)$(NO3)$H2O. The crystal structure was confirmed by 3.7.4. AsO3 group vibrations single crystal XRD in which the asymmetric unit consists of an þ The infrared spectroscopy of NAPM has shown AsO3 stretching organic protonated cation (C6H6NH3AsO3) , one nitrate anion NO3 1 modes at 850 and 700 cm that are supported by computational inorganic anions and H2O molecule. These entities are linked by results at 820 and 700 cm 1, respectively. As]O and AseO hydrogen bonds and p-p interactions involving a crystal structure in stretching vibrations are observed at 1080,900 and 700 cm 1 [4]. a three-dimensional network. Regarding the NMR spectral study, it The CeAs bond is highly polarizable, and hence produces stronger affords the chemical structure of the compound and confirmed the spectral activity. The AseC stretching vibration is expected in the protonation of the NH2 group. Two significant absorptions were 710-685 cm 1 region. In the title molecule, the AseC aromatic observed in the UVeVis region, which arise owing to the excitation stretching vibrations are observed at 700 and 780 cm 1 in the FT-IR of electrons of the aromatic ring systems, hence making the NAPM spectrum. The calculated B3LYP values at 700 and 630 cm 1 exactly suitable for optics applications. The TG/DSC studies have confirmed correlate with the experimental observations as well as literature the thermal stability of the crystal up to 147 C. The vibrational FT-IR data [38]. On the contrary, the AseC stretching mode was found at a spectrum of NAPM was recorded and the vibrational frequencies rather higher frequency of 1320 cm 1. These vibrations are strongly were precisely assigned with the aid of the theoretical calculations coupled with CeC stretching vibrations. at B3LYP/6-31G(d) level. The experimental and theoretical results were found to support each other. The agreement between the 3.7.5. Nitrate anion vibrations observed and calculated vibrational spectra reveals the advantages The nitrate anion has D3h symmetry in their free state, and its of higher basis set for the quantum chemical calculations. The normal modes are n1, n2, n3 and n4. In fact, n1 is the symmetric geometrical parameters of the title compound are in agreement stretching vibration, n2 is the out-of-plane bending vibration, n3 is with the reported XRD results. From the optimized geometry results the doubly degenerate asymmetric stretching vibration and n4 is the and the crystal structure study, we can conclude that the NAPM doubly degenerate in-plane bending vibration, all of which occurring crystal is highly conjugated and delocalized p-electron. In the light at around 1050, 920,1280 and 750 cm 1, respectively [25,26]. The n2, of actual results, NAPM can be used in other applications away from n3 and n4 modes are IR active. In the NAPM, the symmetric stretching its classical use (veterinary applications) such as nonlinear optics vibration n1 is observed in FT-IR spectra at 920 cm 1. The DFT after having integrating chiral molecules in its crystal structure. calculation predicts this mode at 910 cm 1. This excitation of the IR inactive mode n1 is accredited to the local crystalline environment. Conflicts of interest The n3 mode occurs at 1280 cm 1 in the FT-IR spectrum, which is 1 d fi theoretically estimated at 1250 cm .The (NO3 ) in-plane bending The authors declare no competing nancial interest. 32 N. Ennaceur et al. / Journal of Molecular Structure 1144 (2017) 25e32

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