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Structural, vibrational and DSC investigations of the bis-4-benzyl piperidinium tetraoxoselenate monohydrate crystal
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 98 (2012) 222–228
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Structural, vibrational and DSC investigations of the bis-4-benzyl piperidinium tetraoxoselenate monohydrate crystal Y. Kessentini a,⇑, A. Ben Ahmed b, Z. Elaoud a, S.S. Aljuaid c, T. Mhiri a a
Laboratoire de l’Etat Solide, Faculté des Sciences de Sfax, BP. N° 1171, 3000 Sfax, Tunisia Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP. N° 1171, 3000 Sfax, Tunisia c Université de Roi Abdulaziz, Département de Chimie, Faculté des Sciences de Jeddah, Saudi Arabia b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" The 4-BPP crystallizes in the
monoclinic system P21/c. " Two peaks endothermic were shown
at almost 300 and 338 K. " Phase transitions may be interpreted
by a dynamic order disorder mechanism. " The experimental vibrational bands have been discussed and assigned to normal mode.
a r t i c l e
i n f o
Article history: Received 28 March 2012 Received in revised form 27 July 2012 Accepted 30 July 2012 Available online 19 August 2012 Keywords: 4-Benzyl piperidinium X-ray diffraction Vibrational study DFT calculations
a b s t r a c t A new organic–inorganic salt, bis-4-benzyl piperidinium tetraoxoselenate monohydrate has been synthesized and characterized by X-ray diffraction, FT-IR and FT-Raman spectroscopies. The title compound crystallizes in the monoclinic system P21/c at room temperature with the following parameters: a = 8.617(3) Å, b = 27.140(9) Å, c = 10.926(5) Å, b = 96.46(4)° and Z = 4. Its vibrational spectra have been discussed on the basis on quantum chemical density theory (DFT) calculation using B3LYP/6-31G⁄ approach. The role of the intermolecular interaction in this crystal is analyzed. Acidic protons of the selenate group were transferred to the organic cation giving the singly-protonated cation. The ability of ions to form spontaneous three-dimensional structure through O–H O and N–H O hydrogen bond is fully utilized. These hydrogen bonds give notable vibrational effects. Ó 2012 Elsevier B.V. All rights reserved.
Introduction There is still growing interest in the study of crystals containing 4-benzyl piperidinium cation (abbreviated here 4-BPP). Some compounds of the type bis-4-BPP-MX5 (M = Sb, Bi, Cu, Hg and X = Cl, Br) were studied almost 30 years ago to explain the behavior of 4-BPP molecule in the solid state [1–3]. Quite recently, the structure of 4-BPP dihydrogenmonophosphate [4], 4-BPP-1yl-methyl phosphate [5], 4-BPP monohydrogenphosphate pentahydrate [6] and 4-BPP bis-dihydrogenmonophosphate trihydrogenmonophosphate ⇑ Corresponding author. Tel.: +216 22778834. E-mail address: [email protected] (Y. Kessentini). 1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2012.07.133
[7] were published. Some 4-BPP salts crystallize in a noncentrosymmetric space group and exhibit nonlinear optical behavior [8–10]. Few papers with assignments of internal vibrations of 4-BPP molecule were already published. On the other hand, numerous selenate derivatives structural and vibrational studies have been published. The specific acidity of particular derivative allows one to choose appropriate base in crystal engineering of a new materials. In this work, we synthesized a new 4-BPP derivative: bis-4-benzyl piperidinium tetraoxoselenate monohydrate (abbreviated here bis-4-BPPTSe). The crystal is characterized by X-ray diffraction, DSC measurement, FT-IR absorption and FT-Raman scattering. Density functional theory calculation is used in order to perform structure analysis of the studied molecules. In
Y. Kessentini et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 98 (2012) 222–228 Table 1 Comparison between observed and calculated bonds lengths and bonds angles for the bis-4-BPPTSe. Parameters Bond length (Å) C(1)–C(2) C(1)–C(6) C(2)–C(3) C(3)–C(4) C(4)–C(5) C(4)–C(7) C(5)–C(6) C(7)–C(8) C(8)–C(9) C(8)–C(12) C(9)–C(10) C(10)–N(1) N(1)–C(11) C(11)–C(12) C(13)–C(14) C(13)–C(18) C(14)–C(15) C(15)–C(16) C(16)–C(17) C(16)–C(19) C(17)–C(18) C(19)–C(20) C(20)–C(21) C(20)–C(24) C(21)–C(22) C(22)–N(2) N(2)–C(23) C(23)–C(24) Bond angles (°) C(2)–C(1)–C(6) C(1)–C(2)–C(3) C(2)–C(3)–C(4) C(3)–C(4)–C(5) C(3)–C(4)–C(7) C(4)–C(5)–C(6) C(5)–C(6)–C(1) C(5)–C(4)–C(7) C(4)–C(7)–C(8) C(7)–C(8)–C(9) C(7)–C(8)–C(12) C(9)–C(8)–C(12) C(8)–C(9)–C(10) C(9)–C(10)–N(1) C(10)–N(1)–C(11) N(1)–C(11)–C(12) C(11)–C(12)–C(8) C(14)–C(13)–C(18) C(13)–C(14)–C(15) C(14)–C(15)–C(16) C(15)–C(16)–C(17) C(15)–C(16)–C(19) C(17)–C(16)–C(19) C(16)–C(17)–C(18) C(17)–C(18)–C(13) C(16)–C(19)–C(20) C(19)–C(20)–C(21) C(19)–C(20)–C(24) C(21)–C(20)–C(24) C(20)–C(21)–C(22) C(21)–C(22)–N(2) C(22)–N(2)–C(23) N(2)–C(23)–C(24)
Observed 1.359(12) 1.364(13) 1.347(11) 1.404(11) 1.386(10) 1.491(11) 1.367(11) 1.535(10) 1.512(9) 1.538(10) 1.538(8) 1.473(8) 1.475(8) 1.525(9) 1.317(13) 1.364(11) 1.393(12) 1.387(11) 1.372(11) 1.517(11) 1.396(12) 1.513(10) 1.494(11) 1.511(11) 1.522(10) 1.480(8) 1.470(9) 1.495(10) 119.08(1) 120.86(1) 122.49(9) 114.82(8) 123.97(8) 122.55(9) 120.16(9) 121.2(9) 114.58(7) 111.70(6) 107.75(7) 109.72(7) 109.62(6) 110.82(6) 112.07(6) 108.99(6) 111.23(7) 122.68(1) 116.65(1) 123.96(1) 116.9(9) 121.39(9) 121.64(9) 119.22(9) 120.54(9) 114.41(7) 113.27(7) 110.15(7) 110.19(7) 113.81(7) 109.36(6) 113.64(6) 111.09(7)
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Experimental Synthesis
Calculated 1.395 1.396 1.387 1.401 1.401 1.515 1.395 1.546 1.540 1.540 1.530 1.486 1.495 1.526 1.355 1.396 1.396 1.401 1.401 1.515 1.397 1.545 1.520 1.540 1.530 1.484 1.495 1.529 119.23 120.12 121.01 117.82 121.27 121.02 120.13 120.52 114.40 112.38 110.09 109.74 111.85 110.56 113.39 110.52 110.52 120.13 119.52 121.01 118.20 120.44 121.33 120.99 120.12 114.24 112.38 111.13 109.81 111.99 110.06 113.96 109.70
the light of the theoretical calculation, correlation between FT-IR and FT-Raman spectra and computed results help unambiguous identification of vibrational modes and provide deeper insight into the bonding and structural features of the title compound.
The title compound was produced from aqueous solution containing high purity of 4-benzyl piperidine (purity 99%) and selenic acid in the stochiometric ratio 2:1. This mixture was steered and remained clear without any precipitate. After slow evaporation at room temperature, transparency crystals were obtained. X-ray data collection The X-ray data collection was carried out on Enraf-Nonus CAD4 four circle diffractometer using Mo-Ka radiation. A crystal of good quality was selected. The crystal structure was solved by direct method using SHELXS-97. Successive refinements based on F2 lead to a reliability factors of R = 0.0586. Anisotropy thermal displacement parameter refinement was used for all non-hydrogen atoms. Most of the hydrogen atoms attached to carbon and nitrogen were placed at geometrically calculated positions and refined with appropriate riding model. Crystal data and structure solution and refinement details are given in Supplementary Material (Table S1). The bis-4-BPPTSe crystallizes in the monoclinic P21/c system with the following unit cell dimensions: a = 8.617(3) Å; b = 27.140(9) Å; c = 10.926(5) Å and b = 96.46(4)°. Supplementary crystallographic data for this article in CIF format are available as Electronic Supplementary Publication from Cambridge Crystallographic Data Centre (CCDC 826114). Spectroscopic measurements The vibrational measurements were carried out at room temperature. Infrared spectra were taken on a BRUKER IFS-88 spectrometer in the region 4000–400 cm1. Resolution was set up to 2 cm1. Powder Fourier Transform Raman (FT-Raman) spectra were taken with an FRA-106 attachment to the BRUKER IFS-88 spectrometer. Nd3+:YAG air-cooled diode pumped laser of power ca. 200 mW was used as an exciting source. The incident laser excitation is 1064 nm. The scattered light was collected at the angle of 180°in the region 3600–80 cm1 and the resolution was set up to 2 cm1. The polycrystalline powders were achieved by grinding in agate mortar with pestle. Samples were put between KBr wafers. Differential scanning calorimetry Differential scanning calorimetry (DSC) measurements were performed on heating sample from 270 to 400 K on a SETARAM apparatus at a heating rate of 5 K mn1. Computational details The molecular structure of the title compound was fully optimized without any constraint at the Density Functional Theory (DFT) level using the Lee–Yang–Parr correlation functional (B3LYP/6-31G⁄) [11–13] implemented within Gaussian 03 program [14]. In order to take into account the effect of intermolecular interactions on geometrical parameters and vibrational spectroscopy, we have considered the cluster built up from two 4-BPP cations, one selenate anions and one water molecule linked by N–H O and O–H O hydrogen bonds. All the parameters were allowed to relax and all the calculations converged to an optimized geometry which corresponds to an energy minimum as revealed by the lack of imaginary values in the calculated wave numbers. Prior to compare the calculated vibrational wave numbers with the experimental counterparts, the former have been scaled by
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Fig. 1. Atom numbering scheme for bis-4-BPPTSe: (a) the experimental results and (b) the optimized geometry.
Table 2 Geometry of the hydrogen bonds in bis-4-BPPTSe crystal. D–H A
D–H (Å)
H A (Å)
D A (Å)
D–H A (°)
N1–H1A O3(i) N1–H1B O1(j) N2–H2A O1(j) N2–H2B O2(k) O5–HW5A O1(l) O5–HW5B O4(m)
0.90 0.90 0.90 0.90 0.99(2) 1.068(14)
1.82 1.91 1.94 1.80 2.07(4) 1.84(5)
2.704(8) 2.800(9) 2.835(7) 2.690(8) 3.020(8) 2.782(9)
167.2 170.4 176.0 172.3 158(8) 144(7)
Symmetry codes: (i) x + 1, y1/2, z + 1/2; (j) x, y + 3/2, z + 1/2; (k) x + 1, y1/ 2, z + 3/2 (l) x, y, z; (m) x + 1, y + 2, z.
Table 3 Geometry of the Se–O bonds in bis-4-BPPTSe crystal. Se
O(1)
O(2)
O(3)
O(4)
O(1) O(2) O(3) O(4)
1.6407(5) 108.68(2) 108.01(3) 108.06(3)
2.6451(2) 1.6144(4) 108.85(3) 109.38(3)
2.6354(5) 2.6272(3) 1.6157(6) 113.75(3)
2.6301(1) 2.6302(1) 2.7012(3) 1.6090(5)
0.963 scaling factor [15] to correct the evaluated wavenumbers for vibrational anharmonicity and deficiencies inherent to the computational level used. The vibrational modes were assigned on the basis of PED analysis using SQM program [16] and by comparison with the previous theoretical and experimental results reported in the literature for similar compounds. Results and discussions Structure description The title crystal belongs to the P21/c space group of monoclinic system with four formula units in unit cell (Z = 4). It was supposed, that during the complex formation, the acidic protons of the selenate group were transferred to the 4-BPP molecules giving the singly-protonated 4-BPP cation. This statement is in accordance with the crystallographic data. It follows from them that the asymmetric unit comprises ionized selenate anion SeO2 4 , tow singly-proton-
ated 4-BPP cation [C6H5CH2C5H9NH2]+ and water molecule. Selected bonds length and angles together with the calculated ones are presented in Table 1 in accordance with the atom numbering scheme given in Fig. 1a. Optimized geometry of the title compound model is presented in Fig 1b. As seen in Table 1, most of the computed bonds are slightly longer than experimental one. This discrepancies can be explained by the fact that the calculation relates to the isolated molecule where the intermolecular Coulombic interaction with the neighboring molecules are absent, whereas the experimental result corresponds to interacting molecules in the crystal lattice. The maximum difference does not exceed 0.04 Å for the bond lengths and 3.5° for the bond angles. This result shows that the cluster approach is sufficient to the analysis of the spectra in the solid state. The various hydrogen bond parameters are summarized in Table 2. The hydrogen atoms from selenate group was transferred to N(1) and N(2) atoms of 4-BPP rings. The 4-BPP cations do not differ significantly and exhibit the characteristic deformation of the aromatic ring from the ideal hexagonal form. The internal C10–N1–C11 angle (112.07(6)°) protonated at the N atom is significantly greater than other angles within the piperidine ring: C12–C8–C9 (109.72(7)°), C8–C9–C10 (109.62(6)°), C9–C10–N1 (110.82(6)°), N1–C11–C12 (108.99(6)°) and C11–C12–C8 (111.23(7)°). The same situation is observed for C22–N2–C23 angle. It is worthwhile mentioning, that in recently determined structure of 4-BPP dihydrogenmonophosphate pentahydrate [6] and 4-BPP dihydrogenmonophosphate trihydrogenmonophosphate [7] the piperidine ring exhibit similar pattern of the internal C–N–C angle. Bis-4-BPPTSe monohydrate is a new organo-selenate consisting of a structure with strong two dimensional characters based on sheets of SeO2 4 tetrahedron and water molecule fused together via H(OW)–O–Se bonds. The SeO2 4 tetrahedra are associated in pairs through water molecules forming centrosymetric finite clusters [H4Se2O10]4 (for details see Supplementary Material, Fig. S1). These dimers are located at z ¼ 0andz ¼ 12. The 4-BPP cations are joined with the selenate anions through N1– H1A O3, N1–H1B O1, N2–H2B O2 and N2–H2A O1, hydrogen bonds with the lengths ranging from 2.690(8) to 2.835(7) Å. These dimers staple the cationic ribbons through the combination of N–H O hydrogen bonds in the manner depicted in Supplementary Material (Fig. S2). The Se–Se distance between two SeO2 4
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Fig. 2. Raman spectra of bis-4-BPPTSe measured at room temperature between (a) 1800–200 cm1 and (b) 3200–2800 cm1.
groups in [H4Se2O10]4 anions is 4.55 Å. The Se–O distances range from 1.6090(5) to 1.6407(5) as seen in Table 3. Vibrational study Experimental Raman and IR spectra of the title compound are presented in Fig. 2(a and b) and Fig. 3, respectively. The bands observed in the measured region 200–4000 cm1 arise from the vibrations of protons in the hydrogen bonds, the internal vibrations of the 4-BPP cations, selenate anions, water molecules and the vibrations of both N–H O and O–H O hydrogen bonds. The bands below 200 cm1 in the Raman spectrum arise from the lat-
tice vibrations of the crystal. In this work, we tried to give most precise assignment of the observed bands on the basis on our calculations as a preliminary source in the discussion and also by comparison with the previously reported experimental and theoretical vibrational studies of similar compounds. The vibration of SeO2 4 ions The vibrational analysis of an isolated SeO2 4 anion with Td point group symmetry leads to four fundamentals normal modes: v1(A1), v2(E), v3(F2) and v4(F2) with average wave numbers 837, 345, 873 and 415 cm1, respectively [17]. v1 and v3 involve the symmetric and the asymmetric stretching mode of the Se–O bonds, whereas
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Fig. 3. IR spectrum of bis-4-BPPTSe measured at room temperature between 4000 and 400 cm1.
v2 and v4 involve mainly O–Se–O symmetric and asymmetric bending modes. In the crystal, the symmetry of SeO2 4 ions is reduced from Td to C1. In fact, our structural study on 4-BPPTSe monohydrate shows that the Se–O distances and the O–Se–O angles are distorted with respect to the hypothetical Td symmetry. This symmetry change partially removes the degeneracies of the vibrational wave functions, which would have characterized free SeO2 4 anion. In the 200–1800 cm1 region, the SeO2 stretching and bending 4 vibrations expected to appear, as well as the modes associated to internal modes of the organic cation. However, in the light of present calculations and by comparison with similar compounds [18–21], we have been distinguishing between the bands originating from the vibrations of selenate groups and the 4-BPP cations. The bands observed at 794 and 787 cm1 in IR and Raman spectra respectively are assigned to the symmetric stretching v1 mode of selenate anion, whereas the corresponding asymmetric stretching mode v3 appear at 870 and 859 cm1 in IR spectrum and at 854 cm1 in Raman spectrum. The symmetric v2 and asymmetric v4 bending modes of selenate anion are observed at 330 and 418 cm1 in Raman spectrum respectively. No IR counterparts were observed either for v2 or for v4 types of vibration. As it can be seen from Table 4, the symmetric and asymmetric stretching and bending modes associated to SeO2 4 anion are well calculated. The vibration of 4-BPP cation As we have mentioned above, on the bases on our calculations as a preliminary source of assignment and by comparison with similar compounds, we made a reliable correspondence between experimental and calculated wave numbers. Benzene derivatives are the best recognized among the polyatomic systems as far as the vibrational spectra are discussed. The assignments of the benzene (/) ring vibrations are relatively easy because these vibrations are observed at very similar wavenumber in different compounds. The respective bands appear in the whole range of the spectrum [22]. Using the commonly accepted Wilson’s notation, these bands can be located for the studied salt in the following ranges: 3040– 3100 cm1 v(CH) stretching modes, 1000–1600 cm1 v(/) + d(CH) coupled stretching and in-plane bending modes, 700–1000 cm1
in plane d(/) mixed with out of plane bending c(CH) modes and 550–700 cm1 for the out of-plane bending c(/). For the assignment of the piperidinium u ring vibrations, the following description of the observed bands of 4-BPPSe is proposed:v(CH): 3000– 3070 cm1, v(u) + d(cH): 1000–1600 cm1, d(u): 700–1000 cm1 and c(u) + c(CH): 400–950 cm1. Detailed of assignment of al observed bands are quoted in Table 4. The vibration of water molecule The hydrogen atoms of water molecules act as a proton donors in hydrogen bonds of O–HW5 O type. HW5A atom participates in a very weak hydrogen bond in which O1 oxygen atom acts as a proton acceptor. According to X-ray data the length of this bond is equals 3.020 Å. The second hydrogen atom of water molecule, HW5B atom is engaged in a stronger hydrogen bond in which O4 oxygen atom acts as a proton acceptor. For this hydrogen bond interaction, the length resulting from structural investigations equals 2.782 Å. Due to such a rather big difference in the lengths of above mentioned bonds, the vibrations of water molecules manifest themselves as an independent two O–H stretching vibrations giving medium infrared bands at 3412 and 3341 cm1. Their Raman counterparts may not visible on the spectra, due to the insufficient sensitivity of Raman detector above 3200 cm1. The presence of water molecules is clearly manifested by the strong band observed in Raman spectrum at 1612 cm1. This band was attributed to in-plane deformation type of vibrations of water molecules d(H2O). The corresponding band due to the out-of-plane bending type of vibration of water molecule c(H2O) is observed in IR spectrum at 634 cm1 and at 619 cm1 in Raman spectrum. Vibrational dynamics of the hydrogen bonding The dynamics of the piperidinium hydrogen in the NH2 group predicts several types of normal modes: a stretching v(NH2), an in-plane bending d(NH2), an out-of-plane bending c(NH2), a rocking q(NH2), a twisting s(NH2) and a wagging mode x(NH2). These vibrations should be disturbed due to their participation in the hydrogen bond between the NH2 groups and O1, O2 and O3 oxygen atoms of the selenate anion. The second type of hydrogen bond
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Table 4 Observed and calculated frequencies (cm1) of bis-4-BPPTSe. Observed
Assignment with PED (%)a
Calculated
FT-IR
FT-Raman
B3LYP/6-31G
3412vs 3341vwsh 3207wb – – – – 3020wsh 2975vs 2846vwsh 2818s 2715s 2628w 2511w 2460w 2346m 2080wb 1978wb – 1592s 1480wsh 1447vs 1363wsh 1309w 1248w – – 1134w 1075m – – 970wsh 890vs 870vw 859w 794vwsh 720vs 695s 657vwsh 634vw 603vw 592s 487s – – – –
– – – 3078bsh 3060vvs 3048bsh 3032m 3018bw 2978bm – 2905w – – – – – – – 1612s 1589m – 1452w 1378w 1313w 1213vs 1189s 1178m 1108m 1040vvs 1007s 982w 960m – – 854m 787vs 750s 698vw – 619m 607w 582m 481m 440m 418m 330w 292vw
– 3492 3302 3092 3079 3061 3057 3040 3034 2923 2904 – – – 2456 2377 – – 1624 1607 1494 1462 1382 1317 1233 – – 1120 1065 1019 991 973 911 892 866 806 746 703 664 640 616 603 501 451 425 339 –
⁄
vas(H2O) vs(H2O)(98) vas(NH2)(96) v(CH)/(85) + v(OH)(12) v(CH)/(80)+v(CH)u(11) v(CH)/(87) v(CH)u(85) vs(NH2)(90) v(OH O)(84) v(NH O)(93) v(NH O)(96) – – – v(NH O)(77) + d(CH)u(12) v(NH O)(64) + v(CC)/(26) Benzene finger Benzene finger d(H2O)(78) + v(CC)/(16) v(CC)/(69) + v(CC)u(22) v(CC)/(56) + v(CC)u(15) s(CH2)(12) + d(CCH)/(58) v(CN)(73) + v(CC)u(12) v(CC)u(12) + d(CCH)u(56) v(CC)/(48) + d(CCH)/(22) q(NH2) d(CCH)/ + d(OH) d(NHO)(54) + d(CH)/ d(CC)/(42) + q(NH2)(22) + v(CC)u(12) d(CH)u(33) + d(CH)/(27) d(CH)/(33) + c(CH)(28) + v(CC)/(11) v(CC)u(42) + c(CH)u(12) d(CCH)/(46) + d(CH)(39) v3(SeO4)(67) v3(SeO4)(59) + v(CC)/(14) + d(CH)(16) v1(SeO4)(67) + v(CC)/(12) d(CCC)/(39) + c(CH)(19) c(CCC)u(42) + c(CCC)/(39) c(CCC)/(37) + s(NH2)(32) c(H2O)(61) + d(CH)(17) c(CCN)u(46) + c(CCC)/(21) + v(CN)u(13) c(CCN)u(38) + c(CCC)/(29) d(SeO4)(64) + d(CCH)/(18) c(NH2(52) + d(CH)(13) v4(SeO4)(67) + x(NH2)(17) v2(SeO4)(62) + d(CH)(12) c(/) + c(OH)
Abbreviations: /, benzene ring; u, piperidinium ring; s, strong; w, weak; v, very; sh, shoulder; b, broad; m, medium; v, stretching, d, in plane bending; c, out of plane bending; s, torsion mode; x, wagging; q, rocking. a
Only contribution P 10% listed.
appears between the oxygen atom of the water molecule O5 and two oxygen atoms (O4 and O1) of two adjacent selenate anions SeO2 4 with the mediation of HW5B and HW5A respectively forming a dimers. The assignment of the stretching v(NH O), the inplane bending d(NH O) and the out-of-plane bending c(NH O) vibrations to the respective bands was made on the basis on our calculations as a preliminary source and also from classical hydrogen bond theory presented in several reference works [23–26]. The hydrogen bonds length N–H O types range from 2.690 to 2.835 Å. This difference in lengths is manifested in IR spectrum through separate bands observed at 2975, 2846 and 2818 cm1. The inplane bending d(NH O) is observed at 1134 and 1108 cm1 in IR and Raman spectra respectively. Differential scanning calorimetric study DSC experiments were performed on heating the title compound from 270 to 400 K. The thermal analysis result is reported
in Supplementary Material (Fig. S3). The thermogram shows two endothermic peaks at almost 300 and 338 K. Temperatures of these transitions were determined by intercepting the baseline with the tangent to the left side of the peaks. These transitions may be interpreted by a dynamic order disorder which involves the structural modification of both anion and cation groups. Then, to approved our point of view and to gain more information on the nature of these transitions, we have undertaken a dielectric studies and a Raman scattering at several temperatures in the range 200–450 K. These results will be published as a separate work. Summary A new organic–inorganic, bis-4-benzyl piperidinium tetraoxoselenate monohydrate has been synthesized and characterized by X-ray diffraction, DSC measurement, IR and Raman vibrational study. The crystal formed is centro-symmetric. The 4-BPP cations are joined with the selenate anions through N–H O hydrogen
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bonds. The hydrogen atoms of water molecules act as a proton acceptors in hydrogen bonds of O–H O type linking two selenate anions and forming a centrosymmetric dimers. These dimers staple the cationic ribbons. The DSC measurement shows two endothermic peaks at almost 300 and 338 K. These transitions may be interpreted by a dynamic order disorder which involves the structural modification of both anion and cation groups. The structural and vibrational frequency analysis by PED calculations agree satisfactory with experimental results. On the basis on agreement between the experimental and calculated results, assignment of all fundamental vibrational modes of the title compound were examined and proposed in this investigation. Acknowledgment The authors thank Professor Istvan Mayer (Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary) for his help in theoretical calculations. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2012.07.133. References [1] R. Splingler, F. Zouari, A. Ben Salah, H. Burzlaff, Acta Crystallogr. C 53 (1997) 1566. [2] L. Antolini, G. Marcotrigiano, L. Menabue, G.C. Pellacani, Inorg. Chem. 18 (1979) 2652. [3] L.P. Battaglia, A. Bonamartini Corradi, G. Marcotrigiano, L. Menabue, G.C. Pellacani, Inorg. Chem. 19 (1980) 125. [4] Z. Elaoud, S. Al Juaid, T. Mhiri, A. Daoud, J. Alloys Compd. 442 (2007) 306. [5] S. Dehghanpour, A. Mahmoudi, M. khalaj, Acta Crystallogr. E 64 (2008) 19.
[6] Z. Elaoud, S. Kamoun, T. Mhiri, A. Daoud, A. Driss, J. Chem. Crystallogr. 34 (2004) 337. [7] I. Turki, Z. Elaoud, T. Mhiri, S. Kamoun, P. Graverau, S. Pechev, J. Chem. Crystallogr. 36 (2006) 111. [8] Z. Elaoud, S. Kamoun, J. Jaud, T. Mhiri, J. Chem. Crystallogr. 28 (1998) 313. [9] S. Kamoun, A. Jouini, A. Daoud, Acta Crystallogr. C 46 (1990) 1481. [10] S. Kamoun, A. Daoud, A. Elfakir, M. Quarton, I. Ledoux, Solid State Commun. 94 (1995) 893. [11] C. Lee, W.W. Yang, R.G. Parr, Phys. Rev. B. 41 (1988) 785. [12] D. Becke, J. Chem. Phys. 98 (1993) 5648. [13] R.G. Parr, W. Wang, Density-Functional Theory of Atoms and Molecules, Oxford University Press, New York, 1989. [14] M.J. Frish, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R.Cheeseman, V.G. Zakrzewski, J.A. Montgomery, J.R.E. Stramann, J.C.Burant, S. Dapprich, J.M. Millam, A.D. Daniels, K.N. Kudin, M.C. Stain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C.Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A. Petersson, P.Y. Agula, Q. Cui, K. Morkuma, D.K. Malick, A.D. Rabuck, K. Raghavachri, J.B.Foresman, J. Cioslowski, J.V. Ortiz, A.G. Baboul, B.B. Stefanov, G. Liv, A. Liashenko, P. Piskorz, I.Komaromi, R. Comperts, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkaray, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W.Wang, J.L. Andres, C. Gonzalez, M. Head-Gordon, E.S. Replogle, J.A. Pople, Gaussian 03, Revision D.01, Gaussian, Wallingford, 2004. [15] G. Rauhut, P. Pulay, J. Phys. Chem. 99 (1995) 3093. [16] M.H. Jamroz, Vibrational Energy Distribution Analysis VEDA 4, Warsaw, 2004. [17] R. Paetzold, H. Amouling, Z. Anorg, Allg. Chem. 317 (1962) 166. [18] J. Baran, M. Sledz, M. Drozd, A. Pietraszko, A. Haznar, H. ratajczak, J. Mol. Struct. 526 (2000) 361. [19] M.K. Marchewka, J. Janczak, S. Debrus, J. Baran, H. Ratajczak, Solid State Sci. 5 (2003) 643. [20] M. Drozd, J. Baran, A. Pietraszko, Spectrochim. Acta, Part A 61 (2005) 2775. [21] J. Polcek, D. Havlicek, I. Nemec, I. Cisarova, Z. Micka, Solid State Chem. 170 (2003) 308. [22] G. Versanyi, Assignments of Vibrational Spectra of Seven Hundred Benzene Derivatives, Academic Press, Budapest, New York, London (1–2 Adam Hilger, 1974). [23] S.N. Vinogradov, R.H. Linnell, Hydrogen Bonding, Van Nostrand Reinhold Company, New York, 1971. [24] A. Novak, Struct. Bonding 18 (1974) 177. [25] P. Schuster, G. Zundel, C. Sandorfy, The Hydrogen Bond Recent Developments in Theory and Experiments, North-Holland Publishing Company, Amsterdam,NewYork, Oxford, 1976. [26] G.A. Geffrey, An Introduction to Hydrogen Bonding, University Press, Oxford, 1977.
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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Structural, vibrational and DSC investigations of the bis-4-benzyl piperidinium tetraoxoselenate monohydrate crystal Y. Kessentini a,⇑, A. Ben Ahmed b, Z. Elaoud a, S.S. Aljuaid c, T. Mhiri a a
Laboratoire de l’Etat Solide, Faculté des Sciences de Sfax, BP. N° 1171, 3000 Sfax, Tunisia Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, BP. N° 1171, 3000 Sfax, Tunisia c Université de Roi Abdulaziz, Département de Chimie, Faculté des Sciences de Jeddah, Saudi Arabia b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" The 4-BPP crystallizes in the
monoclinic system P21/c. " Two peaks endothermic were shown
at almost 300 and 338 K. " Phase transitions may be interpreted
by a dynamic order disorder mechanism. " The experimental vibrational bands have been discussed and assigned to normal mode.
a r t i c l e
i n f o
Article history: Received 28 March 2012 Received in revised form 27 July 2012 Accepted 30 July 2012 Available online 19 August 2012 Keywords: 4-Benzyl piperidinium X-ray diffraction Vibrational study DFT calculations
a b s t r a c t A new organic–inorganic salt, bis-4-benzyl piperidinium tetraoxoselenate monohydrate has been synthesized and characterized by X-ray diffraction, FT-IR and FT-Raman spectroscopies. The title compound crystallizes in the monoclinic system P21/c at room temperature with the following parameters: a = 8.617(3) Å, b = 27.140(9) Å, c = 10.926(5) Å, b = 96.46(4)° and Z = 4. Its vibrational spectra have been discussed on the basis on quantum chemical density theory (DFT) calculation using B3LYP/6-31G⁄ approach. The role of the intermolecular interaction in this crystal is analyzed. Acidic protons of the selenate group were transferred to the organic cation giving the singly-protonated cation. The ability of ions to form spontaneous three-dimensional structure through O–H O and N–H O hydrogen bond is fully utilized. These hydrogen bonds give notable vibrational effects. Ó 2012 Elsevier B.V. All rights reserved.
Introduction There is still growing interest in the study of crystals containing 4-benzyl piperidinium cation (abbreviated here 4-BPP). Some compounds of the type bis-4-BPP-MX5 (M = Sb, Bi, Cu, Hg and X = Cl, Br) were studied almost 30 years ago to explain the behavior of 4-BPP molecule in the solid state [1–3]. Quite recently, the structure of 4-BPP dihydrogenmonophosphate [4], 4-BPP-1yl-methyl phosphate [5], 4-BPP monohydrogenphosphate pentahydrate [6] and 4-BPP bis-dihydrogenmonophosphate trihydrogenmonophosphate ⇑ Corresponding author. Tel.: +216 22778834. E-mail address: [email protected] (Y. Kessentini). 1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2012.07.133
[7] were published. Some 4-BPP salts crystallize in a noncentrosymmetric space group and exhibit nonlinear optical behavior [8–10]. Few papers with assignments of internal vibrations of 4-BPP molecule were already published. On the other hand, numerous selenate derivatives structural and vibrational studies have been published. The specific acidity of particular derivative allows one to choose appropriate base in crystal engineering of a new materials. In this work, we synthesized a new 4-BPP derivative: bis-4-benzyl piperidinium tetraoxoselenate monohydrate (abbreviated here bis-4-BPPTSe). The crystal is characterized by X-ray diffraction, DSC measurement, FT-IR absorption and FT-Raman scattering. Density functional theory calculation is used in order to perform structure analysis of the studied molecules. In
Y. Kessentini et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 98 (2012) 222–228 Table 1 Comparison between observed and calculated bonds lengths and bonds angles for the bis-4-BPPTSe. Parameters Bond length (Å) C(1)–C(2) C(1)–C(6) C(2)–C(3) C(3)–C(4) C(4)–C(5) C(4)–C(7) C(5)–C(6) C(7)–C(8) C(8)–C(9) C(8)–C(12) C(9)–C(10) C(10)–N(1) N(1)–C(11) C(11)–C(12) C(13)–C(14) C(13)–C(18) C(14)–C(15) C(15)–C(16) C(16)–C(17) C(16)–C(19) C(17)–C(18) C(19)–C(20) C(20)–C(21) C(20)–C(24) C(21)–C(22) C(22)–N(2) N(2)–C(23) C(23)–C(24) Bond angles (°) C(2)–C(1)–C(6) C(1)–C(2)–C(3) C(2)–C(3)–C(4) C(3)–C(4)–C(5) C(3)–C(4)–C(7) C(4)–C(5)–C(6) C(5)–C(6)–C(1) C(5)–C(4)–C(7) C(4)–C(7)–C(8) C(7)–C(8)–C(9) C(7)–C(8)–C(12) C(9)–C(8)–C(12) C(8)–C(9)–C(10) C(9)–C(10)–N(1) C(10)–N(1)–C(11) N(1)–C(11)–C(12) C(11)–C(12)–C(8) C(14)–C(13)–C(18) C(13)–C(14)–C(15) C(14)–C(15)–C(16) C(15)–C(16)–C(17) C(15)–C(16)–C(19) C(17)–C(16)–C(19) C(16)–C(17)–C(18) C(17)–C(18)–C(13) C(16)–C(19)–C(20) C(19)–C(20)–C(21) C(19)–C(20)–C(24) C(21)–C(20)–C(24) C(20)–C(21)–C(22) C(21)–C(22)–N(2) C(22)–N(2)–C(23) N(2)–C(23)–C(24)
Observed 1.359(12) 1.364(13) 1.347(11) 1.404(11) 1.386(10) 1.491(11) 1.367(11) 1.535(10) 1.512(9) 1.538(10) 1.538(8) 1.473(8) 1.475(8) 1.525(9) 1.317(13) 1.364(11) 1.393(12) 1.387(11) 1.372(11) 1.517(11) 1.396(12) 1.513(10) 1.494(11) 1.511(11) 1.522(10) 1.480(8) 1.470(9) 1.495(10) 119.08(1) 120.86(1) 122.49(9) 114.82(8) 123.97(8) 122.55(9) 120.16(9) 121.2(9) 114.58(7) 111.70(6) 107.75(7) 109.72(7) 109.62(6) 110.82(6) 112.07(6) 108.99(6) 111.23(7) 122.68(1) 116.65(1) 123.96(1) 116.9(9) 121.39(9) 121.64(9) 119.22(9) 120.54(9) 114.41(7) 113.27(7) 110.15(7) 110.19(7) 113.81(7) 109.36(6) 113.64(6) 111.09(7)
223
Experimental Synthesis
Calculated 1.395 1.396 1.387 1.401 1.401 1.515 1.395 1.546 1.540 1.540 1.530 1.486 1.495 1.526 1.355 1.396 1.396 1.401 1.401 1.515 1.397 1.545 1.520 1.540 1.530 1.484 1.495 1.529 119.23 120.12 121.01 117.82 121.27 121.02 120.13 120.52 114.40 112.38 110.09 109.74 111.85 110.56 113.39 110.52 110.52 120.13 119.52 121.01 118.20 120.44 121.33 120.99 120.12 114.24 112.38 111.13 109.81 111.99 110.06 113.96 109.70
the light of the theoretical calculation, correlation between FT-IR and FT-Raman spectra and computed results help unambiguous identification of vibrational modes and provide deeper insight into the bonding and structural features of the title compound.
The title compound was produced from aqueous solution containing high purity of 4-benzyl piperidine (purity 99%) and selenic acid in the stochiometric ratio 2:1. This mixture was steered and remained clear without any precipitate. After slow evaporation at room temperature, transparency crystals were obtained. X-ray data collection The X-ray data collection was carried out on Enraf-Nonus CAD4 four circle diffractometer using Mo-Ka radiation. A crystal of good quality was selected. The crystal structure was solved by direct method using SHELXS-97. Successive refinements based on F2 lead to a reliability factors of R = 0.0586. Anisotropy thermal displacement parameter refinement was used for all non-hydrogen atoms. Most of the hydrogen atoms attached to carbon and nitrogen were placed at geometrically calculated positions and refined with appropriate riding model. Crystal data and structure solution and refinement details are given in Supplementary Material (Table S1). The bis-4-BPPTSe crystallizes in the monoclinic P21/c system with the following unit cell dimensions: a = 8.617(3) Å; b = 27.140(9) Å; c = 10.926(5) Å and b = 96.46(4)°. Supplementary crystallographic data for this article in CIF format are available as Electronic Supplementary Publication from Cambridge Crystallographic Data Centre (CCDC 826114). Spectroscopic measurements The vibrational measurements were carried out at room temperature. Infrared spectra were taken on a BRUKER IFS-88 spectrometer in the region 4000–400 cm1. Resolution was set up to 2 cm1. Powder Fourier Transform Raman (FT-Raman) spectra were taken with an FRA-106 attachment to the BRUKER IFS-88 spectrometer. Nd3+:YAG air-cooled diode pumped laser of power ca. 200 mW was used as an exciting source. The incident laser excitation is 1064 nm. The scattered light was collected at the angle of 180°in the region 3600–80 cm1 and the resolution was set up to 2 cm1. The polycrystalline powders were achieved by grinding in agate mortar with pestle. Samples were put between KBr wafers. Differential scanning calorimetry Differential scanning calorimetry (DSC) measurements were performed on heating sample from 270 to 400 K on a SETARAM apparatus at a heating rate of 5 K mn1. Computational details The molecular structure of the title compound was fully optimized without any constraint at the Density Functional Theory (DFT) level using the Lee–Yang–Parr correlation functional (B3LYP/6-31G⁄) [11–13] implemented within Gaussian 03 program [14]. In order to take into account the effect of intermolecular interactions on geometrical parameters and vibrational spectroscopy, we have considered the cluster built up from two 4-BPP cations, one selenate anions and one water molecule linked by N–H O and O–H O hydrogen bonds. All the parameters were allowed to relax and all the calculations converged to an optimized geometry which corresponds to an energy minimum as revealed by the lack of imaginary values in the calculated wave numbers. Prior to compare the calculated vibrational wave numbers with the experimental counterparts, the former have been scaled by
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Fig. 1. Atom numbering scheme for bis-4-BPPTSe: (a) the experimental results and (b) the optimized geometry.
Table 2 Geometry of the hydrogen bonds in bis-4-BPPTSe crystal. D–H A
D–H (Å)
H A (Å)
D A (Å)
D–H A (°)
N1–H1A O3(i) N1–H1B O1(j) N2–H2A O1(j) N2–H2B O2(k) O5–HW5A O1(l) O5–HW5B O4(m)
0.90 0.90 0.90 0.90 0.99(2) 1.068(14)
1.82 1.91 1.94 1.80 2.07(4) 1.84(5)
2.704(8) 2.800(9) 2.835(7) 2.690(8) 3.020(8) 2.782(9)
167.2 170.4 176.0 172.3 158(8) 144(7)
Symmetry codes: (i) x + 1, y1/2, z + 1/2; (j) x, y + 3/2, z + 1/2; (k) x + 1, y1/ 2, z + 3/2 (l) x, y, z; (m) x + 1, y + 2, z.
Table 3 Geometry of the Se–O bonds in bis-4-BPPTSe crystal. Se
O(1)
O(2)
O(3)
O(4)
O(1) O(2) O(3) O(4)
1.6407(5) 108.68(2) 108.01(3) 108.06(3)
2.6451(2) 1.6144(4) 108.85(3) 109.38(3)
2.6354(5) 2.6272(3) 1.6157(6) 113.75(3)
2.6301(1) 2.6302(1) 2.7012(3) 1.6090(5)
0.963 scaling factor [15] to correct the evaluated wavenumbers for vibrational anharmonicity and deficiencies inherent to the computational level used. The vibrational modes were assigned on the basis of PED analysis using SQM program [16] and by comparison with the previous theoretical and experimental results reported in the literature for similar compounds. Results and discussions Structure description The title crystal belongs to the P21/c space group of monoclinic system with four formula units in unit cell (Z = 4). It was supposed, that during the complex formation, the acidic protons of the selenate group were transferred to the 4-BPP molecules giving the singly-protonated 4-BPP cation. This statement is in accordance with the crystallographic data. It follows from them that the asymmetric unit comprises ionized selenate anion SeO2 4 , tow singly-proton-
ated 4-BPP cation [C6H5CH2C5H9NH2]+ and water molecule. Selected bonds length and angles together with the calculated ones are presented in Table 1 in accordance with the atom numbering scheme given in Fig. 1a. Optimized geometry of the title compound model is presented in Fig 1b. As seen in Table 1, most of the computed bonds are slightly longer than experimental one. This discrepancies can be explained by the fact that the calculation relates to the isolated molecule where the intermolecular Coulombic interaction with the neighboring molecules are absent, whereas the experimental result corresponds to interacting molecules in the crystal lattice. The maximum difference does not exceed 0.04 Å for the bond lengths and 3.5° for the bond angles. This result shows that the cluster approach is sufficient to the analysis of the spectra in the solid state. The various hydrogen bond parameters are summarized in Table 2. The hydrogen atoms from selenate group was transferred to N(1) and N(2) atoms of 4-BPP rings. The 4-BPP cations do not differ significantly and exhibit the characteristic deformation of the aromatic ring from the ideal hexagonal form. The internal C10–N1–C11 angle (112.07(6)°) protonated at the N atom is significantly greater than other angles within the piperidine ring: C12–C8–C9 (109.72(7)°), C8–C9–C10 (109.62(6)°), C9–C10–N1 (110.82(6)°), N1–C11–C12 (108.99(6)°) and C11–C12–C8 (111.23(7)°). The same situation is observed for C22–N2–C23 angle. It is worthwhile mentioning, that in recently determined structure of 4-BPP dihydrogenmonophosphate pentahydrate [6] and 4-BPP dihydrogenmonophosphate trihydrogenmonophosphate [7] the piperidine ring exhibit similar pattern of the internal C–N–C angle. Bis-4-BPPTSe monohydrate is a new organo-selenate consisting of a structure with strong two dimensional characters based on sheets of SeO2 4 tetrahedron and water molecule fused together via H(OW)–O–Se bonds. The SeO2 4 tetrahedra are associated in pairs through water molecules forming centrosymetric finite clusters [H4Se2O10]4 (for details see Supplementary Material, Fig. S1). These dimers are located at z ¼ 0andz ¼ 12. The 4-BPP cations are joined with the selenate anions through N1– H1A O3, N1–H1B O1, N2–H2B O2 and N2–H2A O1, hydrogen bonds with the lengths ranging from 2.690(8) to 2.835(7) Å. These dimers staple the cationic ribbons through the combination of N–H O hydrogen bonds in the manner depicted in Supplementary Material (Fig. S2). The Se–Se distance between two SeO2 4
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225
Fig. 2. Raman spectra of bis-4-BPPTSe measured at room temperature between (a) 1800–200 cm1 and (b) 3200–2800 cm1.
groups in [H4Se2O10]4 anions is 4.55 Å. The Se–O distances range from 1.6090(5) to 1.6407(5) as seen in Table 3. Vibrational study Experimental Raman and IR spectra of the title compound are presented in Fig. 2(a and b) and Fig. 3, respectively. The bands observed in the measured region 200–4000 cm1 arise from the vibrations of protons in the hydrogen bonds, the internal vibrations of the 4-BPP cations, selenate anions, water molecules and the vibrations of both N–H O and O–H O hydrogen bonds. The bands below 200 cm1 in the Raman spectrum arise from the lat-
tice vibrations of the crystal. In this work, we tried to give most precise assignment of the observed bands on the basis on our calculations as a preliminary source in the discussion and also by comparison with the previously reported experimental and theoretical vibrational studies of similar compounds. The vibration of SeO2 4 ions The vibrational analysis of an isolated SeO2 4 anion with Td point group symmetry leads to four fundamentals normal modes: v1(A1), v2(E), v3(F2) and v4(F2) with average wave numbers 837, 345, 873 and 415 cm1, respectively [17]. v1 and v3 involve the symmetric and the asymmetric stretching mode of the Se–O bonds, whereas
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Fig. 3. IR spectrum of bis-4-BPPTSe measured at room temperature between 4000 and 400 cm1.
v2 and v4 involve mainly O–Se–O symmetric and asymmetric bending modes. In the crystal, the symmetry of SeO2 4 ions is reduced from Td to C1. In fact, our structural study on 4-BPPTSe monohydrate shows that the Se–O distances and the O–Se–O angles are distorted with respect to the hypothetical Td symmetry. This symmetry change partially removes the degeneracies of the vibrational wave functions, which would have characterized free SeO2 4 anion. In the 200–1800 cm1 region, the SeO2 stretching and bending 4 vibrations expected to appear, as well as the modes associated to internal modes of the organic cation. However, in the light of present calculations and by comparison with similar compounds [18–21], we have been distinguishing between the bands originating from the vibrations of selenate groups and the 4-BPP cations. The bands observed at 794 and 787 cm1 in IR and Raman spectra respectively are assigned to the symmetric stretching v1 mode of selenate anion, whereas the corresponding asymmetric stretching mode v3 appear at 870 and 859 cm1 in IR spectrum and at 854 cm1 in Raman spectrum. The symmetric v2 and asymmetric v4 bending modes of selenate anion are observed at 330 and 418 cm1 in Raman spectrum respectively. No IR counterparts were observed either for v2 or for v4 types of vibration. As it can be seen from Table 4, the symmetric and asymmetric stretching and bending modes associated to SeO2 4 anion are well calculated. The vibration of 4-BPP cation As we have mentioned above, on the bases on our calculations as a preliminary source of assignment and by comparison with similar compounds, we made a reliable correspondence between experimental and calculated wave numbers. Benzene derivatives are the best recognized among the polyatomic systems as far as the vibrational spectra are discussed. The assignments of the benzene (/) ring vibrations are relatively easy because these vibrations are observed at very similar wavenumber in different compounds. The respective bands appear in the whole range of the spectrum [22]. Using the commonly accepted Wilson’s notation, these bands can be located for the studied salt in the following ranges: 3040– 3100 cm1 v(CH) stretching modes, 1000–1600 cm1 v(/) + d(CH) coupled stretching and in-plane bending modes, 700–1000 cm1
in plane d(/) mixed with out of plane bending c(CH) modes and 550–700 cm1 for the out of-plane bending c(/). For the assignment of the piperidinium u ring vibrations, the following description of the observed bands of 4-BPPSe is proposed:v(CH): 3000– 3070 cm1, v(u) + d(cH): 1000–1600 cm1, d(u): 700–1000 cm1 and c(u) + c(CH): 400–950 cm1. Detailed of assignment of al observed bands are quoted in Table 4. The vibration of water molecule The hydrogen atoms of water molecules act as a proton donors in hydrogen bonds of O–HW5 O type. HW5A atom participates in a very weak hydrogen bond in which O1 oxygen atom acts as a proton acceptor. According to X-ray data the length of this bond is equals 3.020 Å. The second hydrogen atom of water molecule, HW5B atom is engaged in a stronger hydrogen bond in which O4 oxygen atom acts as a proton acceptor. For this hydrogen bond interaction, the length resulting from structural investigations equals 2.782 Å. Due to such a rather big difference in the lengths of above mentioned bonds, the vibrations of water molecules manifest themselves as an independent two O–H stretching vibrations giving medium infrared bands at 3412 and 3341 cm1. Their Raman counterparts may not visible on the spectra, due to the insufficient sensitivity of Raman detector above 3200 cm1. The presence of water molecules is clearly manifested by the strong band observed in Raman spectrum at 1612 cm1. This band was attributed to in-plane deformation type of vibrations of water molecules d(H2O). The corresponding band due to the out-of-plane bending type of vibration of water molecule c(H2O) is observed in IR spectrum at 634 cm1 and at 619 cm1 in Raman spectrum. Vibrational dynamics of the hydrogen bonding The dynamics of the piperidinium hydrogen in the NH2 group predicts several types of normal modes: a stretching v(NH2), an in-plane bending d(NH2), an out-of-plane bending c(NH2), a rocking q(NH2), a twisting s(NH2) and a wagging mode x(NH2). These vibrations should be disturbed due to their participation in the hydrogen bond between the NH2 groups and O1, O2 and O3 oxygen atoms of the selenate anion. The second type of hydrogen bond
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227
Table 4 Observed and calculated frequencies (cm1) of bis-4-BPPTSe. Observed
Assignment with PED (%)a
Calculated
FT-IR
FT-Raman
B3LYP/6-31G
3412vs 3341vwsh 3207wb – – – – 3020wsh 2975vs 2846vwsh 2818s 2715s 2628w 2511w 2460w 2346m 2080wb 1978wb – 1592s 1480wsh 1447vs 1363wsh 1309w 1248w – – 1134w 1075m – – 970wsh 890vs 870vw 859w 794vwsh 720vs 695s 657vwsh 634vw 603vw 592s 487s – – – –
– – – 3078bsh 3060vvs 3048bsh 3032m 3018bw 2978bm – 2905w – – – – – – – 1612s 1589m – 1452w 1378w 1313w 1213vs 1189s 1178m 1108m 1040vvs 1007s 982w 960m – – 854m 787vs 750s 698vw – 619m 607w 582m 481m 440m 418m 330w 292vw
– 3492 3302 3092 3079 3061 3057 3040 3034 2923 2904 – – – 2456 2377 – – 1624 1607 1494 1462 1382 1317 1233 – – 1120 1065 1019 991 973 911 892 866 806 746 703 664 640 616 603 501 451 425 339 –
⁄
vas(H2O) vs(H2O)(98) vas(NH2)(96) v(CH)/(85) + v(OH)(12) v(CH)/(80)+v(CH)u(11) v(CH)/(87) v(CH)u(85) vs(NH2)(90) v(OH O)(84) v(NH O)(93) v(NH O)(96) – – – v(NH O)(77) + d(CH)u(12) v(NH O)(64) + v(CC)/(26) Benzene finger Benzene finger d(H2O)(78) + v(CC)/(16) v(CC)/(69) + v(CC)u(22) v(CC)/(56) + v(CC)u(15) s(CH2)(12) + d(CCH)/(58) v(CN)(73) + v(CC)u(12) v(CC)u(12) + d(CCH)u(56) v(CC)/(48) + d(CCH)/(22) q(NH2) d(CCH)/ + d(OH) d(NHO)(54) + d(CH)/ d(CC)/(42) + q(NH2)(22) + v(CC)u(12) d(CH)u(33) + d(CH)/(27) d(CH)/(33) + c(CH)(28) + v(CC)/(11) v(CC)u(42) + c(CH)u(12) d(CCH)/(46) + d(CH)(39) v3(SeO4)(67) v3(SeO4)(59) + v(CC)/(14) + d(CH)(16) v1(SeO4)(67) + v(CC)/(12) d(CCC)/(39) + c(CH)(19) c(CCC)u(42) + c(CCC)/(39) c(CCC)/(37) + s(NH2)(32) c(H2O)(61) + d(CH)(17) c(CCN)u(46) + c(CCC)/(21) + v(CN)u(13) c(CCN)u(38) + c(CCC)/(29) d(SeO4)(64) + d(CCH)/(18) c(NH2(52) + d(CH)(13) v4(SeO4)(67) + x(NH2)(17) v2(SeO4)(62) + d(CH)(12) c(/) + c(OH)
Abbreviations: /, benzene ring; u, piperidinium ring; s, strong; w, weak; v, very; sh, shoulder; b, broad; m, medium; v, stretching, d, in plane bending; c, out of plane bending; s, torsion mode; x, wagging; q, rocking. a
Only contribution P 10% listed.
appears between the oxygen atom of the water molecule O5 and two oxygen atoms (O4 and O1) of two adjacent selenate anions SeO2 4 with the mediation of HW5B and HW5A respectively forming a dimers. The assignment of the stretching v(NH O), the inplane bending d(NH O) and the out-of-plane bending c(NH O) vibrations to the respective bands was made on the basis on our calculations as a preliminary source and also from classical hydrogen bond theory presented in several reference works [23–26]. The hydrogen bonds length N–H O types range from 2.690 to 2.835 Å. This difference in lengths is manifested in IR spectrum through separate bands observed at 2975, 2846 and 2818 cm1. The inplane bending d(NH O) is observed at 1134 and 1108 cm1 in IR and Raman spectra respectively. Differential scanning calorimetric study DSC experiments were performed on heating the title compound from 270 to 400 K. The thermal analysis result is reported
in Supplementary Material (Fig. S3). The thermogram shows two endothermic peaks at almost 300 and 338 K. Temperatures of these transitions were determined by intercepting the baseline with the tangent to the left side of the peaks. These transitions may be interpreted by a dynamic order disorder which involves the structural modification of both anion and cation groups. Then, to approved our point of view and to gain more information on the nature of these transitions, we have undertaken a dielectric studies and a Raman scattering at several temperatures in the range 200–450 K. These results will be published as a separate work. Summary A new organic–inorganic, bis-4-benzyl piperidinium tetraoxoselenate monohydrate has been synthesized and characterized by X-ray diffraction, DSC measurement, IR and Raman vibrational study. The crystal formed is centro-symmetric. The 4-BPP cations are joined with the selenate anions through N–H O hydrogen
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bonds. The hydrogen atoms of water molecules act as a proton acceptors in hydrogen bonds of O–H O type linking two selenate anions and forming a centrosymmetric dimers. These dimers staple the cationic ribbons. The DSC measurement shows two endothermic peaks at almost 300 and 338 K. These transitions may be interpreted by a dynamic order disorder which involves the structural modification of both anion and cation groups. The structural and vibrational frequency analysis by PED calculations agree satisfactory with experimental results. On the basis on agreement between the experimental and calculated results, assignment of all fundamental vibrational modes of the title compound were examined and proposed in this investigation. Acknowledgment The authors thank Professor Istvan Mayer (Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary) for his help in theoretical calculations. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2012.07.133. References [1] R. Splingler, F. Zouari, A. Ben Salah, H. Burzlaff, Acta Crystallogr. C 53 (1997) 1566. [2] L. Antolini, G. Marcotrigiano, L. Menabue, G.C. Pellacani, Inorg. Chem. 18 (1979) 2652. [3] L.P. Battaglia, A. Bonamartini Corradi, G. Marcotrigiano, L. Menabue, G.C. Pellacani, Inorg. Chem. 19 (1980) 125. [4] Z. Elaoud, S. Al Juaid, T. Mhiri, A. Daoud, J. Alloys Compd. 442 (2007) 306. [5] S. Dehghanpour, A. Mahmoudi, M. khalaj, Acta Crystallogr. E 64 (2008) 19.
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