untitled European Journal of Chemistry 4 (2) (2013) 117‐120 European Journal of Chemistry ISSN 2153‐2249 (Print) / ISSN 2153‐2257 (Online)  2013 EURJCHEM DOI:10.5155/eurjchem.4.2.117‐120.738 European Journal of Chemistry Journal homepage: www.eurjchem.com Crystal structure and spectroscopic study of bis‐tetrapropylammonium hexachlorodicuprate(II), [N(C3H7)4]2Cu2Cl6 Ikram Dhouib a,*, Philippe Guionneau b, Stanislav Pechev b, Tahar Mhiri a and Zakaria Elaoud a a Laboratoire de Physico‐Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, Sfax 3000, Tunisie b CNRS, Université de Bordeaux, ICMCB, 87 avenue du Dr A. Schweitzer, Pessac, F‐33608, France *Corresponding author at: Laboratoire de Physico‐Chimie de l’Etat Solide, Département de Chimie, Faculté des Sciences de Sfax, Université de Sfax, Sfax 3000, Tunisie. Tel.: +2.169.7019206; fax: +2.167.4274437. E‐mail address: ikramdhouib82@yahoo.fr (I. Dhouib). ARTICLE INFORMATION ABSTRACT Received: 17 January 2013 Accepted: 23 January 2013 Online: 30 June 2013 KEYWORDS Single crystals of the bis‐tetrapropylammonium hexachlorodicuprate(II), [N(C3H7)4]2Cu2Cl6, were grown by slow evaporation solution technique at room temperature. The compound was characterized by Raman, IR and single crystal X‐ray diffraction studies. Crystal data for C12H28Cl3CuN (M = 356.24 g/mol): triclinic, space group P‐1 (no. 2), a = 9.3851(2) Å, b = 9.3844(2) Å, c = 11.8837(3) Å, α = 106.3330(11)°, β = 100.0280(12)°, γ = 113.2830(12)°, V = 872.95(3) Å3, Z = 2, T = 293(2) K, μ(MoKα) = 1.693 mm‐1, Dcalc = 1.355 g/mm3, 8056 reflections measured (6.64 ≤ 2Θ ≤ 62.02), 5526 unique (Rint = 0.0303) which were used in all calculations. The final R1 was 0.0427 (>2σ(I)) and wR2 was 0.1312 (all data). The atomic arrangement can be described by alternating organic and inorganic layers parallel to the (101) plan, made up of tetrapropylammonium groups and Cu2Cl6 dimers, respectively. In crystal structure, the inorganic layers, built up by Cu2Cl6 dimers, are connected to the organic ones through hydrogen bonding C‐H…Cl and Van der Waals interaction in order to build cation‐anion‐cation cohesion. These interactions cause to the formation of a three‐dimensional supramolecular architecture. Single crystal Copper(II) complex Spectroscopic study Tetrapropylammonium Hexachlorodicuprate(II) Crystal structure analysis 1. Introduction The combination of organic molecules and inorganic materials was the starting point for the development of new hybrid compounds, with expected physical and chemical properties. These compounds have attracted great attention because of their unique opportunity to combine the remarkable features of organic compounds with those of inorganic materials. Their applications have been explored and reported in various fields, such as magnetism, conductive, luminescence and optical properties [1‐5]. The materials based upon substituted complex ammoniums with halogenated metals such as Hg, Cd, Zn, Mn and Cu etc. present very interesting physical properties [6‐12]. The large structural variability of copper(II) due to the presence of an active Jahn‐Teller effect in the d9 electronic system and the relative flatness of the potential surfaces make the thermochromism in chlorocuprates of continual interest. These compounds and their properties are of interest not only in inorganic chemistry but also in fields ranging from solid‐ state physics to bioinorganic chemistry. Among solid‐state physicists and chemists, there is a great interest in the copper(II) halides owing to the plasticity of the metal coordination sphere which leads to a great variety of crystalline architectures with different coordination numbers, geometries and nuclearities, and makes copper systems as excellent candidates for analysing correlations between structural parameters and magnetic properties [13‐17]. On the other hand, compounds crystallized with aliphatic tetra‐ammonium cations with general formula (CnH2n+1)4N+, such as (CH3)4N+, (C2H5)4N+, (C3H7)4N+, undergo many structural phase transitions governed by the reorientational dynamics of the tetra‐alkyl‐ammonium groups [10,12,18]. In fact, a variety of compounds are formed by the reaction of mixed tetra‐alkyl‐ammonium with halogenated metals where n ≤ 2. Furthermore, the crystalline structure of these derivate can be described as a sequence of alternating layers of MX4 tetrahedra; the organic chains are inserted between these sheets. The Cu2Cl62‐ polyhedra can be described as two distorted tetrahedrons composed of two groups of CuCl4 tetrahedra sharing two chlorines with a symmetry center in between. It accounts for the synthesis, the structural characterization by X‐ ray diffraction, IR and Raman spectroscopy of the bis‐ tetrapropylammonuim hexachlorodicuprate(II), [N(C3H7)4]2 Cu2Cl6. 2. Experimental 2.1. Synthesis The title compound was prepared by mixing (CH3CH2CH2)4NOH (1 mmol), CuCl2.2H2O (2 mmol), concentrated HCl (1 mL) and water (10 mL). The mixture was then allowed to stand and evaporate slowly at room temperature. After 3 days, brown crystals appeared and they were studied by single crystal X‐ray diffraction. The analysis of the obtained phase confirms the formation of [(CH3CH2CH2)4N]2Cu2Cl6. 2.2. Characterizations The infrared spectrum was recorded in the range 700‐4000 cm‐1 with a “Perkin Elmer FTIR‐1000” spectrophotometer using a sample dispersed in a KBr pellet. 118 Dhouib et al. / European Journal of Chemistry 4 (2) (2013) 117‐120 Figure 1. The asymmetric unit of [(CH3CH2CH2)4N]2Cu2Cl6. Back scattering Raman spectra were obtained under microscope with a T‐64000 Raman spectrometer (ISA, Jobin Yvon) in the 50‐4050 cm‐1 range. 2.3. X‐ray single crystal structure determination Single crystal X‐ray diffraction data of the title compound were collected at room temperature on a Nonius Kappa‐CCD diffractometer using Mo‐Kα radiation (λ = 0.71073 Å) through the program COLLECT [19]. Correction for Lorentz‐polarisation effect, peak integration and background determination were carried out with the program DENZO [20]. Frame scaling and unit cell parameters refinement were performed with the program SCALEPACK [20]. Pertinent details of the crystal structure of [(CH3CH2CH2)4N]2Cu2Cl6 are listed in Table 1. The crystal structure has been solved and refined in the triclinic symmetry, space group P‐1, using the WINGX environment [21] and based on SHELXS97 [22] and SHELXL97 [23]. All the hydrogen positions of the diprotonated cation were placed geometrically and held in the riding mode. The C‐H bonds were fixed and affined at 0.76 and 1.05 Å. Bond distances and angles calculated from the final atomic coordinates, as well as probable hydrogen bonds, are given in Table 2 and 3, respectively. Table 1. Crystal data and structure refinement of [(CH3CH2CH2)4N]2Cu2Cl6. Empirical formula C12H28Cl3CuN Formula weight, g/mol 356.24 Color Brown Temperature, K 293(2) Crystal system Triclinic Space group P‐1 a, Å 9.3851(2) b, Å 9.3844(2) c, Å 11.8837(3) α, ° 106.3330(11) β, ° 100.0280(12) γ, ° 113.2830(12) Volume, Å3 872.95(3) Z 2 ρcalc, mg/mm3 1.355 , mm‐1 1.693 F(000) 374.0 Diffractometer/scan KAPPA CCD. Enraf‐Nonius Radiation, graphite monochromater Mo Kα (λ = 0.71073 Å) Crystal size, mm3 0.2 × 0.2 × 0.12 2Θ range for data collection 6.64 to 62.02° Index ranges ‐13 ≤ h ≤ 13, ‐13 ≤ k ≤ 13, ‐17 ≤ l ≤ 17 Reflections collected 8056 Independent reflections 5526 [R(int) = 0.0303] Data/restraints/parameters 5526/0/194 Goodness‐of‐fit on F2 1.046 Final R indexes [I>=2σ (I)] R1 = 0.0427, wR2 = 0.1208 Final R indexes [all data] R1 = 0.0589, wR2 = 0.1312 Largest diff. peak/hole, e Å‐3 0.76/‐0.63 3. Results and discussion 3.1. Structural analysis The asymmetric unit is composed of half [Cu2Cl6]2‐ anion and one [(CH3CH2CH2)4N]+ cation (Figure 1). The Cu‐Cl distances are about similar (Table 2). The Cu‐Cl bond distances are in the range of 2.2046(6)‐2.3231(6) Å for the Cu2Cl62‐ anion. These bond distances fall in the range reported previously for compounds containing Cu‐Cl bonds [24‐28]. The Cl‐Cu‐Cl angles are present in two distinguished sets. The first contains four angles of 96.31(2) and 147.66(3) ° which are much lower than the other set which contains two angles of 97.20(3) and 146.13(3) °. These distortions are typically measured by the value of the mean trans and cis‐Cl‐Cu‐Cl angle, which is 146.895 ° and 97.366 °, respectively. Accordingly the geometry of Cu2Cl62‐ anion is highly distorted around the Cu(II) ion, which in fact, is always distorted. The coordination about each copper is intermediate between a planar and a tetrahedral arrangement of four chlorine ligands, Cu(1)‐Cl(2) (2.3152(6) Å) [29]. The principal feature of the crystal structure is the existence of essentially isolated [Cu2Cl6]2‐ dimmers with a copper‐chlorine‐ copper angle of 94.45(2)o. By space group symmetry requirements, the dimers have only a centre of symmetry connects the respective equivalent pairs of Cu(1), Cl(2), Cl(3) and Cl(4). The copper‐copper separation in the dimer is in the value of 3.405 Å. The structural arrangement of [N(C3H7)4]2Cu2Cl6 can be described as an alternation of organic [N(C3H7)4]+ groups and inorganic Cu2Cl6 dimers (Figure 2). The lengths of the N‐C bonds are in the range between 1.518(2) and 1.526(3) Å. The C‐N‐C angles range from 105.15(15) to 111.77(16) °. The C‐C bonds lengths are in the region between 1.495(4) and 1.521(3) Å. In these layers each [Cu2Cl6]2‐ anion is interacting with ten surrounding cations via five C‐H…Cl. Each organic cation engages its hydrogen atoms bonded to C atoms in C‐H…Cl hydrogen bonds. Accordingly, it is connected to anions and participates in the structure cohesion. The intermolecular distances C…Cl vary from 3.712(3) to 3.858(2) Å and the C‐H…Cl angles range between 128(3) and 167(2) °. 3.2. Spectroscopic studies The FT‐IR and FT‐Raman spectra of the title compound were measured for the powder sample at room temperature. Vibrational spectra are shown in Figures S1 and S2. The frequencies observed in the infrared spectra at 2997 and 2987 cm‐1 are assigned respectively to the νas and νs of CH2, CH3 groups. The different modes of asymmetric (δas) and symmetric (δs) deformation of the methyl groups are found at Dhouib et al. / European Journal of Chemistry 4 (2) (2013) 117‐120 119 1385 and 1354 cm‐1, respectively. A weak band which appeared at 1371 cm‐1 is related to the C‐C and C‐N vibration [30,31]. Besides, sharp bands observed in IR at 1111, 1139 and in Raman at 1059, 1035 cm‐1 are associated to CH3 and CH2 rocking vibration modes respectively. The band observed at 970 cm‐1 in IR and 957 cm‐1 in Raman were assigned to ν1(NC4) stretching modes [32‐34]. The deformation mode ν2(NC4) appears at 765 and 753 cm‐1 in IR and Raman spectrum, respectively. The splitting ν(C‐C‐C‐N) bending mode at 772 cm‐1 may correspond to different conformers of the organic chains. The band observed at 478 cm‐1 in Raman spectrum arises from the deformation vibration ν4(NC4) of the TPCu entity. Table 2. Selected bond lengths and bond angles of [(CH3CH2CH2)4N]2Cu2Cl6. Bond length, Å Bond length, Å Cu1‐Cl2 2.3152(6) C1‐C8 1.505(3) Cu1‐Cl21 2.3231(6) C2‐C6 1.512(3) Cu1‐Cl3 2.2046(6) C3‐C7 1.521(3) Cu1‐Cl4 2.2130(6) C4‐C9 1.513(4) Cl2‐Cu11 2.3231(6) C5‐C6 1.495(4) N1‐C1 1.521(3) C11‐C7 1.512(4) N1‐C2 1.525(3) C8‐C10 1.516(4) N1‐C3 1.518(2) C9‐C12 1.520(4) N1‐C4 1.526(3) Bond angle, ˚ Bond angle, ˚ Cl2‐Cu1‐Cl21 85.55(2) C3‐N1‐C2 111.34(16) Cl3‐Cu1‐Cl21 146.13(3) C3‐N1‐C4 111.77(16) Cl3‐Cu1‐Cl2 96.31(2) C8‐C1‐N1 116.40(18) Cl3‐Cu1‐Cl4 98.80(3) C6‐C2‐N1 116.30(19) Cl4‐Cu1‐Cl21 97.20(3) N1‐C3‐C7 116.19(17) Cl4‐Cu1‐Cl2 147.66(3) C9‐C4‐N1 116.07(19) Cu1‐Cl2‐Cu11 94.45(2) C5‐C6‐C2 110.3(2) C1‐N1‐C2 111.36(17) C11‐C7‐C3 108.6(2) C1‐N1‐C4 111.46(16) C1‐C8‐C10 109.5(2) C2‐N1‐C4 105.89(15) C4‐C9‐C12 109.5(3) C3‐N1‐C1 105.15(15) Torsion angle, ˚ Torsion angle, ˚ Cl21‐Cu1‐Cl2‐Cu11 0.0 C2‐N1‐C1‐C8 57.3(3) Cl3‐Cu1‐Cl2‐Cu11 146.03(3) C2‐N1‐C3‐C7 ‐60.8(2) Cl4‐Cu1‐Cl2‐Cu11 ‐96.44(5) C2‐N1‐C4‐C9 ‐179.4(2) N1‐C1‐C8‐C10 177.9(2) C3‐N1‐C1‐C8 178.0(2) N1‐C2‐C6‐C5 ‐172.1(2) C3‐N1‐C2‐C6 ‐60.5(3) N1‐C3‐C7‐C11 178.41(19) C3‐N1‐C4‐C9 59.2(3) N1‐C4‐C9‐C12 176.4(2) C4‐N1‐C1‐C8 ‐60.7(3) C1‐N1‐C2‐C6 56.5(3) C4‐N1‐C2‐C6 177.9(2) C1‐N1‐C3‐C7 178.5(2) C4‐N1‐C3‐C7 57.4(3) C1‐N1‐C4‐C9 ‐58.1(3) 1 Symmetry code: 1‐x, 1‐y, 1‐z Table 3. Hydrogen bonds for the title compound. D‐H…A * d(D‐H) (Å) d(H…A) (Å) d(D…A) (Å)  D‐H…A (°) C5‐H5C...Cl3i 0.96 2.97 3.816(3) 147.9 C11‐H11A...Cl2ii 0.96 2.95 3.821(3) 151.5 C6‐H7...Cl2iii 1.05(4) 2.97(5) 3.712(3) 128(3) C11‐H11B...Cl2 0.96 2.92 3.832(3) 158.6 C1‐H16...Cl3 0.88(3) 3.00(3) 3.858(2) 167(2) * Symmetry codes: i: x+1, y, z; ii: ‐x+2, ‐y+1, ‐z+1; iii: ‐x+2, ‐y+2, ‐z+1. Figure 2. Projection along the a axis of the atomic arrangement of [(CH3CH2CH2)4N]2Cu2Cl6. The Raman and IR active bands involving mainly the Cu2Cl6 vibration can be proposed by comparison with Ga2Cl6 [35]. The isolated inorganic entities exhibit D2h symmetry with 18 normal modes. In this framework, among the 10 Cu2Cl6 Raman active modes, the 455, 311, 189, 98, 246 and 128 cm‐1 lines can be assigned to the 4Ag (ν1‐ν4) and 2B1g (ν6, ν7), respectively. In the end, the 2B2g (ν11, ν12) modes occur at 611 cm‐1 of ν11 and 118 cm‐1 of ν12. The bands observed at 197 and 373 cm‐1 are assigned to the B3g (ν15) and B2g (ν18) modes, respectively. The B1u (ν8), 2B2u (ν13, ν14) and 2 B3u (ν16, ν17) modes are active in the IR spectra. Like in Ga2Cl6, only one (ν8) over the 3 B1u is observed. In the reported study only ν8 is observed. The ν1, ν8, ν11 and ν16 vibrations due to the CuCl2 stretching motions and their frequencies are higher than those of ν2, ν6, ν13 and ν17 that witch are mainly due to the vibrations of the bridging Cu2Cl6 groups. 4. Conclusion Bis‐tetrapropylammonium hexachlorodicuprate(II), [N(C3H7)4]2Cu2Cl6, has been prepared and studied by single crystal X‐ray diffraction and IR spectroscopy. The crystal packing of the salt [N(C3H7)4]2Cu2Cl6 is based on inorganic Cu2Cl6 units surrounded by organic N(C3H7)4 entities into a triclinic crystal lattice symmetry. Acknowledgements Grateful thanks are expressed to Dr. Philippe Guionneau (Service Rayons X, ICMCB/CNRS Bordeaux) for the X‐ray data collection. 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