Infrared, polarized Raman and ab initio calculations of the vibrational spectra of [N(C3H7)4]2Cu2Cl6 crystals

• DOI: 10.1016/j.vibspec.2012.10.002
• Publication Date: 2012-10-24T12:30:12Z
• Authors: Abderrazek Oueslati; Alain Bulou; Florent Calvayrac; Karim Adil; Mohamed Gargouri; Faouzi Hlel
• Keywords: Triclinic crystal system

Abstract The room temperature structure of crystallized [N(C 3 H 7 ) 4 ] 2 Cu 2 Cl 6 is triclinic with P 1 ¯ space group. It exhibits two sublattices made up of [Cu 2 Cl 6 ] 2− bitetrahedra and tetrapropylammonium N(C 3 H 7 ) 4 + layers. The vibrational characteristics have been measured at room temperature by infrared spectroscopy (400–4000 cm −1 ) on polycrystalline samples, and by polarized Raman spectroscopy (30–3500 cm −1 ) on microcrystals orientated with respect to the organic and inorganic sublattices. The strongly polarized Raman spectra at low wavenumbers are consistent with the existence of orientated [Cu 2 Cl 6 ] 2− bitetrahedra that exhibit a quasi C 2h symmetry. Ab initio calculations using Gaussian 98 set of quantum chemistry code are performed by DFT approach with B3LYP to predict the set of normal modes characteristics of free [Cu 2 Cl 6 ] 2− . The reliability of 3-21G, 6-31G(d) and LanL2DZ basis functions has been first checked in the case of [CuCl 4 ] 2− for which the results can be compared with experimental data previously reported. The low wavenumbers Raman spectra of [N(C 3 H 7 ) 4 ] 2 Cu 2 Cl 6 are analysed and the lines are assigned on the basis of group theory and the ab initio calculation results. The whole vibrational characteristics of the [Cu 2 Cl 6 ] 2− bitetrahedra are given.