Etude structurale et vibrationnelle

des monocristaux [(CH3)3NH]2SiF6 et [(C2H5)4N]2SiF6

A. Ouasri1, M. S. D. Elyoubi1, T. Guedira1, A. Rhandour1*, M. Bahri2 , H. Feki3, Y. Abid3

1Laboratoire de Physico-Chimie des MatÚriaux Inorganiques, FacultÚ des Sciences, Kenitra, Maroc

2Laboratoire de Physique Atomique et MolÚculaire, FacultÚ des Sciences de Tunis, Tunisie

3Laboratoire de Physique MolÚculaire et Cristalline, FacultÚ des Sciences, Sfax, Tunisie

* Corresponding author. E-mail : lpcmi@yahoo.fr

Received 13 March 2001; revised version accepted 20 April 2001

Abstract

Single crystals of [(CH3)3NH]2SiF6 and [(C2H5)4N]2SiF6 crystalize at ambient temperature respectively in the centred cubic system (a = 11.688 ┼) and the monoclinic system of space group P21 (a = 13.430 ┼, b = 13.825 ┼, c = 12.940 ┼ et b = 90.8942░). We have attempted an assignement of the infrared spectra of these two compounds based on the litterature data, on theoritical group predictions and on the results of SCF semi empirical calculations of vibrational frequencies. We computed these latters after having calculated the optimal geometry of minimal energy for neutral entities (CH3)3NH-F(SiF4)F-HN(CH3)3 and (C2H5)4N(SiF6)N(C2H5)4. The formation of hydrogen bonding of N-H---F type is only observed for the [(CH3)3NH]2SiF6.

Keywords Hexahalogenometallates; IR Spectroscopy; Molecular Modeling.

ę 2015