High temperature infrared spectra and vibrational analysis of GaBr3 and AlBr3NH3 in the vapour phase

Abstract

Abstract The i.r. vapour spectra of monomeric and dimeric gallium bromide and of tribromoammine aluminium at 523–723 K were recorded in the 50–1800 and 2300–3500 cm−1 regions. An evacuable nickel cell equipped with a type IIa diamond window and sealed with a gold O-ring was employed. With the exception of the dimer ring puckering, all i.r. active gallium bromide fundamentals were observed. The monomer spectra were found to be consistent with a planar D3h structure. All i.r. active modes of tribromoammine aluminium, except the symmetric NH stretch and AlBr3 rock vibrations, were assigned. The interpretation was supported by normal coordinate analyses. An attempt was made to correlate the valence stretching force constants of several MX3, M2X6, M2X−7 (M = Al, Ga; X  Cl, Br, I) compounds with the MX bond lengths.