The single-crystal spectrum of transitions to 1G states of nickel(II) in distorted tetrahedral environments

Abstract

Temperature-dependent and polarized spectra of transitions to excited states arising from the ¹G free-ion term are reported for single crystals of (Et₄N)₂NiCl₄ and (Et₄N)₂NiBr₄. The resolved fine structure of one band at 5 K is interpreted in terms of progressions in the symmetric modes. The results suggest that these hitherto unutilized bands could be of importance in establishing the nature of the co-ordination of nickel ions in less exactly defined environments, and they are used here to give some insight into the change in geometry of the NiCl₄^2– and NiBr₄^2– units as the temperature is lowered.