Structure and Luminescent Properties of Tellurium(IV) Bromide Complex with p-Toluidinium (HPT)<sub>2</sub>TeBr<sub>6</sub> · H<sub>2</sub>O

Abstract

A complex of tellurium(IV) bromide with p-toluidinium, (HPT)2TeBr6·H2O, was synthesized, its crystal structure was determined by X-ray diffraction, and its absorption and luminescent properties were studied. A comparative study of the luminescent properties at 77 K was performed for a number of tellurium(IV) bromide complexes with outer-sphere cations: cesium, rubidium, tetraethylammonium, and p-toluidinium. The electronic and geometric aspects determining the absorption and luminescent properties of the tellurium(IV) bromide complexes are considered. At 77 K, (HPT)2TeBr6·H2O is characterized by luminescence in the near-IR range; the luminescence band maximum is significantly red-shifted (50 nm) with respect to those of the analogues. The luminescence intensity of complex compounds is influenced by the geometric structure (type of anionic sublattice and the structure and degree of distortion of the coordination polyhedron of the s2-ion). The coordination polyhedron distortion and the presence of a dense system of hydrogen bonds account for the minimum luminescence intensity of the (HPT)2TeBr6·H2O complex among other tellurium(IV) bromide compounds.