Luminescence and thermochromic properties of complexes of tellurium(IV) halides with rubidium Rb$_{2}$TeHal$_{6}$ (Hal = Cl, Br, I)

Spectral-luminescence properties of complex compounds of the composition Rb$_{2}$TeHal$_{6}$ (Hal = Cl, Br, I) have been investigated. The dependence of the luminescence intensity on the geometric structure of the tellurium(IV) coordination polyhedron of the anion sublattice type and the position of the $A$-band in the spectra has been revealed. Rb$_{2}$TeCl$_{6}$ has exhibited the maximum luminescence intensity at 77 and 300 K for isle-like octahedral coordination of the Te(IV) ion. Rb$_{2}$TeCl$_{6}$ and Cs$_{2}$TeBr$_{6}$ have demonstrated a reversible thermochromism determined by the temperature dependence of the Jahn–Teller splitting of the $A$-band in the absorption (reflection) spectra of the tellurium(IV) ion.