OCTAHEDRAL MONOMERIC MOLYBDENUM(III) - A MAGNETOOPTICAL STUDY OF MO-3+ DOPED IN CS2NAYCL6

The first magneto-optical study of the4A2g→2T2g absorption,2Eg →4A2g and2T2g→2Tlg,2Eg luminescences of MoCl63−in Cs2NaYCl6as well as the absorption spectrum of the spin-allowed4T2g and4Tlg ligand field States, are reported. Magneto-optical methods have allowed difficulties in a previous assignment to be resolved. Coupling of almost all electronic origins to alg, t1u and both tlu MoCl63− internal modes, as well as (lu lattice modes, is established, uniquely, from the sign of the magnetic circular dichroism and magnetic circular polarization of luminescence spectra. In addition, coupling to a tlu internal mode of the host YC163“unit is observed. Moderate coupling to the eg JahnTeller mode occurs for the2T2g(U'),2Tlg(U') and2Eg(U') origins, particularly the former, but is very weak or absent for the2T2g(E") and2Tlg(E') origins. A comparison of the relative dipole strengths induced by tlu and t2u vibrations, as well as the sign of the MCPL for the2Eg→4Alg transition, are consistent with the intensity for the4T2g→2Eg,2Tlg,2T2g transitions being borrowed pri- marily from the4T2g state via spin-orbit coupling. The observed2Tlg and2T2gspin-orbit Splittings of 102 and 75 cm-1respectively, are reduced by approx- imately one third from those calculated, and this reduction is attributed to a Jahn-Teller effect. © 1990 Taylor & Francis Group, LLC.