PHOTOLUMINESCENCE STUDIES OF LANTHANIDE ION COMPLEXES OF GOLD AND SILVER DICYANIDES - A NEW LOW-DIMENSIONAL SOLID-STATE CLASS FOR NONRADIATIVE EXCITED-STATE ENERGY-TRANSFER

The excited-state properties of the layered compounds M[Au(CN)2]3 and M[Ag(CN)2]3 (with M = Eu3+) have been examined. Exclusive excitation of the host ions Au(CN)2- and Ag(CN)2- leads to photoluminescence (PL) from the Eu3+ ion, indicating host to guest excited-state energy transfer. The donor Au(CN)2- and Ag(CN)2-emissions are totally quenched at all temperatures. The emission intensity from Eu[Ag(CN)2]3, [EuAg], increases with a temperature increase while the intensity for Eu[Au(CN)2]3, [EuAu], decreases. High-resolution PL data obtained at 78 K indicate that the Eu3+ ion occupies a single site in [EuAg], while multiple-site occupations are indicated in [EuAu]. The covalent Au-Au and Ag-Ag interactions in the two compounds are analyzed by comparing the splittings in the 5D0 --> 7F1 transitions of Eu3+ as well as the intensity ratios of the electric dipole (5D0 --> 7F2) and the magnetic dipole (5D0 --> 7F1) transitions.