PHOTOLUMINESCENCE STUDIES OF LANTHANIDE ION COMPLEXES OF GOLD AND SILVER DICYANIDES .2. A NEW LOW-DIMENSIONAL SOLID-STATE CLASS FOR NONRADIATIVE EXCITED-STATE ENERGY-TRANSFER

The excited state properties of the layered compounds Dy[Au(CN)(2)](3), [DyAu], Gd[Au(CN)(2)](3), [GdAu], and Dy [Ag(CN)(2)](3), [DyAg], have been examined. The donor Au(CN)2- ion both in [DyAu] and [GdAu] systems show a strong and structured emission at low temperatures. Due to the lack of donor-acceptor spectral overlap, energy transfer in the [DyAu] system in inefficient, and thus, emission arising from the acceptor Dy3+ ion is weak at ah temperatures. Similarly, no emission has been observed from the Gd3+ ion as the lowest excited state in the acceptor ion is situated at a much higher energy position than the donor level. From the resonance Raman studies, the structure in the luminescence spectrum of the [DyAu] compound has been assigned to the Au-C symmetric stretching mode and other Raman active modes. Emission from the donor Ag(CN)(2)(-) ion in the [DyAg] system is totally quenched at all temperatures whereas the acceptor Dy3+ ion emits strongly. The rare earth emission intensity in the [DyAg] system increases with a temperature increase, indicating an efficient energy transfer from the donor Ag(CN)(2)(-) to the Dy3+ ion. The (4)G(11/2) excited state of the Dy3+ ion is suggested as the principal acceptor state. An exchange mechanism originating from the overlap of the N atoms of the CN- ligands and the lanthanide, Dy3+ ion, is suggested as the dominant mechanism for the energy transfer process.