Complete Ag4M2(DMSA)4 (M = Ni, Pd, Pt, DMSA = Dimercaptosuccinic Acid) Cluster Series: Optical Properties, Stability, and Structural Characterization.

The cluster series Ag4M2(DMSA)4 (M = Ni, Pd, Pt) has been synthesized and the optical spectra and stability have been examined as a function of the metal, M. We have also obtained the structure of Ag4Ni2(DMSA)4 using X-ray crystallography, confirming the previously calculated structure. In the optical spectrum, there is a significant blue shift as the substituted metal M progresses down the periodic table. Theoretical calculations suggest that the blue shift is due to the lowering in energy of the d orbitals of the transition metal, M; however the expected metal-metal excitations are optically weak, and the spectra are dominated by metal-ligand excitations. The Ag4Pd2(DMSA)4 species has exceptionally high stability relative to the previously reported Ni and Pt analogues.