ELECTRONIC-SPECTRA AND PHOTOPHYSICS OF PLATINUM(II) COMPLEXES WITH ALPHA-DIIMINE LIGANDS - SOLID-STATE EFFECTS .2. METAL-METAL INTERACTION IN DOUBLE SALTS AND LINEAR-CHAINS

Solid-state luminescence and absorption data are reported for linear-chain compounds of Pt(II) complexes containing alpha-diimine ligands in combination with CN- and amine ligands. Both neutral (e.g. Pt(bpy)(CN)2) and double-salt (e.g. [Pt(bpy)2][Pt(CN)4]) compounds are examined and compared. All of these compounds have d(Pt2) near 3.3 angstrom, and all exhibit strong electronic emission with lambda-max = 560-715 nm and k(rad) = 10(5)-10(6) s-1. This emission is attributed to a d-sigma*(d(z)2(Pt)) --> pi*(alpha-diimine) triplet-parentage excited state. The assignment is based primarily upon the observed vibronic structure, but correlation with d(Pt2) is also considered. The factors involved in red-shifting this particular type of metal-to-ligand charge-transfer transition relative to the monomer are discussed, as are criteria for distinguishing metal-metal, charge-transfer, and ligand-localized electronic transitions in Pt(II) alpha-diimine complexes.