THERMAL REDISTRIBUTION OF ENERGY FROM AN EXCITED (3)PI-PI-ASTERISK TERM TO A NEARBY CHEMICALLY REACTIVE (3)DD LEVEL IN [RH(III)(NN)(3)](PF6)(3) COMPLEXES

Below approximate to 150 K [Rh(NN)(3)](PF6)(3) complexes display (3) p i pi phosphorescences characteristic of the NN diimine ligand [NN = 1 ,10-phenanthroline (phen) or 2,2'-bipyridine (bpy)]. Above approximate to 150 K and below the melting point of glycerol, a temperature-depen dent first-order photoreaction occurs. Temperature dependencies of the se photochemical reactions conform to the Arrhenius equation with acti vation energies in the 2-3 x 10(3) cm(-1) range. These results are int erpreted in terms of thermal redistribution from an excited (3) pi pi term to a nearby chemically reactive (3)dd manifold. The relationship of the Arrhenius activation energies to the electronic states of the parent complexes and the paths of intramolecular energy migration are discussed.