TEMPERATURE-DEPENDENT EMISSION PROPERTIES OF RHENIUM(I) TRICARBONYL COMPLEXES CONTAINING ALKYL-SUBSTITUTED AND ARYL-SUBSTITUTED PHENANTHROLINES AS LIGANDS

The results of the temperature dependence in fluid solution of the emi ssion behavior of a series of [Re(L-L)(CO)(3)py](+) complexes (L-L = 3 ,4,7,8-Me(4)phen, 4,7-Ph(2)phen, 2,9-Me(2)-4,7-Ph(2)phen, 4,7-Me(2)phe n, 5,6-Me(2)phen, 5-Phphen, 2,9-Me(2)phen, and phen) are presented alo ng with an interpretation which assigns the lowest excited state as (3 )MLCT, with a contribution from a higher-energy, shorter-lived state o f unknown character. The emission lifetime of [Re(3,4,7,8-Me(4)phen)(C O)(3)py](+) actually increases with temperature, reaches a maximum at approximately 230 K, and then decreases in the usual manner. This beha vior is attributed to population of the lowest (3)LC state, which in t his complex lies just above the 3MLCT emitting state and below the upp er state.