EXCITED-STATE ACID-BASE CHEMISTRY OF (ALPHA-DIIMINE)CYANOTRICARBONYLRHENIUM(I) COMPLEXES

The excited-state acid-base photophysics of rhenium(I) complexes of the form LRe1(CO)3CN (L = 1,10-phenanthroline, 2,2'-bipyridine, and 4,7-dimethyl-1,10-phenanthroline) was investigated. The emitting state can be tuned from a metal-to-ligand charge-transfer type to pi-pi* phosphorescence by varying the acidity, L, and temperature. This alteration of excited-state type results in large changes in emission spectra and lifetimes, which suggest use as environmental probes. In low-temperature glasses, site heterogeneity must be invoked to account for the luminescence decay data.