We describe the emission spectral properties of two rhenium metal-ligand complexes with one and two-photon excitation, Re(bpy)2(CO)3Cl and [Re(bpy)(CO)3CH3CN]+, where bpy is 2,2’-bipyridyl and CH3CN is acetonitrile. Similar emission spectra and intensity decay times characteristic of the metal-to-ligand charge transfer state were observed for one- and two-photon excitation. The lifetime and quantum yield of the acetonitrile complex are approximately 14-fold higher than that of the chloride complex. Both complexes display high anisotropies near 0.33 in frozen solution with one-photon excitation. Two-photon excitation results in anisotropies about 40% larger, consistent with the increased photoselection expected for two-photon absorption. These complexes display single rotational correlation times in glycerol, but the correlation time of the charged acetonitrile complex is 3 to 4-fold larger. These results show that rhenium complexes can be used as hydrodynamic probes with one- or two-photon excitation.
Copyright © 1999 Elsevier. This article first appeared in Journal of Photochemistry and Photobiology A: Chemistry 122 (1999), 95-101.
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Lakowicz, Joseph R., Felix N. Castellano, Ignacy Gryczynski, Zygmunt Gryczynski, and Jonathan D. Dattelbaum. "Two-photon Excitation of Rhenium Metal–ligand Complexes." Journal of Photochemistry and Photobiology A: Chemistry 122, no. 2 (1999): 95-101. doi:10.1016/S1010-6030(99)00013-1.