Abstract

Significant advances have been made in the design and characterization of molecular assemblies which, upon photoexcitation, undergo intramolecular electron or energy transfer.¹ These reactions have typically been followed by transient electronic absorption spectroscopy. This technique, however, suffers from the disadvantage that absorption bands tend to be broad and featureless which can lead to ambiguous interpretation in complex assemblies, especially where there is more than one absorbing chromophore. Time-resolved resonance Raman spectroscopy has been applied to the study of excited states,² but time-resolved infrared spectroscopy (TRIR) is particularly well-suited to probing complexes containing ligands such as CO or CN which are bound to the metal.³ Unlike the transient Raman experiment, TRIR does not rely on resonance enhancement in the excited state since the metal-CO and -CN stretching vibrations have large oscillator strength providing high sensitivity. We describe here a novel application of TRIR spectroscopy to the elucidation of intramolecular energy transfer in the ligand-bridged complex, [(phen)(CO)₃Re^I(NC)Ru^II(CN)(bpy)2]⁺ (phen is 1,10-phenanthroline, bpy is 2,2'-bipyridine),⁴ representing the first application of the technique to a process of this type.

© 1992 The Author(s)