Re(I) diimine tricarbonyl complexes are ubiquitous for their energetically tunable metal-to-ligand charge transfer (MLCT) excited states. Many applications of these chromophores rely upon attaining a long-lived excited state suitable for facilitating bimolecular chemical reactions in solution. To that end, the rapid nonradiative decay channels largely governed by the presence of three high frequency CO ligands needs to be overcome. The analogous Re(I) dicarbonyl complexes reduce the number of modes while lowering the frequencies of the remaining CO ligand vibrations since ?-backbonding now becomes distributed between two CO’s instead of three. In this work, a comprehensive series of Re(I) diimine dicarbonyl complexes of the general molecular formula cis-[Re(N^N)2CO2]+ were prepared and studied to systematically evaluate the photophysical consequences of various substituents resident on the diimine ligands (N^N = 2,2’-bipyridine and 1,10-phenanthroline derivatives). These panchromatic chromophores were structurally characterized, evaluated for their electrochemical and spectroelectrochemical properties, and finally investigated using static and dynamic photoluminescence, absorbance, and infrared spectroscopy from ultrafast to supra-nanosecond time scales. This presentation will detail these combined experimental results and reports on the ultrafast dynamics of this class of molecules for the first time using both electronic and vibrational spectroscopy. The MLCT excited state decay of these dicarbonyl molecules appears completely consistent with energy gap law behavior and the reduction in the number of CO subunits attenuates nonradiative decay with respect to the tricarbonyl analogs.

Photophysical properties of rhenium(i) diimine dicarbonyl complexes containing phenanthroline and bipyridine ligands

2019 Fall National Meeting

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