Ruthenium polypyridyl complexes that form supramolecular assemblies with halide ions are particularly appealing for fundamental studies of excited-state redox chemistry. As the halide and ruthenium are prearranged before light excitation, diffusion is not required for excited-state quenching. In recent work, ground-state assemblies between ruthenium polypyridyl complexes and halides have been shown to affect halide oxidation. These results have implied that excited-state supramolecular assembly structures are in part responsible for the mechanisms and kinetics of these important energy-storing reactions. In this presentation, control over excited-state supramolecular assembly structures is shown to be achieved through molecular design. Through variation of the substituents on the bipyridyl ligand, the excited-state equilibrium constant (K*eq) for chloride association was tuned relative to the ground-state equilibrium constant (Keq). In particular, the excited-state dipole orientation was utilized to achieve halide photorelease. The rate constants for halide photorelease were determined in organic solution and were found to span an order of magnitude (2.3 to 47 × 105 s-1) depending on the identity of functional groups at the receptor site. These results are discussed in relationship to excited-state electron transfer reactions and applications that involve halide release in polar solvents.

Molecular control over excited-state supramolecular assembly

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.