Abstract

The electrochemical and photochemical properties of the rhenium complexes Re(CO)3Cl(phendione) and Re(CO)3Cl(AQphen) (phendione = 1,10-phenanthroline-5,6-dione; AQphen = naphtho[2,3-h]dipyrido[3,2-a:2?,3?-c]phenazine-8,13-dione) were investigated for their potential in CO2 capture. UV-vis spectra in dimethyl sulfoxide (DMSO) showed absorption maxima at 370 and 391 nm, attributed to metal-to-ligand charge transfer (MLCT) transitions, as confirmed by time-dependent density functional theory (TD-DFT) calculations. Electrochemical studies revealed two one-electron reduction events: ?0.12 and ?0.77 V for Re(CO)3Cl(phendione) and ?0.30 and ?0.79 V for Re(CO)3Cl(AQphen) (vs Ag/AgCl). In the presence of CO2, the second reduction shifted positively by 0.20 and 0.14 V, indicating adduct formation. Association constants (log K) were 5.4 and 3.9 for phendione and AQphen derivatives, respectively. DFT calculations supported formation of [quinone-CO2]2- adducts, with bond lengths of 1.447 and 1.406 Å. Under blue LED light (410 nm) and CO2, photochemical experiments showed spectral changes consistent with reduced quinone-CO2 species. These results highlight the ability of rhenium-quinone complexes to engage in electrochemical and photochemical CO2 capture, offering insights into their charge transfer properties and CO2 binding behavior. © 2025 American Chemical Society.