Tuning Optical Properties of Re(I) Carbonyl Complexes by Modifying Push–Pull Ligands Structure

In this work, the structure–property relationship was investigated for a series of Re(I) carbonyls [ReCl(CO)3(R-terpy-κ2N)], [ReCl(CO)3(R-dtpy-κ2N)], and [ReCl(CO)3(R-dppy-κ2N)]. The studied compounds bear 2,2′:6′,2″-terpyridines (R-terpy), 2,6-di(thiazol-2-yl)pyridines (R-dtpy), and 2,6-di(pyrazin-2-yl)pyridines (R-dppy) functionalized with strongly electron-donating cyclic (piperidine and morpholine) and acyclic (dimethylamine, diphenylamine) amine donor attached to the central pyridine ring of the triimine skeleton via phenylene linkage. Their thermal properties were evaluated using DSC. The ground- and excited-state properties of these systems were elucidated with electrochemistry, absorption and emission spectroscopy, and density-functional theory (DFT)-based calculations. The terpy skeleton was found to efficiently stabilize the LUMO orbital, as manifested by the most negative reduction potentials for Re(I) terpyridine complexes and significant blue-shift of the absorption and emission of [ReCl(CO)3...