Design of Ruthenium Biimidazole-Anthraquinone Dyads to Demonstrate Photoinduced Electron Transfer: Combined Experimental and DFT/TD-DFT Investigations

Abstract

A Biimidazole-anthraquinone ligand has been utilized in this paper to synthesize a new family of Ru(II) complexes capable of demonstrating intramolecular electron transfer from excited *[Ru(ppy)]2+ fragment to the 9,10-anthraquinone moiety upon excitation at their MLCT bands. The electronic properties of the dyads were fine-tuned by varying the coligand in the complexes. All the complexes were thoroughly characterized by standard analytical tools and spectroscopic techniques. X-ray crystal structure of a representative complex (2) was also been determined and found to crystallize in the monoclinic space group P-1. An attempt was made to assess detailed energetics and the rates of photoinduced intramolecular electron transfer in the complexes. Finally, computation works employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were also carried out to investigate the electronic structures of the complexes as well as proper assignment of experimentally observed photo-redox behaviors.