Synthesis and photophysical investigation of supramolecular complexes developed for photoinitiated electron collection

In this research, photochemical molecular devices were designed to perform photoinitiated electron collection. These devices were synthesized, characterized and their spectroscopic, photochemical and electrochemical properties investigated. The general formula for these systems is {[(bpy)₂Ru(BL)]₂MCl₂}⁵⁺ (M = Ir^III and BL = dpq (2,3-bis(2- pyridyl)quinoxaline) or dpb (2,3-bis(2-pyridyl)benzoquinoxaline), or M = Rh^III, BL = dpp (2,3-bis(2-pyridyl)pyrazine)). The functioning of these devices as photoinitiated electron collectors was determined. Through the use of a sacrificial electron donor in a photolysis experiment, the functioning of the {[(bpy)₂Ru(dpb)]₂IrCl₂}⁵⁺ trimetallic complex as a photochemical molecular device for photoinitiated electron collection was established. The interaction of the electron donor with the trimetallic complex was also investigated through a Stern-Volmer quenching study.

To tune the properties of the chromophoric units, [Ru₂(bpy)(BL)]²⁺, the bridging ligand was varied. The dpq bridging ligand was modified through the incorporation of electron donating and electron withdrawing substituents. The 6,7-dimethyl-2,3-bis(2’- pyridyl)quinoxaline and 6,7-chloro-2,3-bis(2’-pyridyl)quinoxaline bridging ligands were synthesized and characterized. The ruthenium mono- and bimetallic complexes utilizing these bridging ligands, as well as dpb, were synthesized and investigated. It was shown that the light absorbing and electrochemical properties of these [Ru(bpy)₂(BL)]²⁺ chromophores can be varied by altering the π-acceptor nature of the bridging ligand.