Mixed Valence Creutz−Taube Ion Analogues Incorporating Thiacrowns: Synthesis, Structure, Physical Properties, and Computational Studies

Abstract

A series of nine new complexes incorporating [Ru(II)Cl([n]aneS(3))] (n = 12, 14, 16) metal centers bridged by three ditopic ligands containing two monodentate sites (pyrazine, 4,4'-bipyridine, and 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine) have been synthesized and fully characterized. The solid-state structures of three of the complexes have been further characterized by X-ray crystallography studies. Intermetallic interactions within the new systems have been probed using electrochemistry and optical spectroscopy. Cyclic voltammetry reveals that the three pyrazine bridged systems display two separate Ru(III)/(II) redox couples. Using spectroelectrochemistry, we have investigated the optical properties of these mixed valence, Creutz-Taube ion analogues. An analysis of the intervalence charge transfer bands for the complexes revealed that, despite possessing the same donor sets, the electronic delocalization within these systems is modulated by the nature of the coordinated thiacrown. Computational modeling using density function theory offers further evidence of interaction between metal centers and provides insights into how these interactions are mediated.