Synthesis, structure, and dynamics of mixed-ligand cobalt complexes with redox-active phenoxazin-1-one

Abstract

155 Considerable interest in studying the structure and dynamics of bistable transition metal complexes with redox active (non innocent) ligands stems from the possibility to design quick response magnetically active molecular switches and energy independent molecular memory [1–3]. The mechanism of ther mally or photochemically controlled rearrangements of such complexes (redox isomerism or valence tau tomerism) is determined by intramolecular electron transfer between energetically closely spaced d orbitals of the central atom and the frontier orbitals of the ligand. In the most general way, these conditions are achieved in hexacoordinated d4–d7 metal complexes with sterically protected о quinone or о quinone imine ligands in different oxidation states in which the coordinative saturation of the central ion is ensured by introducing a neutral bidentate ligand [4, 5]. Another approach to the synthesis of potentially valence tautomeric metal complexes, used in the present work, involves the interaction of a stable tetra coordinated metal complex with a bidentate redox active ligand. Previously, mixed ligand bis(acetylacet onato)ruthenium complexes with о iminoquinone, о iminothioquinone, and о diiminoquinones (1a) were synthesized [6, 7]. With the ligands of the last type, chromium complexes (1b) have been recently obtained [8]. Adducts of о quinone and phenan threnequinone with Fe(salen) (2) are known [9].