One-Step versus Two-Step Valence Tautomeric Transitions in Tetraoxolene-Bridged Dinuclear Cobalt Compounds
Jia-Ping Wang, Wen-Ting Liu, Meng Yu, Xue-Yang Ji, Jing-Lin Liu, Manzhou Chi, Alyona A. Starikova, Jun Tao
Abstract
The syntheses of valence tautomeric compounds with multistep transitions using new redox-active ligands are the long-term goal of the field of bistable materials. The redox-active tetraoxolene ligand, 2,7-di-tert-butylpyrene-4,5,9,10-tetraone (pyreneQ–Q), is now developed to synthesize a pair of dinuclear compounds {[CoL2]2(pyreneSq–Sq)}[Co(CO)4]2·xCH2Cl2·2C6H5CH3 (1, x = 2, L = 1,10-phenanthroline, phen; 2, x = 1.5, L = 2,2′-bipyridine, bpy). Variable-temperature magnetic susceptibilities and single-crystal X-ray diffraction measurements indicate a partial one-step valence tautomeric transition for 1 and a rare two-step valence tautomeric transition for 2, respectively. DFT calculation results are consistent with the experimental data, revealing the correlation between thermodynamic parameters and the one-step/two-step valence tautomeric behaviors.