Electrosynthesis of dixanthylene photochromic dye, characterization and ab initio calculations

The feasibility of electrosynthesis of dixanthylene photochromic dye by electrochemical reduction of xanthone in the presence of perchloric acid has been investigated in acetonitrile at glassy carbon electrode. The electrode shows a remarkable electrocatalytic effect for the reduction of xanthone. Reduction of xanthone at such an electrode occurs at potentials −0.8 V relative to the SCE. The electric charge passed corresponded to 1 electron/molecule relative to the amount of substrate in the electrolysis. In all cases fairly good yields of dixanthylinum perchlorate (95%) was obtained in acetonitrile. The products were analyzed by MS, IR and NMR spectroscopies. The mechanism of electro-reduction is discussed. The photochromic properties of dixanthylinum were studied by conductometric method, UV–vis, and NMR spectra. The optimized geometries were calculated by using restricted/unrestricted Hartree–Fock (RHF/UHF) with 6-31G basis set. Some molecular and spectroscopic properties have also been calculated at the same level of theory and the same basis set for the optimized structures.