Photochromic Substitution and Electron-Transfer Reactions of the Transition metal Complexes

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It is an attractive approach to construct a new photoreaction system in connection with the light-triggered molecular devices. We recently reported the photochemical substitution reactions of the ruthenium(II) complexes containing tetradentate Schiff base ligands. In this work, we report the bidirectional photo and thermal substitution reactions of ruthenium(II) complexes containing Schiff base ligands.The tridentate Schiff base ligands were prepared by the reaction of 2-diphenylphosphinobenzaldehyde and 2-hydroxyethylamine or its derivative in ethanol. Equimolecular quantities of [RuClィイD22ィエD2(PPhィイD23ィエD2)ィイD23ィエD2] and ppb-etol (N-(2-diphenyl-phosphinobenzilidene)-2-hydroxyethylamine) were dissolved in dichloromethane and refluxed for 8 h. Red-orange crystals of [RuClィイD22ィエD2(ppb-etol)(PPhィイD23ィエD2)ィイD23ィエD2] (1) were obtained from a dichloro-methane-hexane solution. In acetonitrile, the chrolo ligands of complex 1 are substituted with the solvent molecules to yield an equilibrium mixture of [RuClィイD22ィエD2(CHィイD23ィエD2CN)(ppb-etol)(PPhィイD23ィエD2)ィイD23ィエD2]Cl (2) and [RuClィイD22ィエD2(CHィイD23ィエD2CN)(ppb-etol)(PPhィイD23ィエD2)ィイD23ィエD2]ClィイD22ィエD2 (3) at 50℃ in the dark. The reaction is accompanied by a color of the solution reverts to orange, and complexes 2 and 3 are converted again into complex 1. The color change can be made repeatedly and a reversible photochromic reaction system is constructed.We also reported about the structures and reactives of the pentadentate Schiff base-ruthenium (II) complexes.