Homogeneous catalysis of platinum(II) complexes in photochemical hydrogen production from water

This review concentrates on the Pt(II)-catalyzed reduction of water into molecular hydrogen, with emphasis given to the works undertaken thus far by the authors' group. The homogeneous catalysis of (i) dinuclear platinum(II) complexes, (ii) mononuclear platinum(II) complexes, (iii) platinum(II) complexes having electron-acceptor groups, and (iv) platinum(II) complexes having photosensitizing groups is described. The dependences of the H₂-evolving activity on the metal-metal interaction, the Pt(II) d_z2 orbital energy, the steric factor, and the electron-acceptor ability are discussed. Moreover, the first active model of a photo-hydrogen-evolving molecular device made up of a tris(2,2′-bipyridine)ruthenium(II) derivative and a homogeneous platinum(II) catalyst is discussed.