Because the pyridyl group can act as a proton acceptor and a coordination biting unit, electrodes with films of dithiolene complex [n-Bu4N][Ni(4-pedt)2] (1) (4-pedt = 1-(pyridine-4-yl) ethylene-1,2-dithiolate) are prepared to investigate the photocurrent response behaviours of a metal dithiolene compound upon protonation and transition metal coordination. The morphologies of film 1 are characterized by SEM analysis. Photoelectrochemical measurements are carried out with the electrodes of film 1. The results are as follows: (1) the stronger the medium acidity is, the weaker the photocurrent becomes. (2) Photocurrent intensities of Mn(II), Co(II) and Zn(II) treated film 1 are increased in comparison with that of the original film 1 due to the polymeric coordination. (3) When film 1 is treated by Fe(III) ions, it is oxidized to a neutral [Ni(4-pedt)2] film that shows weaker photocurrent response. In addition, a new ionic pair compound MV[Ni(4-pedt)2]2 (2) (MV2+ = methylviologen dication) synthesized by cation exchange shows good photocurrent response properties due to the improvement of electron transfer.
