Photoinduced hydrogen evolution with peptide dendrimer-multi-Zn(II)-porphyrin, viologen, and hydrogenase

To construct an artificial photosynthetic system, multi-Zn(II)-mesoporphyri ns in peptide dendrimers were equipped as a photosensitizer of photoinduced hydrogen evolution in a four-component system (electron donor, photosensit izer, electron carrier, and catalyst), so that hydrogen was evolved effecti vely by the dendrimer architecture, for the first time. The hydrogen evolut ion activity was correlated to the photoreduction ability of viologen by th e Zn-porophyrin-peptide dendrimers. Additionally, using positively charged methyl-viologen as an electron carrier, the photoinduced hydrogen evolution function with the positively charged peptide dendrimer was superior to tha t with the negatively charged peptide dendrimer, despite that the positive dendrimer did not strongly bind the positively charged methyl-viologen with the electrostatic interaction. By contrast, when zwitterionic propylviolog en sulfonate was used, photoreduction and hydrogen evolution properties wer e identical between the positively and the negatively charged dendrimers. T hese results demonstrated that the dynamic interaction between the positive dendrimer and methyl-viologen was preferable for the photoreduction and hy drogen evolution, and that the three-dimensional assembly of Zn(II)-mesopor phyrins using the peptide dendrimers was effective as a photosynthesis. (C) 2001 John Wiley & Sons, Inc.