A Heterobimetallic Au~Ⅲ-Pt~Ⅱ Photocatalyst For Water Reduction To Hydrogen

Hydrogen is considered to be a preferred alternative to fossil fuels due to its extremely high energy-density/mass ratio.One of the most promising environmentally friendly and sustainable methods to produce hydrogen is artificial photosynthesis,which directly converts solar energy into chemical energy of H2.Most of the homogeneous photocatalytic systems have higher turnover number,and prevail in mechanism research and structure tuning compared with heterogeneous ones.An ideal supramolecular photocatalytic system could replace the intermolecular electron transport process of traditional multi-component systems by vectorial intramolecular electron transfer,so that the catalytic center would obtain energy from sensitizer unit.The photoinduced intramolecular electron migration character of supramolecular structure has been applied in the field of photocatalysis.In this paper we designed and systhesized a heterobimetallic complex(1)composed of cyclometalated alkyne gold photoactive fragment,central phenylethynyl bridging group and platinum terpyridine catalytic unit,and four references:mononuclear(2)and binuclear(4)gold compounds based on cyclometalated alkyne;mononuclear(3)and dinuclear(5)platinum compounds based on terpyridine.Their photophysical,photoredox chemistry,electrochemistry properties were characterized by UV-vis absorption spectra,emission spectra and cyclic voltammetry.DFT and timedependent(TD)-DFT calculations were carried out in light of their geometry and electronic structure.The results showed that electronic communications between the two metallic centers via the bridge ligand enhanced the absorptivity in the visible region of heterobimetallic complex(1).Intramolecular electron and energy transfer occurred.Complex(1)could be reductive quenched and be used as photocatalyst in water reduction.The dissertation emphasized to research the photocatalytic hydrogen evolution performance of heterobimetallic gold-platinum complex(1)in water/acetone mixed solvent.It was found that the supramolecular system consisting of the Au-Pt assembly(1)expressed better photocatalytic activity than the related three-component system,since the intramolecular electron tranfer between sensitizer unit and catalytic unit is more efficient.The supramolecular system was optimized and the turnover number of the whole system reached 91 in acetone/water(1/1,v/v)with ascorbic acid as sacrificial agent under irradiation with visible light for 12 hours.