Oxidation Of Organic Substrates With Water As An Oxygen Source

Artificial photosynthesis system plays an crucial role in solar energy conversion into clean and renewable fuel. With this respect, development of photoelectrochemical (PEC) cells based on artificial photosynthesis system is a promising approach for sunlight transfer to hydrogen. In principle, both water and organic substrates are available fuels for such devices. Although much effort has been devoted to photo-induced water oxidation, photo-induced organic substrates oxidation using molecular catalyst is relatively rare. Narrow substrate scope as well as low selectivity and conversion are main drawbacks for practical application of this photocatalysis system in viable PEC cells.To develop efficient photocatalytic hydrocarbon oxidation system, in this research, three ruthenium complexes [Ru(dmp)2(H2O)2](PF6)2 (Rul, dmp= 2,9-dimethyl-1,10-phenanthroline),[Ru(tpy)(bpy)(OH2)](ClO4)2 (Ru2, tpy= 2,2',6',2"-terpyridine, bpy= 2,2'-bipyridine) and Ru(pda)(mpy)(bpy) (Ru3, pda= 2,6-pyridinedicarboxylic acid, mpy= 4-picoline) were prepared and characterized. Their catalytic properties on alkene's selective oxidation were investigated by using Ce(NH4)2(NO3)6 (CeⅣ) as an oxidant and water as an oxygen source. Our results showed that Rul and Ru2 could catalytically oxidize various alkenes with highly selectivities. It was also found that Rul and Ru2 are higly efficient catalysts in a three components homogeneous photocatalysis system consisting of photosensitizer,.sacrificial electron acceptor and catalyst. In particular, remarkable yield and 100%selectivity were obtained in the conversion of sulfide to sulfoxide. Cyclic voltammetry and UV-Vis spectrometry reveals the possible catalytic active species in photocatalysis system is high-valent metal-oxo intermediate.Nonprecious metal cataylsts including manganese catalysts Mn(dmp)2(CF3SO3)2 (Mnl), Mn(bpy)2(CF3SO3)2 (Mn2) and Q3Mn(HQ= 5-C1-7-I-8-OH-quinoline, Mn3) and iron cayalysts Fe(pda)(imz)3 (Fel, pda= 2,6-Pyridine dicarboxylic acid, imz= imidazole), [((phen)2(H20)FeⅢ)2(μ-O)](C104)4 (Fe2) and [Fe(dmp)2(H2O)2] (CF3SO3)2 (Fe3) were prepared as a replacement for ruthenium based catalysts. Their catalytic properties with water as an oxidant were studied, which show an inferior catalysis capability in comparison with the ruthenium complexes.