1,10-Phenanthroline-dithiine iridium and ruthenium complexes: synthesis, characterization and photocatalytic dihydrogen evolution.

We report the synthesis and the spectroscopic and electrochemical properties of six mononuclear iridium(iii) and ruthenium(ii) complexes bearing S,S'-extended phenanthroline ligands. Starting from 5,6-dibromide-1,10-phenanthroline, the dithiine derivatives N,N'-1,10-phenanthrolinedithiino[2,3-b]quinoxaline and N,N'-1,10-phenanthrolinedithiino[2,3-b]benzene were prepared by primary N,N'-complexation of the dibromo derivative and subsequent nucleophilic substitution at the complex. The photoluminescence of the phenanthroline-dithiine containing complexes shows distinctively increased lifetimes for all Ir(iii) and Ru(ii) complexes. The activity of the series of Ir(iii) and Ru(ii) complexes as photosensitizers in visible-light photocatalytic water reduction is demonstrated by dihydrogen evolution with a [Fe3(CO)12] catalyst and triethylamine as a sacrificial donor.