RUTHENIUM(II) COMPLEXES OF A FUSED PHENANTHROLINE-PTERIDINEDIONE LIGAND

A new alloxazine ligand, produced by the condensation of 1,10-phenanthroline-5,6-dione with 5,6-diamino-1,3-dimethyluracil (1; ''Pptd'') and three ruthenium(II) polypyridyl complexes containing this ligand, [(bpy)3-ninfinityRu(II)(Pptd)n](PF6)2.nH2O, have been synthesized. Pptd is a flavin isomer and is thus capable of proton-coupled reductions in aqueous solutions at glassy carbon electrodes. 'Clustering'' of these Pptd ligands around a Ru(II) center produces stable ruthenium(II) polypyridyl complexes which are in principle capable of being reduced by up to six H atoms (making them potential electrochemical mediators). The synthesis and characterization of the ligand and complexes are discussed. In addition, preliminary data on the pH-dependent reduction (in aqueous solution) of Pptd coordinated to Ru(II) in [(bpy)2Ru(II)(Pptd)]2+ are presented.