The voltammetric reduction, deprotonation and surface activity of ruthenium photovoltaic sensitizers in acetone

The reductive voltammetry of the photovoltaic sensitizer [(H-2-dcbPY)(2)Ru( NCS)(2)] (H-2-dcbpy = 2,2 ' -bipyridine-4,4 ' -dicarboxylic acid) and [(H-3 -tctpy)Ru(NCS)(3)](-) (H-3-tctpy=2,2 ' :6 ' ,2 " -terpyridine-4,4 ' ,4 " -t ricarboxylic acid) has been investigated in acetone. Significant surface in teractions at both platinum and glassy carbon electrodes occur at 0.6 V pri or to the reversible potential expected for ligand-based reduction process of the fully protonated acids. The origin of the surface interactions are a ttributed to the acid-base behaviour of the compounds, combined with overal l deprotonation and reduction to hydrogen, since repetitive cycling of the potential reveals well-defined reversible reduction processes in the negati ve potential range, resulting from formation of doubly deprotonated [(H-dcb py(-))(2)Ru(NCS)(2)](2-) and singly deprotonated [(H-2-tctpy(-))Ru(NCS)(3)] (2-), respectively. The extent of the surface interactions has been estimat ed by electrochemical quartz crystal microbalance and chronocoulometric mea surements. Under certain conditions, a thick conducting polymer consisting of several hundred monolayers is formed. (C) 2001 Elsevier Science B.V. All rights reserved.