Electropolymerization and characterization of terpyridinyl iron (II) and ruthenium (II) complexes

Abstract

Abstract Electroactive 2,2′: 6,2″‐terpyridinyl ligands ( 3, 5, 6 ) and their iron(II) ( 7a–9a ) and ruthenium(II) complexes ( 7b–9b ) were synthesized. Bis[3‐(aminophenyl)‐2,2′ :6,2″‐terpyridinyl]metal(II) complexes ( 7a, 7b ) and bis[2‐(hydroxyphenyl)‐2,2′ :6,2″‐terpyridinyl]metal(II) complexes ( 8a, 8b ) were electropolymerized on to the surface of Pt or In‐SnO 2 (ITO) electrodes in acetonitrile containing Bu 4 NCIO 4 by scanning the potential between O and + 1.6V (for 7a and 7b ), and −0.8 and +1.6V (for 8a and 8b ) versus saturated calomel electrode. The electrodes obtained by electropolymerization exhibited reversible electrochromism based on Fe(II)/Fe(III) or Ru(II)/Ru(III) redox couple. Photoresponses to visible light were found in the modified electrode obtained by electropolymerization of ruthenium complex 7b in an aqueous LiClO 4 solution containing methylviologen (cation MV 2+ ) under an O 2 atmosphere. The mechanism for the photoresponded cathodic current was explained in terms of an excitation of bis(terpyridinyl)ruthenium(II) complex [Ru(terpy) 2 2 + ] by visible light, an electron transfer from the excited state [Ru(terpy) 2+* 2 ] to MV 2+ , reduction of Ru(terpy) 3+ 2 at an electrode, and oxidation of MV +* with O 2 .