Synthesis and enhanced photosensitization ability of a 4-carboxy-2,2′:6′,2′′-terpyridine complex of ruthenium(II)

• Published in: Polyhedron 2002-01, Vol.21 (1), p.49-54
• Main Authors: Mikel, Charles, Potvin, Pierre G
• Format: Article
• Language: English
• Subjects: 2,2′:6′,2′′-Terpyridine; 4′- p-Tolyl-2,2′:6′,2′′-terpyridine-4-carboxylic acid; Cyclic voltammetry; Photoinduced electron transfer; Ruthenium(II) complexes; Supramolecular pre-association
• ISSN: 0277-5387
• DOI: 10.1016/S0277-5387(01)00959-7

The new ligand 4-carboxy-4′- p-tolyl-2,2′:6′,2′′-terpyridine (HttpyA) was prepared in complexed form via the methyl ester (ttpyE), which was elaborated from methyl isonicotinate in two-steps and in good yields. The homoleptic complex [Ru(ttpyE) 2](PF 6) 2 was prepared, characterized, and hydrolyzed to produce the diacid complex, H 2[Ru(ttpyA) 2] 2+. Once ionized to the neutral [Ru(ttpyA) 2] 0, there are no long-range electrostatic repulsions with the electron acceptor methyl viologen (MV 2+), and the surface COO − groups are suitably disposed for a close-range, 1:1 supramolecular pre-association with MV 2+. H 2[Ru(ttpyA) 2] 2+ was indeed a significantly better photosensitizer in effecting electron transfer to MV 2+ in CH 3CN than was the non-carboxylated dicationic analogue, Ru(ttpy) 2 2+ (ttpy is 4′- p-tolyl-2,2′:6′,2′′-terpyridine). The new ligand 4-carboxy-4′- p-tolyl-2,2′:6′,2′′-terpyridine (HttpyA) was prepared in complexed form via the methyl ester (ttpyE), which was elaborated from methyl isonicotinate in two-steps and in good yields. The homoleptic complex [Ru(ttpyE) 2](PF 6) 2 was prepared, characterized, and hydrolyzed to produce the diacid complex, H 2[Ru(ttpyA) 2] 2+. Once ionized to the neutral [Ru(ttpyA) 2] 0, there are no long-range electrostatic repulsions with the electron acceptor methyl viologen (MV 2+), and the surface COO − groups are suitably disposed for a close-range, 1:1 supramolecular pre-association with MV 2+.