Phosphonate-functionalized heteroleptic ruthenium(II) bis(2,2':6',2''-terpyridine) complexes

The heteroleptic complexes [Ru(1)(4)][PF6](2), [Ru(2)(4)][PF6](2), [Ru(Phtpy)(4)][PF6](2), and [Ru(pytpy)(4)][PF6](2) (Phtpy = 4'-phenyl-2,2':6',2 ''-terpyridine, pytpy = 4'-(4-pyridyl)-2,2':6',2 ''-terpyridine, 1 and 2 = 4-methyl ester substituted derivatives of Phtpy and pytpy, 4 = ethyl 2,2': 6',2 ''-terpyridine-4'-phosphonate) have been prepared. The single crystal structure of ligand 1 (1 = methyl 4-carboxy-4'-phenyl-2,2':6',2 ''-terpyridine) is reported. The introduction of the 4-methyl ester group causes a small red shift in the MLCT band of the ruthenium(II) complexes and a small shift to a more positive potential for the Ru2+/Ru3+ couple. The new complexes should serve as a useful starting point for development of ruthenium(II) dyes suited for sensitization of p-type semiconductors.