Spectroscopic and photophysical properties of complexes of 4 '-ferrocenyl-2,2 ': 6 ',2 ''-terpyridine and related ligands

4'-(Ferrocenyl)-2,2':6',2 "-terpyridine (Fctpy) and 4'-(4-pyridyl)-2,2':6', 2 "-terpyridine (pytpy) were prepared from the corresponding ferrocene- and pyridinecarboxaldehyle and 2-acetylpyridine using the Krohnke synthetic me thodology. Metal complexes, [M(Fctpy)(2)](PF6)(2) (M = Ru, Fe, Zn), [Ru(tpy )(Fctpy)](PF6)(2) (tpy = 2,2':6',6 "-terpyridine), and [Ru(pytpy)(2)](PF6)( 2) were prepared and characterized. Cyclic voltammetric analysis indicated Ru-III/II and ferrocenium/ferrocene redox couples near expected potentials (Ru-III/II similar to 1.3 V and ferrocenium/ferrocene similar to 0.6 V vs A g/AgCl). In addition to dominant pi(tpy) --> pi(tpy)* UV absorptions near 2 40 and 280 nm and d(pi)(Ru) --> pi(tpy)* MLCT absorptions around 480 nm, th e complexes [Ru(Fctpy)(2)](PF6)(2) and [Ru(tpy)(Fctpy)](PF6)(2) exhibit an unusual absorption band around 530 nm. Resonance Raman measurements indicat e that this band is due to a (1)[(d(pi)(Fc))(6)] --> (1)[(d(pi)(Fc))(5)(pi* (Ru)(tpy))(1)] transition. For [Ru(Fctpy)(2)](PF6)(2) and [Ru(tpy)(Fctpy)]( PF6)(2), excited-state emission and lifetime measurements indicated an uppe r-limit emission quantum yield of 0.003 and an upper-limit emission lifetim e of 0.025 mu s. The influence of the ferrocenyl site on excited-state deca y is discussed, and an excited-state energy level diagram is proposed.