Preparation and photophysical properties of precursors of inorganic macromolecules. Mono and binuclear complexes of Ru(II) and terpyridine derivatized with thiophene and 4′-(5-bromothiophene) groups

The preparation and characterization of mono and binuclear complexes of Ru(II) with a newly synthesized derivate of the terpyridine ligand, 4′-(5-bromothiophene)-2,2′,6′,2″-terpyridine, are communicated. In the binuclear complex, 2,5-bis(2,2′,6′,2″-terpyridine-4′yl)thiophene was used as a bridge between two Ru(II) centers. The new compounds were characterized by H NMR, UV–Vis and IR spectroscopies. Bands at ∼500 nm for the Ru(II) to terpyridine charge transfer transition and absorption bands at λ<400 nm assigned to intraligand transitions, π*←π, centered in the tpy moiety were observed in the UV–Vis spectra of the complexes. Irradiation of the complexes in CH3CN at 337 or 500 nm induced luminescence with maxima at ∼670 nm and lifetimes τ⩽102 ns. Time-resolved absorption spectroscopy revealed the formation of long-lived species during the decay of the metal to ligand charge transfer excited states. The intermediates were tentatively assigned as unstable products of ligand-substitution or orthometalation excited state reactions.