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

Abstract

Mono and binuclear complexes of Ru(II) with a newly synthesized derivate of the terpyridine ligands, 4 ′ -(5-bromothiophene)-2,2 ′ ,6 ′ ,2″-terpyridine, (I), and 2,5-bis(2,2 ′ ,6 ′ ,2″-terpyridine-4 ′ yl)thiophene, (II), have been prepared and characterized via UV–Vis, NMR and IR spectroscopies. Photophysical and photochemical processes of the complexes were also investigated. 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 CH 3 CN at 337 or 500 nm induced luminescence with maxima at ∼670 nm and lifetimes τ ⩽10 2 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.