Preparation and photoluminescence characteristics of polysiloxane pendant tris(2,2′‐bipyridine)ruthenium (II) complex

Polysiloxanes containing pendant tris(2,2′-bipyridine)ruthenium(II) complex (Ru(bpy)32+) were prepared by reaction of polysiloxane-pendant 2,2′-bipyridine (PSiO-bpy) with cis-Ru(bpy)2Cl2. In methanol solution, the polymer pendant Ru(bpy)32+ showed absorption maximum at 456nm and emission maximum at around 609nm, both of which are shifted to longer wavelength than the monomeric Ru(bpy)32+. The lifetime τ0 of the excited polymer complex with low Ru(bpy)32+ content was almost the same as that of the monomeric one in methanol (830ns), but τ0 of the polymer with higher complex content was shorter because of a concentration quenching. In a solid state, τ0 was much shorter (306–503ns) than that in a methanol solution contrary to the conventional polymeric system. Higher complex content in the polymer film caused higher glass transition temperature (Tg), but shorter τ0. These results indicate concentration quenching in the polymer film. The excited polymer pendant Ru(bpy)32+ was quenched by oxygen, and the relative emission intensity followed the Stern-Volmer equation. In a methanol solution the quenching rate constant (kq) was the same order of magnitude as the monomeric complex, and independent of the complex content in the polymer. In a film, kq was higher for the polymer with higher complex content.