화학공학소재연구정보센터
Inorganic Chemistry, Vol.47, No.14, 6532-6540, 2008
Ruthenium tris(bipyridine) complexes with sulfur substituents: Model studies for PEG coupling
Ruthenium polypyridyl complexes are incorporated into polymers for sensing and light emitting materials applications. Coupling reactions between metal complexes and polymers are one route to polymeric metal complexes. In an effort to increase conjugation efficiency, tune materials properties, and introduce a responsive crosslink, ruthenium tris(bipyridine) derivatives with sulfur substituents were synthesized and compared to oxygen analogues. Difunctional thiols, thioesters, thioethers, and disulfides, as well as hexafunctional nonpolymeric model systems, were explored. Upon exposure to oxygen, the thiol derivative was readily oxidized. These studies guided Ru(bpy)(3) PEG coupling reactions with disulfide and thioether linkages, which proceeded to similar to 80% and similar to 60% yield, respectively. The luminescence properties of the Ru PEG derivatives and model systems were investigated. The emission spectra and lifetimes for all complexes in CH3CN under an inert atmosphere are comparable to [Ru(bpy)(3)]Cl-2. Lifetime data for nonpolymeric analogues fit to a single exponential decay indicating heterogeneity, suggesting sample homogeneity, whereas data for polymers fit to a multiexponential decay. In contrast to certain [Ru(bpy)(3)](2+)/thiol mixtures, no intramolecular quenching by the sulfide is observed for [Ru(bpy)(2){bpy(CH2SH)(2)}](PF6)(2). Emission spectra red shift and multiexponential decay are noted for the oxidized Ru thiol product. The rates of oxygen quenching are slower for Ru PEG derivatives than those for nonpolymeric analogues, which may be attributed to shielding effects of the polymer chain.