Synthesis, photophysical, electrochemical, and ion-binding properties of Ru(II) polypyridyl complexes containing benzo-15-crown-5

摘要

Two polypyridyl ligands, 5-(4′-ethynylbenzo-15-crown-5)-2,2′-bipyridine (L1) and 3-bromo-8-(4′-ethynylbenzo-15-crown-5)-1,10-phenanthroline (L2), and their Ru(II) complexes [(bpy)2RuL](PF6)2 have been prepared and characterized. Both complexes exhibit metal-to-ligand charge transfer absorption at around 452 nm and emission at around 640 nm in MeCN solution. Electrochemical studies of the complexes reveal a Ru(II)-centered oxidation at around 1.31 V and three ligand-centered reductions. The binding ability of the complexes with Na+ has been investigated by UV/Vis absorption, emission, and electrochemical titrations. Addition of Na+ to MeCN solutions of both complexes results in a progressive enhancement of the emission, a red-shift of the UV/Vis absorption, and a progressive cathodic shift of the Ru(II)-centered E 1/2 couple. The stability constants for the 1:1 stoichiometry adducts of the complexes with Na+ have been obtained from the UV/Vis absorption titrations.