Luminescence quenching of mixed-ligand ruthenium (II) complexes by different quenchers

The effect of ionic strength and acidity (pH) on the luminescence quenching of the excited states of a number of mixed-ligand Ru(II) complexes have been studied. The mixed-ligand Ru(II) complexes of diphenyl-thioethylene (dpte); 2,2-bipyridine (bpy), 2-(2-pyridyl)-quinoline (pyq); 4,6-dichloro-2-(2-pyridyl)pyrimidine (dcppm); 4,6-dichloro-5-methyl-2-(2-pyridyl)pyrimidine (dcmppm); 4,6-dichloro-5-phenyl-2-(2 pyridyl)pyrimidine (dcpppm) with three quenchers: N,N,N',N'-tetramethyl-p-phenlyenediamine (TMPD2+), methyl viologen (Mv(2+)), and ethylenediaminetetraacetic acid (EDTA) have been used to study the effect of acidity. Whereas, for the effect of ionic strength, [Ru(dpte)(2)(dcpppm)](2+) /EDTA system has been used. The quenching rate constant (k(q)) was found to increase with decreasing the ionic strength, while pH has the opposite effect. The quenching of mixed-ligand Ru(II) complexes by TMPD2+ in aqueous solutions was shown to be dynamic and static in nature.