Kinetic study on bimolecular photochemical quenching of tris(2,2′-bipyridyl)ruthenium(II) complex in water–ethylene glycol binary media

The bimolecular photochemical quenching of the tris(2,2′-bipyridyl)ruthenium (II) complex by ferricyanide ions in water–ethylene glycol binary media was investigated using a spectrophotometric approach, as previously reported by our research group. Time-resolved spectroscopy revealed that dynamic photochemical quenching occurred via a diffusion-dominated pathway. The static quenching process was found to occur significantly when the concentration of ethylene glycol was greater than 40 wt%. The analysis of the Stern–Volmer plots revealed that the emitters and quenchers tended to show ionic associations in water–ethylene glycol compared to our previous results with a water–glycerol binary solvent system. This is attributed to hydrophobicity, which is consistent with pioneering works that report that the addition of ethylene glycol to pure water forms hydrophobic regions, leading to dehydration of the complex ions.