Synthesis and pH-Sensing of Simple but Effective Ruthenium(II) Polypyridine Complexes: Potential Lysosome Probes

Abstract

The pH optical sensors work on the principle of pH-related changes in the absorption or emission of a probe. They have generated much interest during the past decades due to their wide applications in fields such as analytical chemistry, biochemistry, clinical medical diagnosis, and environmental monitoring. Two ruthenium(II) polypyridine complexes, [Ru(bpy)₂(hipp)]²⁺ (Ru1) and [Ru(bpy)₂(dcipp)]²⁺ (Ru2), were chosen as pH probes. Here, bpy denotes 2,2-bipyridine, hipp denotes 2-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenol, and dcipp denotes 2,4-dichloro-6-(1H-imidazo[4,5-f] [1,10]phenthrolin-2-yl)phenol, respectively. The pH effects on the absorption and emission spectra of Ru1 and Ru2 were investigated by pH titrations. Ru1 and Ru2 were found to be pH-sensitive and revealed different ionization constants, suggesting their potential use as optical pH sensors and applications in environmental monitoring.