Water-soluble pH probes based on P(V) porphyrins

The pH of the medium is a critical parameter for many cellular processes, making pH-monitoring essential for numerous biological and medical applications. This study investigates the pH-sensing properties of water-soluble phosphorus(V) porphyrins. It has been demonstrated that P(V) porphyrins, bearing both axial -OH ligands and N-containing meso-pyridyl substituents, possess several different fluorescent acid-base forms when the pH of the medium changes. Thus, the P(V) mono-pyridyl-three-phenyl porphyrin with an axial OH-group demonstrates four different fluorescence forms, depending on the pH. Therefore, these complexes can serve as potential fluorescent pH sensors in aqueous media in the wide pH range (2.0–12.5).