Elucidating the Reaction Kinetics of Hydrophobic Porphyrin Nanoaggregates Dispersed in PVA Films Exposed to HCl Vapors

Abstract

The behavior of the absorbance profiles of free‐base 5,10,15,20–tetraphenylporphyrin (TPPH2) and zinc 5,10,15,20‐tetraphenylporphyrinate (ZnTPP) under exposure to HCl vapors was investigated to establish in detail the mechanism of protonation of these porphyrinic compounds and their potential for use as HCl sensors. We show that the intensities of diprotonated tetraphenylporphyrin absorption bands that arise at 444–446 and 662–666 nm increase as a function of the HCl exposure time. Reactions of free‐base meso‐tetraphenylporphyrin protonating and of zinc meso‐tetraphenylporphyrinate demetalation and subsequent protonating are discussed, and the solutions of the corresponding kinetic equations and respective reaction rates are also obtained. Finally, from a theoretical analysis we deduce the presence of intermediated monoprotonated porphyrin that helps us to explain why the isosbestic point in the TPPH2 reaction with HCl is not well defined.

Efficient Energy Transfer (EnT) in Pyrene- and Porphyrin-Based Mixed-Ligand Metal–Organic Frameworks

“…Several control experiments were performed to verify the co-assembly of two ligands in a single MOF. Zinc porphyrin is easily demetalated in hydrochloric acid solution and exhibits a green color due to the protonation of pyrrole moieties in porphyrin. , Obvious color changes from purple to green were observed in the MLMs during the activation step, where an HCl solution was involved. Moreover, individual crystals also became greenish, as shown in the microscopy images (Figures S2 and S3).…”