Triplet Distribution in a Symmetrical Zinc(II) Porphyrin–BODIPY Pentameric Array

Abstract

A symmetrical molecular array has been synthesized comprising a central zinc(II) 5,10,15,20-tetraphenylporphyrin with identical boron dipyrromethene (BODIPY) units appended at each of the meso sites. Excitation of any subunit causes a cascade of electronic energy-transfer steps, ultimately leading to the BODIPY triplet-excited state in high yield. Coincidentally, the triplet energy levels of the zinc(II) porphyrin and BODIPY appendage are closely balanced such that an equilibrium is established at both 77 K and room temperature. This fast equilibration allows global distribution of the triplet exciton around the array, leading to a significantly increased capture volume for bimolecular quenching and a substantial increase in the rate constant for bimolecular triplet−triplet annihilation. The corresponding free-base porphyrin analogue does not favor triplet exciton decentralization because of the large disparity in the electronic energy levels.

Caging of Bodipy Photosensitizers through Hydrazone Bond Formation and their Activation Dynamics

“…Based on the differences of these variables between the healthy and malignant tissues it is possible to design a PS to function in the part of interest selectively. Among the PSs, Bodipy compounds are proved to be one of the principal candidates and they are still employed in novel strategies and for better understanding the structure‐function relationships [15] …”

“…Among the PSs, Bodipy compounds are proved to be one of the principal candidates and they are still employed in novel strategies and for better understanding the structure-function relationships. [15] Among the activation pathways of the PSs, we are mainly interested in pH activation, as cancerous cells and/or tumor microenvironment were known to be acidic compared to the healthy cells. Some literature reports describe the intracellular pH of cancer cells as acidic, [16,17] however, some of them report the extracellular matrix of tumor regions as acidic.…”