Phosphorescence and Photophysical Parameters of Porphycene in Cryogenic Matrices

Barbara Golec,Jacek Waluk,Aleksander Gorski

doi:10.3390/photochem2010016

Abstract

Matrix isolation studies were carried out for porphycene, an isomer of porphyrin, embedded in solid nitrogen and xenon. The external heavy atom effect resulted in nearly a 100% population of the triplet state and in the appearance of phosphorescence, with the origin located at 10163 cm−1. This energy is much lower than that corresponding to the T1 position in porphyrin. This difference could be explained by postulating that the orbital origin corresponds in both isomers to the second excited singlet state, which lies much closer to S1 in porphycene. Most of the vibrational frequencies observed in the phosphorescence spectrum correspond to totally symmetric modes, but several ones were assigned to the out-of-plane Bg vibrations. These bands are not observed in fluorescence, which suggests their possible role in vibronic-spin-orbit coupling.

Highlights

IntroductionThe detailed characterization of the photophysical characteristics of a chromophore is a prerequisite for successful applications
Photophysical Parameters ofThe detailed characterization of the photophysical characteristics of a chromophore is a prerequisite for successful applications
Electronic spectroscopy studies of porphycene embedded in xenon matrices enabled an accurate determination of the location of the lowest triplet state

Summary

Introduction

The detailed characterization of the photophysical characteristics of a chromophore is a prerequisite for successful applications. The properties of the triplet state, such as its energy, yield of formation via intersystem crossing from the singlet state, lifetime, and the ability to generate singlet oxygen, are crucial when designing new materials, e.g., photosensitizers, photovoltaic cells, or light emitting diodes. The triplet state parameters often determine the photostability of a molecule, since photodegradation usually involves the triplet state. It is not surprising that large databases containing triplet state data are available for many popular chromophores [1]. One of them is porphyrin, justly called “pigment of life” [2].

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Results

Conclusion