Singlet¡Vsinglet and singlet¡Vtriplet annihilations in structure-regulated porphyrin polymers
Journal
Journal of Photochemistry and Photobiology A: Chemistry
Journal Volume
331
Pages
56-59
Date Issued
2016
Author(s)
Abstract
In the present paper, we investigated migration processes of the S1 and T1 states in polycyclobutene bearing zinc porphyrin as a pendant group. Transient absorption spectra during femtosecond laser flash photolysis showed a fast decaying component, which can be attributed to singlet–singlet (S–S) annihilation resulted from migration of the S1 state among the porphyrin units. Decay kinetics of the S1 state were well characterized by the time-dependent annihilation model, indicating interaction between the excited states. In addition, polymers with high Z/E ratio showed fast annihilation, demonstrating importance of the ordered structure. On the other hand, in low temperature glassy matrix, fluorescence decay profiles of all polymers showed a enhanced fast decaying component, when laser fluence and/or repetition became higher, indicating the quenching of the S1 state by accumulated T1 state (S–T annihilation). Similar annihilation rates were found with three kinds of polymers, indicating the structural change due to low temperature. The present study demonstrated importance of the stacked structure both in the S1 and T1 migration processes.
SDGs
Type
journal article