Determination of the T1 state energy levels of metalloporphyrins using temperature-dependent time resolved spectroscopy
The determination of the energy of the lowest triplet excited state (ET1) for metalloporphyrin photosensitizers, a key parameter for rationalizing energy transfer processes in metalloporphyrins, facilitates a better understanding and optimization of their functionality. In this study, a strategy was proposed for determining the ET1 values in metalloporphyrin systems by analyzing the temperature dependence of the oxygen quenching rate constant using time-resolved spectroscopy, with Platinum(II) octaethylporphyrin (PtOEP) and Palladium(II) octaethylporphyrin (PdOEP) as representative examples. Through a thermal equilibrium approximation of the excited triplet state (T1) and the excited state of oxygen, a theoretical model was introduced in which the oxygen quenching rate exhibits a nonlinear dependence on temperature, enabling the determination of ET1 values. Additionally, the validity of this approach was demonstrated through excitation spectra of metalloporphyrins. Our work provides an effective pathway and offers new insights into the energy-loss mechanisms involved in related photoconversion processes.
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