Quantum Mechanical Approach to Kinetic Modeling of Singlet Oxygen Generation: A Case Study of Heavy-Atom-Free Photosensitizers

Singlet oxygen (¹O₂) generation involves an intermolecular energy transfer (EnT) process between a photosensitizer and molecular oxygen. In particular, evaluating the kinetics that govern singlet oxygen production remains a significant challenge. In this work, we employ a simple computational protocol for kinetic calculations to estimate the EnT process. Here, we adapt the classical Marcus theory to determine the free energy barrier of the process and provide a qualitative performance analysis of the model in comparison to the experimental data for a series of organic chromophores. We also perform excited state analyses to understand the higher excited states and their relationship. This work offers a simple computational framework for straightforward calculations of the kinetics of singlet oxygen generation in molecular photosensitization.