Charge Transfer Is Promoted by Electronic Heat Exchange in Atoms and Molecules.

This work compiles almost a decade of theoretical progress in temperature-dependent chemical reactivity theory to introduce the first finite-temperature charge transfer model, predicting fractional electron transfers during chemical interactions. The key insight is that electronic heat drives charge transfer. By analyzing thermodynamic parameters like electronic heat capacity, softness, and chemical potential, the framework explains how species transition from inert to reactive states, where electrons are decorrelated enough to enable charge transfer. A crucial aspect of this model is the role of thermal fluctuations, which governs molecular response functions and facilitates the simultaneous exchange of energy and charge. This model is reduced to a simple linear equation in the chemical potential of the reservoir. When extrapolated, it supports the electrophilicity index, adding a correction term and providing a working formula more influenced by electron affinity. These findings offer new pathways to analyze and predict chemical interactions under the finite temperature regime.