Computational modeling of triplet energy transfer processes: progress and future challenges

In this feature article, we review progress and future challenges in the development of computational approaches for modelling triplet energy transfer processes. These processes are of fundamental importance for understanding biological systems, developing new synthetic chemistry tools, photochemistry and transition-metal based photocatalysis, as well as designing materials with improved properties. Describing these processes requires calculation of diabatic states where the character of the wavefunction is constant across the reaction coordinate. Diabatic states are often difficult to access directly and are poorly defined when trying to construct them from more easily obtained adiabatic states. Another challenge is determining how to properly include the charge transfer states in the theoretical framework. Here, we review the previous developments within the field, as well as our recent work on triplet energy transfer. Subsequently, we highlight the future directions and challenges that remain to provide reliable and computationally expedient predictions of triplet energy transfer kinetics.