The Role of Theoretical Calculations for INVEST Systems: Complementarity Between Theory and Experiments and Rationalization of the Results

Abstract Here, the key role played by theoretical calculations for molecules presenting an inverted singlet‐triplet excited state (e.g. S 1 and T 1 ) energy difference, or Δ E ST < 0, whose interest has steadily raised in recent years fostered by experimental advances showing negative Δ E ST values for a collection of real‐world systems is reviewed. The evolution of the computational efforts from the pioneering calculations on a reduced set of prototypical systems is covered, to high‐throughput virtual screenings of thousands of molecules to identify new molecular scaffolds or tune properties other than the excitation energies, and describe the necessary benchmarking of the methods done in parallel along the years. Overall, the complementarity of theoretical and experimental advances has prompted the discovery of more and more systems displaying Δ E ST < 0 values, whose basic design principles are rationalized and are thus reviewed here too, while allowing at the same time to find which methods offer a reasonable trade‐off between accuracy and computational cost.