Ground State Orbital Analysis Predicts S1 Charge Transfer in Donor–Acceptor Materials

Donor-acceptor (D-A) materials, such as D-A co-crystals and D-A copolymers, can exhibit a wide range of unique photophysical properties with applications in next-generation optoelectronics. Identifying structure-function relationships to predict properties of materials from molecular features is a key challenge in the development of rational design principles. In this communication we present a novel metric for predicting the degree of charge transfer (DCT) in the S1 electronic state of D-A materials, using ground state orbital analysis. This metric computes the average of two quantities: (1) the degree of similarity between the highest occupied molecular orbital (HOMO) in the donor molecule and the D-A complex and (2) the degree of similarity between the lowest occupied molecular orbital (LUMO) in the acceptor molecule and the D-A complex. We demonstrate a linear relationship between this similarity metric and the DCT in the S1 state (HOMO → LUMO transition) for a data set of 31 D-A dimers. We discuss the integration of this novel orbital structure-function relationship into high-throughput screening methods and suggest best practices for choosing both molecular geometries and methods for computing the DCT.