ATC values were computed using the TrESP variant of the ATC method as implemented in Multiwfn, which yields a set of transition charges z that best reproduce the transition potential (rather than partitioning schemes based on population analysis, such as Mulliken charges). This method is described in detail elsewhere. In short, it involves partitioning the space around the molecule into a grid and calculating the transition potential as a function of grid position using the molecular transition density matrix. The molecular transition density matrix was obtained using TD-DFT as described above. Exciton coupling parameters were computed from the ATCs using Equation (1).