Our calculations use the molecular exciton basis, with Hartree-Fock (HF) MOs localized on individual monomers. Depending on the compound, we have retained between 24 to 30 exciton basis MOs, of which 4-6 are localized on the bridge molecules, with equal numbers of bonding and antibonding MOs (see SI). Further details may be found in previous studies and in the SI. To arrive at the precise description of the two electron-two hole (2e-2h) (𝑇𝑇) ( excitation, we use the multiple reference singles and doubles configuration interaction (MRSDCI) approach, which includes configuration interactions with the most dominant 4e-4h excitations. The total number of many-electron configurations retained to describe any single eigenstate is several million. In addition to the wavefunctions and energies, we also calculate the transition dipole couplings from the ground state to all excited states and the linear absorption spectra.