The ground state of AB is a closed-shell singlet. The excited states of AB are derived by promotion of an electron from the nitrogen (azo) bridge (relevant MOs are π and lone-pair n; see Fig. ). The first excited singlet state is a dark nπ * transition. The second excited singlet state is a bright ππ * transition. At the EOM-EE-CCSD/aug-cc-pVDZ level of theory, the energies of these transitions are 3.055 eV and 4.465 eV, respectively. In both states, electrons of the nitrogen bridge MOs are promoted to an antibonding orbital, effectively weakening the double bond and lowering the barrier along the cis-trans rotation coordinate. Below, we refer to the excited states generated by transitions localized on the AB scaffold as the AB-like states, or the scaffold-like states.