Switching to ESP embedding, we see-just like in G 4 -a large improvement in the results for MgG . ECIS+ESP produces RMSDs for the energies of 0.28 eV for singlets and 0.14 eV for triplets (overestimating the excitation energies much less than FDA). While the triplet states show the expected degeneracy pattern (compared to the reference), for the S 5 -S 8 states ECIS+ESP predicts a 2:1:1 pattern instead of a 1:2:1 pattern, and the splitting of these states is notably too small. Similarly, the order of the bright and dark states differs between the reference and ECIS+ESP. This is most likely caused by the residual GS-LE couplings, which affect only the energy of the totally symmetric linear combination of the LE excitations (and the ground state). Hence, whereas the totally symmetric excitation is S 5 for the reference, it becomes S 8 for ECIS+ESP (see Table ). Nevertheless, we note that the GS-LE couplings are dramatically reduced in ECIS+ESP compared to ECIS+FDA. The ECIS+ESP full-system ground state only exhibits an admixture of 1% of LE products (compared to 5% for ECIS+FDA), and the S 8 state contains only 0.3% admixture of the GS product. The reduction of GS-LE couplings is expected to improve size extensivity for ECI+ESP compared to ECI+FDA. Similarly, excitonic correlation in ECIS+ESP is strongly reduced, best visible in the PR values in Table . This disappearance of excitonic correlation when applying ESP embedding is analogous to the disappearance of multireference character of electronic states when appropriate rotation of molecular orbitals is applied. Nevertheless, the site states obtained by ESP embedding are still not adequate to form a sufficiently accurate basis for ECIS.