This stabilization of the 1 πRy 6 state is so strong that it remains in the set of the computed seven singlet states even when ESP embedding is employed, which destabilizes the 1 πRy 6 state strongly due to the negative ESP charges of the neighboring oxygen atom. The other guanine site states in MgG 4 stay qualitatively the same when switching to ESP embedding, only changing their excitation energies to some extent.