Although there is no NBO between V and O3 for 24, there is electron density between V and O3 from delocalization as found in the second order perturbative mixing. Namely there is mixing between the lone pair of O3 with the antibonding orbital between V-O1 and with an extremely large E2 stabilization energy of 171 kcal/mol (Table ). Furthermore, the NBO results for 25 reveal a large amount of perturbative mixing (i.e., delocalization) between the equatorial V-O bonding orbitals with the adjacent equatorial V-O antibonding orbitals which is not present in the triprotonated 24. Table lists for 24 the two V-O bond orbitals which mix with the adjacent antibonding V-O bond orbitals. In the case of quadprotonated 25, Table lists sixteen equatorial V-O bond orbitals which are mixing with adjacent V-O antibonding orbitals. This mixing in 25 is exemplified in Figure in which the overlap is illustrated for the case of V-O1 bond orbital as the donor and V-O2 antibonding orbital as the acceptor. It is also interesting that although there is no NBO between axial O4 and V, there is significant delocalization shown in the perturbative mixing. Figure shows this mixing between the donor orbital (i.e., the lone pair on O4) and the acceptor orbital (i.e., the antibonding orbital V-N5) which has significant density in the area of V-O4 bond with stabilization energy (E2) of 60.70 kcal/mol.