Calculation of the susceptibility of aromatic compounds with a localized MO model

Using previously derived equations for the susceptibility [8] we calculated the components of the susceptibility tensor for ethene, benzene and naphthalene. Starting from PCILO bond orbitals and energy localized orbitals we evaluated theoretical increments for the susceptibility of the bonds building up these molecules. It was demonstrated that only with banana bonds was it possible to obtain satisfactory mean values and the right sign of the anisotropy, whereas a bond scheme with ∝ and π bonds yielded considerably worse values. The benzene value of X m =−712·6×10 −12 m 3 mol −1 resulted from a Kekulé structure with three a bonds and three pairs of r bonds and the naphthalene value of X m =−1137·4×10 −12 m 3 mol −1 from a similar bond scheme.