Structure-property correlation in the second hyperpolarizabilities γ for phenyl nitronyl nitroxide radicals

We report a structure-property correlation in the second hyperpolarizabilities γ of phenyl nitronyl nitroxide radicals para-substituted by several donor or acceptor groups. INDO coupled Hartree-Fock calculations and γ density analyses are employed. The variations in the γ by two chemical perturbations, i.e., a rotation of the phenyl ring and an introduction of donor or acceptor substituent groups into the phenyl ring, are investigated in relation to the distribution of the charge density on the nitronyl nitroxide radical unit.