title: Role of spatial distortions on the quadratic nonlinear optical properties of octupolar organic and metallo-organic molecules.
abstract: Following on the recent experimental demonstration of a discrepancy between the nonlinear optical (NLO) behavior of several pi-conjugated chromophores and their assumed octupolar symmetry, the authors investigate how geometrical distortions influence the NLO response of multipolar push-pull molecules. Their analytical model is set on a basis of valence-bond and charge-transfer states to estimate the hyperpolarizability of organic and metallo-organic chromophores using the lowest possible number of variables. Since symmetry breakdown changes the definition of the molecular Cartesian framework, tensorial spherical coordinates are implemented. The evolution of the nonlinear molecular anisotropy with possible rotational deviations is then evaluated for two recently studied chromophores. Zero-frequency calculations show that, outside optical resonance, weak geometrical distortions lead to strong anisotropy variations in agreement with experimental data. Their goal is to underscore which molecular engineering strategies should be applied when designing a photoisomerizable nonlinear octupole.
authors.affiliation: Laboratoire de Photonique Quantique et Moléculaire (CNRS UMR 8537), Institut d'Alembert (IFR 121), Ecole normale Supérieure de Cachan, 61 Avenue du Président Wilson, 94235 Cachan, France. sebastien.bidault@normalesup.org
authors.forename: Sébastien
authors.initials: S
authors.lastname: Bidault
authors.forename: Sophie
authors.initials: S
authors.lastname: Brasselet
authors.forename: Joseph
authors.initials: J
authors.lastname: Zyss
authors.forename: Olivier
authors.initials: O
authors.lastname: Maury
authors.forename: Hubert
authors.initials: H
authors.lastname: Le Bozec