title: Three-dimensional nonlinear optical chromophores based on through-space delocalization.
abstract: Six permutations of 4-fold donor and/or acceptor substitution of paracyclophane at the 4, 7, 12, and 15 positions were synthesized to probe the phenomenon of three-dimensional delocalization on the nonlinear optical properties of organic materials. The interplay between through-bond intramolecular charge transfer (ICT) as well as three-dimensional, or through-space, ICT processes gives rise to large quadratic hyperpolarizability values. The determination of dipolar (beta(J)(=1)) and octupolar (beta(J)(=3)) irreducible tensor contributions to the overall beta tensor value is made possible by the polarized harmonic light scattering technique at 1.32 microm. The electric field-induced second-harmonic generation technique was also used at 1.91 microm for comparison. Significant experimental beta values for members of the series made of two centrosymmetric benzene-like units are a clear signature of a purely through-space ICT between two aryl subunits. The two configurational isomers that pair two dipolar donor-acceptor chromophores also exhibit octupolar character. Analysis of these two with an additive model for beta(J)(=1) and beta(J)(=3) reveals a strong three-dimensional inter-ring charge transfer.
authors.affiliation: Department of Chemistry, Institute for Polymers and Organic Solids, University of California, Santa Barbara 93106, USA.
authors.forename: Glenn P
authors.initials: GP
authors.lastname: Bartholomew
authors.forename: Isabelle
authors.initials: I
authors.lastname: Ledoux
authors.forename: Shaul
authors.initials: S
authors.lastname: Mukamel
authors.forename: Guillermo C
authors.initials: GC
authors.lastname: Bazan
authors.forename: Joseph
authors.initials: J
authors.lastname: Zyss