A tricyanopyrroline-based nonlinear optical chromophore bearing a lateral moiety: A novel steric technique for enhancing the electro-optic effect

Tricyanopyrroline-based nonlinear optical chromophores bearing a thienyl or phenyl group perpendicular to the long molecular axis, so as to separate the conjugation planes of the parent chromophore, were synthesized. The incorporation of such a lateral group into the molecular backbone of the colorant, together with the use of a strong tricyano-based acceptor moiety influenced nonlinear optical character. The compounds displayed significantly improved electro-optical properties within a polymer host after poling; values of the electric-optic coefficient of amorphous polycarbonate samples imbibed with the chromophores bearing a phenyl and a thienyl moiety were 32 and 40 pm/V, respectively, which were significantly greater than those of the polymer host bearing the chromophore which did not contain a lateral moiety (∼19 pm/V). The attachment of a lateral group to the chromophore increases electro-optic character after poling by suppressing electrostatic interactions.