Site-isolated electro-optic chromophores based on substituted 2,2'-Bis(3,4-propylenedioxythiophene) π-conjugated bridges

Application of bis(propylenedioxythiophene) (bis(ProDOT)) π-conjugated bridges bearing alkyl or aryl substituents in electro-optic (EO) chromophores is presented. A series of three bis(ProDOT)-based chromophores and a bithiophene-based control chromophore were prepared and fully characterized with regard to EO applications. The highly planar bis(ProDOT) bridge results in slightly larger (̃10%) molecular hyperpolarizability (β) values as compared to the bithiophene bridge, as measured by hyper-Rayleigh scattering at a variety of wavelengths. In amorphous polycarbonate guestfilms, however, the bulky substituents on the bis(ProDOT) bridge result in significantly larger (̃70%) poling-induced EO coefficient (r₃₃) values, as measured by simple reflection ellipsometry at 1310 nm. This can be attributed to a roughly 2enhancement in poling efficiency due to reduced intermolecular dipole-dipole interactions. This chromophore architecture also exhibits excellent temporal alignment stability and photochemical stability as compared to benchmark AJL8, FTC, and CLD chromophore systems. Incorporation of the strong CF₃-phenyl-substituted tricyano-furan (TCF) acceptor into a bis(ProDOT)-based chromophore resulted in a β_zzz(- 2ω;ω,ω) value at 1907 nm of 5700 ± 400× 10 ³⁰ esu and an r³³ value of 69 ± 14 pm/V at 32.8 total chromophore weight %. © 2008 American Chemical Society.