Large electro-optic activity and enhanced thermal stability from diarylaminophenyl-containing high-β nonlinear optical chromophores

Two series of highly efficient and thermally stable nonlinear optical chromophores based on the (4-diarylamino)phenyl electron donors have been synthesized and systematically investigated. A modular approach has been employed to synthesize these electron donors with tunable size, shape, and electrondonating abilities. Efficient conjugated bridges were extended from these donors and coupled with very strong CF₃-TCFelectron acceptors to afford chromophores with very high β alues (up to 7077 × 10 ^-30 esu at 1.907 μm). These chromophores possess much higher thermal stability (with their onset decomposition temperatures all above 220°C) than those substituted with (4-dialkylamino)phenyl donors. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into very large electro-optic (E-O) coefficients (r ₃₃) in poled polymers through suitable shape engineering. Exemplified by the chromophore B4, which has a fluorinated aromatic substituent anchored at its donor end, it showed a very large r₃₃ (169 pm/V) at 1.31 μm. This value is almost 1 order higher than the E-O activities usually reported for (4-diarylamino)phenyl-substituted NLO chromophores.