Design and synthesis of various double donors for nonlinear optical chromophores with enhanced electro-optic activity

Eight nonlinear optical chromophores L1-2, M1-2, N1-2 and O1-2 based on the diethylaniline bis(N,N-diethyl)aniline, bis(N-Ethyl-N-hydroxyethyl)aniline and bis(3-hydroxypiperidin)aniline donor and thiolated isophorone bridge were designed and synthesized. In particular, the bridge sections of the molecules were functionalized with tert-butyltrimethylsilane and tert-butyl(methyl)diphenylsilane isolation groups, respectively. All these eight chromophores exhibited high thermal stabilities with decomposition temperatures above 220 °C. Density functional theory calculations indicated that the chromophores M1-2, N1-2 and O1-2 showed much larger hyperpolarizability than chromophores L1-2 with single donor due to the double donors structure. A large r33 value (198 p.m./V) and poling efficiency (2.03 ± 0.09 nm2/V2) at 1310 nm have been achieved for polymer films containing chromophores N2 which was much larger than the value (104 p.m./V and 1.03 ± 0.05 nm2/V2) of chromophore L2 with single donor. The reasonable design of these double donors can effectively improve the electron donating ability of donors and be applied to advanced organic nonlinear materials.