Synthesis and optical nonlinear property of Y-type chromophores based on double-donor structures with excellent electro-optic activity

New Y-type chromophores FTC-yh1 and FTC-yh2 containing bis(N, N-diethyl) aniline as a novel electron-donor, thiophene as a p-conjugated bridge and tricyanofuran (TCF) as an acceptor have been synthesized and systematically investigated in this paper. Density functional theory (DFT) was used to calculate the HOMO-LUMO energy gaps and first-order hyperpolarizability (beta) of these chromophores. These chromophores showed better thermal stability with their decomposition temperatures all above 240 degrees C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r(33)) in poled polymers. The doped film-A containing 25 wt% chromophore FTC-yh1 displayed a value of 149 pm V-1 at 1310 nm, and the doped film-B containing FTC-yh2 showed a value of 143 pm V-1 at the concentration of 25 wt%. These values are almost four times higher than the EO activity of usually reported traditional single (N, N-diethyl) aniline nonlinear optical (NLO) chromophores FTC. High r(33) values indicated that the double donors of the bis(N, N-diethyl) aniline unit can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of the new chromophores as advanced material devices.