Synthesis and characterization of dendritic nonlinear optical chromophores with double donors

Abstract

Based on the same bis(4-piperidine) phenyl derivative donor, isophorone derivative bridge, and phenyl trifluoromethyl tricyclofuran (3F-TCF) acceptor, two different isolating groups, tert butyldimethylsilyl (TBDMS) and pentafluorophenyl ring (5F-Ph), were introduced into the donor and bridge to synthesize two chromophores XY 1-2. Eight 5F-Ph groups are respectively attached to the donor and bridge segments of the chromophore, which can prevent the molecules from tightly packing and thus improve polarization efficiency. This article systematically investigates the UV absorption, density functional theory (DFT) calculations, thermal stability, and electro-optic activity of these chromophores. The chromophores XY 1-2 exhibit good thermal stability at decomposition temperatures (T_d) greater than 250 °C. Most importantly, rigid steric hindrance groups can effectively reduce dipole–dipole interactions between molecules and improve the conversion efficiency of the first-order hyperpolarization (β) of chromophores into large electro-optic (EO) coefficients (r₃₃). And the poling efficiency of a single XY2 molecule at 1310 nm (0.69 ± 0.01 nm² V⁻²/(10²⁰ molecules per cm³)) is much higher than that of a single XY1 molecule when polarizing the polymer with chromophore XY 1-2.