Synthesis and non-linear optical characterization of novel borinate derivatives of cinnamaldehyde

Herein is reported the synthesis of three new borinates (2a-2c) derived from bidentate imine ligands (1a-1c), which were prepared from the corresponding cinnamaldehyde derivatives. All compounds were characterized by MS, IR and NMR spectroscopy. The nonlinear optical (NLO) characterization of these molecules having push-pull properties is included. Second order nonlinearities were evaluated at 1.907 mu m by the electric-field-induced second harmonic (EFISH) technique through the beta x mu product, showing a trend for a general increase of the NLO response after boron complexation. For borinate 2c, which has strong electron-donating and electron-withdrawing groups at opposite ends of the pi-backbone, beta mu = 1560 x 10(-30) D cm(5) esu(-1), showing a three-fold increase with respect to the ligand 1c (beta mu - 542 x 10(-30) D cm(5) esu(-1)). Third-order nonlinearities, in solid films, were evaluated employing the third harmonic generation (THG) Maker Fringe technique showing chi((3)) susceptibilities of the order of chi((3)) similar to 10(-12) esu at the infrared wavelength of 1.2 mu m. Compounds with the highest chi((3)) values correspond to those having the largest beta mu product: for 1c chi((3)) = 1.1 x 10(-11) esu and for 2c chi((3)) = 8.4 x 10(-12) esu.