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

Abstract

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 μm by the electric-field-induced second harmonic (EFISH) technique through the β×μ 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 π-backbone, βμ = 1560 × 10⁻³⁰ D cm⁵ esu⁻¹, showing a three-fold increase with respect to the ligand 1c (βμ = 542 × 10⁻³⁰ D cm⁵ esu⁻¹). Third-order nonlinearities, in solid films, were evaluated employing the third harmonic generation (THG) Maker Fringe technique showing χ⁽³⁾ susceptibilities of the order of χ⁽³⁾∼10⁻¹² esu at the infrared wavelength of 1.2 μm. Compounds with the highest χ⁽³⁾ values correspond to those having the largest βμ product: for 1cχ⁽³⁾ = 1.1 × 10⁻¹¹ esu and for 2cχ⁽³⁾ = 8.4 × 10⁻¹² esu.