Incorporation of a Stilbazole Derivative in the Hydrogen-Bonded Chain of l -Tartrate: Toward a One-Step Optimization of Molecular and Bulk Second-Order Nonlinearities

The syntheses and crystal structures of dimethylaminostilbazole (DAS) and dimethylamino- N -methyl stilbazolium hydrogen l -tartrate (DAS-H + Ta - ) are described. Crystal data for DAS: monoclinic, P 2 1 / c, a = 6.0443(9) Å, b = 7.6616(8) Å, c = 26.376(4) Å, β = 93.66(1)°, Z = 4. Crystal data for DAS-H + Ta -: monoclinic, P 2 1, a = 7.518(1) Å, b = 7.528(1) Å, c = 16.376(2) Å, β = 92.67(1)°, Z = 2. In the latter compound, the anions create infinite chains through intermolecular O−H···O hydrogen bonds, whereas the stilbazolium cations are hydrogen bonded to the chains. INDO calculations and spectroscopic studies show that hydrogen bonding greatly enhances the molecular hyperpolarizability of the stilbazole derivative, while crystal engineering with tartaric acid is achieved into the acentric space group. Therefore, an efficiency of 8 times that of urea in second-harmonic generation has been measured at 1.907 μm for this material.