3 COORDINATE PHOSPHORUS AND BORON AS PI-DONOR AND PI-ACCEPTOR MOIETIES RESPECTIVELY, IN CONJUGATED ORGANIC-MOLECULES FOR NONLINEAR OPTICS - CRYSTAL AND MOLECULAR-STRUCTURES OF E-PH-CH=CH-B(MES)2, E-4-MEO-C6H4-CH=CH-B(MES)2, AND E-PH2P-CH=CH-B(MES)2 [MES = 2,4,6-ME3C6H2]

Hydroboration of π-donor substituted alkynes D-C≡C-H [D = Ph 2P, 4-X-C6H4- (X = H, MeS, MeO, H 2N), and (η5-C5H5) Fe(η5-C5H4-)] with dimesitylborane {[(mes)2BH]2, mes = 2,4,6-Me3C 6H2} yields air-stable 'push-pull' E-alkenes of the form E-D-CH=CH-B(mes)2, which possess large molecular hyperpolarizabilities, β, as shown by electric-field induced second-harmonic generation (EFISH) experiments at 1.91 μm; single crystal X-ray diffraction studies indicate that E-Ph-CH=CH-B(mes)2 and E-4-MeO-C6H4-CH=CH-B(mes)2 crystallise in centrosymmetric space groups, whereas E-Ph2P-CH=CH-B(mes)2 crystallises in the acentric space group P21212 1 and exhibits powder SHG of 1.064 μm laser light.