Synthesis, characterization and evaluation of nonlinear optical properties of chiral hydrobenzoin monomers

Four new monomers have been synthesized by condensation of the chiral pure reagents (R,R)-(+)-1,2-diphenyl-1,2-ethanediol and (SS)-(-)-1,2-diphenyl-1,2-ethanediol ((R,R)-(+)-hydrobenzoin and (SS)-(-)-hydrobenzoin, respectively) with methacryloyl chloride with the purpose of preparing structures that exhibit second harmonic generation of laser light and to polymerize them by free radical polymerization. The monomers (R,R)-(+)-1,2-diphenyl(2-methacryloyloxy)ethanol, (S,S)-(-)-1,2-diphenyl(2-methacryloyloxy)ethanol, (R,R)-(+)-1,2-diphenyl(1,2-dimethacryloyloxy)-ethane and (SS)-(-)-1,2-diphenyl(1,2-dimethacryloyloxy)-ethane were obtained and characterized by melting point measurements, infrared spectroscopy, nuclear magnetic resonance spectroscopy, gas chromatography with mass spectroscopy and polarimetry. The optical properties evaluation was made following the Kurtz and Perry modified procedure in powder form and using a Nd:YAG laser as pulse light source (approximate to0.466 mJ/mm(2)) at 1064 urn. The second harmonic generated light (532 nm) from each compound was compared with the calibration spectrum of a chiral compound (saccharose or sucrose, know as sugar) used as a standard. The second harmonic generation values measured showed that R,R(+)-1,2-diphenyl(2-methacryloyloxy)ethanol and (SS)-(-)-1,2-diphenyl(2-methacryloyloxy)ethanol enantiomers had better efficiency of second harmonic generation than (R,R)-(+)-1,2-diphenyl(l,2-dimethacryloyloxy)ethane and (SS)-(-)-1,2-diphenyl(1,2-dimethacryloyloxy)ethane under the same conditions. In other words, the monoacylation products worked much better than the diacylation products or the hydrobenzoin enantiomers themselves from the SHG behavior point of view. Keywords: (R,R)-(+)-Hydrobenzoin; (SS)-(-)-hydrobenzoin; (R,R)-(+)-1,2-diphenyl(2-methacryloyloxy)ethanol; (SS)-(-)-1,2-diphenyl(2-methacryloyloxy)-ethanol; (R,R)-(+)-1,2-diphenyl(l,2-dimethacryloyloxy)ethane; (SS)-(-)-1,2-diphenyl(1,2-dimethacryloyloxy)ethane; chiral monomers; second harmonic generation; nonlinear optical properties.