| Abstract
| - The principles of crystal engineering have been used to design afamily of structures with potentialas octupolar nonlinear optical (NLO) materials. The major aim insuch an exercise, a carry-over of molecularsymmetry into the crystal, is possible with a retrosynthetic approach.An appropriate choice of precursortrigonal molecules leads from the concept of the dimeric Piedfort unit.The crystal structures and NLO propertiesof a series of 2,4,6-triaryloxy-1,3,5-triazines,1−6, are reported. These compoundsconsistently form quasi-trigonal or trigonal networks that are two-dimensionallynoncentrosymmetric. Substitutional variations on thephenyl moieties that were expected to maintain or to perturb thistrigonal network have been explored. Molecularnonlinearities have been measured by Harmonic Light Scattering (HLS)experiments. Among the compoundsstudied, 2,4,6-triphenoxy-1,3,5-triazine, 1 adopts anoncentrosymmetric crystal structure with a measurableSHG powder signal. All these crystal structures are stabilized byweak intermolecular interactions such asherringbone, π···π, C−H···O, and C−H···Nhydrogen bonding. These octupolar molecules are moreisotropicthan the classical p-nitroaniline based dipolar NLOmolecules, and this is advantageous from the viewpoint ofpotential electrooptic applications.
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