I CRYSTAL GROWTH AND CHARACTERIZATION OF NLO ACTIVE ORGANIC INCLUSION COMPOUNDS. Jürg Hulliger, Olaf König, Vera Kramer-Hoss, Institute of Inorg., Analyt. and Physical Chemistry, University of Berne, Switzerland.
Design of efficient organic nonlinear optical (NLO) materials attempts a molecular hyperpolarizability ßzzz up to a value close to 10'000 10-40m4/V and seeks for an orientation of ßzzz- axes that optimizes either frequency doubling (SHG) or the electro-optic (EO) effect of macroscopic I crystals [1-3].
On account of a low yield [1-3] of crystal structures providing a parallel alignment of dipoles (max. EO effect), recent interest focused on the packing of NLO molecules along parallel channels of inclusion type lattices [4]. When compared to other host materials [5], perhydrotriphenylene (PHTP) worked out to be ideally suited [6,7] to include a variety of linearly shaped NLO entities of the A-[[pi]]-D type (A, D: acceptor, donor group, respectively; [[pi]]: thiophene, stilbene, polyphenyl, polyacetylene). SHG powder tests revealed that PHTP-(A-[[pi]]-D) inclusion formation produces polar materials at a yield of around 75% that is 3 times higher than found for corresponding single component systems. Crystals of PHTP-(A-[[pi]]-D) were grown by (i) controlled isothermal evaporation of 2-butanone or paraldehyde, (ii) the temperature difference technique, and (iii) by sublimation [8].
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