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Second-harmonic generation studies of chiral organic salts

TitleSecond-harmonic generation studies of chiral organic salts
Publication TypeJournal Article
Year of Publication1998
AuthorsBorecka-Bednarz, B, Bree, AV, Patrick, BO, Scheffer, JR, Trotter, J
JournalCanadian Journal of Chemistry-Revue Canadienne De Chimie
Volume76
Pagination1616-1632
Date PublishedNov
Type of ArticleArticle
ISBN Number0008-4042
Keywordsasymmetric, chiral organic salts, crystal structures, DERIVATIVES, INDUCTION, MOLECULAR-CRYSTALS, NONLINEAR OPTICS, NONLINEAR-OPTICAL-MATERIALS, second-harmonic generation, SOLID-STATE PHOTOCHEMISTRY
Abstract

Second-harmonic generation in the solid state is restricted to materials that crystallize in non-centrosymmetric space groups. Unfortunately, the vast majority of solids crystallize in centrosymmetric space groups and are therefore SHG-inactive. The requirement for solid-state asymmetry is addressed in a new series of organic salts. The acid p-nitrophenylglycine, SHG-inactive due to its centrosymmetric (P1) packing, was coupled to six optically pure amines to form salts and (or) complexes that, by virtue of their chiral counterion, crystallized in non-centrosymmetric space groups. The 1064 nm output from a Nd:YAG laser produced 532 nm second-harmonic generation from each of the six salts, with, three of the salts producing second-harmonic intensities at least an order of magnitude greater than that of our standard, urea. X-ray crystallographic analysis was carried out on five of the six salts, and an attempt was made to rationalize the second-harmonic intensity of each of these five salts based on the orientation of its molecular charge-transfer axis in the unit cell and on its chromophore density.

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