Synthesis and structural study of a novel nonlinear optical material: the tolane derivative ethyl 2-(4-benzyloxyphenylethynyl)-5-nitrobenzene-1-carbamate

Abstract

We have synthesized the tolane derivative ethyl 2-(4-benzyloxyphenylethynyl)-5-nitrobenzene-1-carbamate1, a promising material for nonlinear optics. Compound 1 has several crystal forms and we have characterized their structural properties by X-ray diffraction. One of the three forms, which is crystallized from a strong polar solvent, has a non-centrosymmetric structure and is ca. ten times as strong a second-harmonics generator as meta-nitroaniline. A hydrogen bond is found to perform an important role in forming the non-centrosymmetric geometry, which is necessary for a nonlinear optical crystal.