Deuterated Derivatives of 3,5-Dimethyl-1-(4-nitrophenyl)pyrazole for Nonlinear Optical Materials

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Abstract
A weak absorption of laser light by a nonlinear optical crystal causes a noticeable temperature rise in the crystal. Such absorption may undesirably shift the reflactive indices (some optical characteristics) of the crystal. 3,5-dimethyl-1-(4-nitrophenyl)pyrazole [DMNP], an excellent nonlinear optical material, was deuterated in order to suppress its absorption in the 1 μm wavelength region. Three deuterated deriatives were synthesized; their crystal structures were identical with that of DMNP. The deuteration of the pyrazole part including the two methyl moieties proved to be more effective than deuteration of the phenyl part (benzene ring) with regard to a reduction of the IR absorption. A good correlation was confirmed between the temperature elevation under laser irradiation and IR absorption.