2-(1-PYRROLYL, DIAZOLYL, AND TRIAZOLYL)-SUBSTITUTED 5-NITROPYRIDINES FOR NONLINEAR-OPTICAL MATERIALS

2-Azolyl-5-nitropyridines (the generic name ''azoles'' is hereafter us ed for pyrrole, diazoles, and triazoles, and ''azolyls'' for any subst ituents derived from them) were examined from the viewpoints of the UV -vis absorption properties. the molecular hyperpolarizabilities (beta) , the second-harmonic generation (SHG) activities and the crystal stru cture compared with N-(4-nitrophenyl)azoles. In the azolyl-5-nitropyri dines, although an expected remarkable hypsochromic shift of the absor ption maxima (lambda(max)) was not observed, a hypsochromic shift of t he absorption edge (lambda(cutoff)) was observed. All of derivatives d iscussed in the present paper, except for 2-(3.5-dimethyltriazolyl)-5- nitropyridine (14), did not show any SHG activity. The inactive result s in SHG suggest that the displacement of benzene to pyridine causes a significant change in the molecular arrangement in the crystalline st ate. The phase-matchable property in the SHG of 14 is suggested by its crystal structure as well as an SHG experiment.