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

2-Azolyl-5-nitropyridines (the generic name ''azoles'' is hereafter used for pyrrole, diazoles, and triazoles, and ''azolyls'' for any substituents 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 structure compared with N-(4-nitrophenyl)azoles. In the azolyl-5-nitropyridines, although an expected remarkable hypsochromic shift of the absorption maxima (lambda(max)) was not observed, a hypsochromic shift of the absorption edge (lambda(cutoff)) was observed. All of derivatives discussed in the present paper, except for 2-(3.5-dimethyltriazolyl)-5-nitropyridine (14), did not show any SHG activity. The inactive results in SHG suggest that the displacement of benzene to pyridine causes a significant change in the molecular arrangement in the crystalline state. The phase-matchable property in the SHG of 14 is suggested by its crystal structure as well as an SHG experiment.