STRUCTURAL AND SPECTRAL-ANALYSIS OF ORTHO-SUBSTITUTED AND META-SUBSTITUTED NITRAMINOPYRIDINE N-OXIDES

The X-ray structure of three nitraminopyridine N-oxide (NAPNO) crystal s have been determined out at room temperature. The following compound s have been studied: 2-nitraminopyridine N-oxide (2NAPNO), 3-nitramino pyridine N-oxide (3NAPNO) and a mixed crystal of 2NAPNO and the methyl amine (2NAPNOMA). Quantum-chemical semi-empirical methods were used to optimize them (PM3) and to evaluate their excited-state properties in the gas phase (GRINDOL-CI) as well in polar environments (GRINDOL-CI- VCM). Solvent dependence of the intensity ratio of charge transfer to the L-1(b) band in electronic absorption spectra of NAPNO compounds ha s been noticed. Contrary to 4-nitropyridine N-oxide derivatives, in th e NAPNO series an increase in charge transfer connected with increasin g displacement of the nitro group from the molecular plane has been ob served. (C) 1998 Elsevier Science B.V. All rights reserved.