The electronic properties of pyridine-oxide and some of its substituted derivatives have been studied at the ab initio LCGO-SCF level. The results for pyridine-1-oxide and nitro-pyridine-oxide are in good agreement with experiment. As regards 3-methyl-4-nitro-pyridine-1-oxide (POM), the dipole moment of 0.22 or 0.48 D obtained for the two C(s) conformations considered in this work do not confirm the value suggested by the analysis of the electronic density maps obtained from cristallographic data (3.5 D). The polarizabilities ( = 81 a.u.) and the hyperpolarizabilities (beta(z) = 1050 a.u.) are the first ones obtained theoretically. Although they cannot be compared with experimental results because of the difficulty of measuring them, they allow to understand why POM is an organic material interesting for optoelectronics
