FT-IR, UV—visible and X-ray studies of complexes of pyridine N-oxides with pentachlorophenol

Abstract

The crystal structure of the 4-methoxy-2,6-dimethylpyridine N-oxide·pentachlorophenol complex has been determined by X-ray analysis. The O ··· O distance is 2.439(6) Å, the OHO angle is 152.3° and the hydrogen-bonded proton is close to the phenol molecule. The FT-IR spectra of pentachlorophenol complexes with some substituted pyridine N-oxides in the solid state and seven aprotic solvents of different polarity (ϵ from 2.27 to 37.5) show a broad absorption. The broad absorption shows weak dependence upon solvent polarity and is classified as type (ii). UV spectra show that in the investigated complexes protons are not transferred from the phenol to the N-oxides. Formamide ( ϵ = 111) is a much stronger proton acceptor than the pyridine N-oxides. Pentachlorophenol in formamide is converted to the phenolate ion.