FT-TR, UV-VISIBLE AND X-RAY STUDIES OF COMPLEXES OF PYRIDINE N-OXIDESWITH PENTACHLOROPHENOL

The crystal structure of the 4-methoxy-2,6-dimethylpyridine N-oxide pe ntachlorophenol complex has been determined by X-ray analysis. The O . .. O distance is 2.439(6) Angstrom, the OHO angle is 152.3 degrees 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 p olarity (epsilon from 2.27 to 37.5) show a broad absorption. The broad absorption shows weak dependence upon solvent polarity and is classif ied as type (ii). UV spectra show that in the investigated complexes p rotons are not transferred from the phenol to the N-oxides. Formamide (epsilon = 111) is a much stronger proton acceptor than the pyridine N -oxides. Pentachlorophenol in formamide is converted to the phenolate ion.