Structure and properties of hydrogen bonded complexes of pyridine-N-oxide and its derivatives

Molar Kerr constants and electric dipole moments of hydrogen bonded complex es that pyridine-N-oxide and its derivatives form with phenols are studied (a) experimentally, (b) by the vector/tensor addition scheme, and (c) by AM 1 and PM3 semiempirical quantum chemical methods. The data are used to esta blish the geometry of the complexes. It is shown that for a series of pyrid ine-N-oxide derivatives, the logarithm of the complex formation equilibrium constant correlates with the charge on the oxygen atom of the N-O group. A method to calculate the first and second complex formation constants based on the electric properties of the individual components of the complex is proposed. A relationship between the polarity of the hydrogen bond and the sum of the charges on the hydrogen and oxygen atoms forming the bond is est ablished for the complexes under study. (C) 1999 Elsevier Science B.V. All rights reserved.