Molecular structures, hydrogen bonding and electrostatic interactions of 3-(2-bromo-pyridinium)-propionic acid and 3-(pyridinium)-pivalic acid halides

Intra- and intermolecular interactions and the conformations of 3-(2-bromo- pyridinium)-propionic acid bromide (1) and 3-(pyridinium)-pivalic acid chlo ride (2) have been studied by X-ray diffraction and theoretically. In these complexes, Br- and Cl- anions are H-bonded to the COOH group and interact electrostatically with the positively charged nitrogen atoms of neighbourin g molecules. To analyse these interactions theoretically, the structures of monomers and dimers in various configurations were optimized by PM3 and BL YP/6-31G(d,p) methods. The analysis confirmed the vital role of both the H- bonds and electrostatic interactions (intra- and intermolecular) for the mo lecular conformation and the ionic aggregation in the solid state. (C) 2001 Elsevier Science B.V. All rights reserved.