Hydrogen-bond induced surface core-level shift in pyridine carboxylic acids

Intermolecular hydrogen bonding in thick films of pyridine carboxylic acids (isonicotinic; picolinic and bi-isonicotinic acid) evaporated onto rutile TiO2(1 1 0) has been investigated with X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. These molecules are shown to be strongly H- bonded in the condensed phase, and a surface core-level shift is observed d ue to the presence of non-H-bonded nitrogen atoms in the surface layer. Den sity functional theory calculations are used to relate the experimental dat a to the proposed bonding configurations based on the surface termination o f the known equilibrium solid-state structure. A kinetic barrier, attribute d to the high degree of molecular orientation required for the formation of extended H-bonding networks, has also been investigated. (C) 2001 Elsevier Science B.V. All rights reserved.