1 research outputs found
Intermolecular Hydrogen Bonding and Molecular Orbital Distortion in 4‑Hydroxycyanobenzene Investigated by X‑ray Spectroscopy
Electronic
structure of 4-hydroxycyanobenzene in the gas phase,
thick films, and single crystals has been investigated by X-ray photoemission
spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy
(NEXAFS). We have used resonant photoemission spectroscopy (RESPES)
to identify the symmetry and atomic localization of the occupied and
unoccupied molecular orbitals for the free molecule. Upon condensation
into a thick film, we find XPS energy shifts in opposite directions
for the oxygen and nitrogen core levels, consistent with the formation
of an intermolecular hydrogen bond. This interaction is also accompanied
by a significant spatial distortion of the lowest unoccupied molecular
orbital that is displaced from the nitrogen atom, as indicated by
the RESPES measurements. Thick films and single crystals display the
same dichroism in polarization dependent NEXAFS, indicating that the
intermolecular hydrogen bonding also steers the molecular assembly
into a preferred molecular orientation