The structure of benzene in liquid ammonia: the search for N-H··pi hydrogen bonding

Hydrogen bonding systems are characterised by short X-H···A interactions. Such bonds have traditionally been associated with atoms such as X = O, N, S and A = O, N, S and halide, and have a strong electrostatic component arising from the highly dipolar nature of X-H bonds. Beyond the traditional hydrogen bonding interaction, the highly polarised nature of the X-H bond allows the electron rich pi-system of an aromatic ring to act as a hydrogen bond acceptor. Such O/N/C-H···pi interactions have been found in the solid state for both small molecule and biomolecule crystals and are now recognised as contributing significantly to molecular recognition and protein folding. In this proposal we will investigate the structure of benzene dissolved in liquid ammonia. By exploiting extensive isotopic substitution and the extended Q-range on NIMROD we will investigate the structural environment around the aromatic, and in particular the detailed nature of the N-H···pi hydrogen bonding and the 3-dimensional distribution of the solvation shell.