FIELD EFFECTS ON DIHYDROGEN BONDED SYSTEMS

To investigate the hydrogen transfer within a crystal by means of the crystal field, the effect of an external electric field over three dif ferent proton equilibrium systems has been studied with ab initio meth ods. The equilibria chosen were: (1) from neutral molecules dihydrogen bonded to cation/H-2/anion complexes, (2) from neutral/H-2/neutral co mplexes to charged molecules dihydrogen bonded and (3) from neutral an d charged molecules dihydrogen bonded to charged/H-2/neutral complexes . The electric field was applied along the molecular axis increasing f rom 0.00557 to 0.03342 au. At the theoretical level, it has been found that by applying an external field the transfer of H atoms between tw o heavy atoms is possible. Thus, a coordinated hydrogen molecule becam e a dihydrogen bond in the case of Li+... H-H ... F-. Oppositely, a di hydrogen bonded complex became two molecules coordinated to molecular hydrogen in the case of the H3N+-H ... H-BH3- system. (C) 1997 Elsevie r Science B.V.