Ej. Maclean et al., STRUCTURAL AND DYNAMIC PROPERTIES OF HYDROGEN-BONDING IN A TETRAHEDRAL ARRANGEMENT OF METHANOL MOLECULES - A THEORETICAL INVESTIGATION, Chemical physics letters, 225(1-3), 1994, pp. 273-279
The crystal structure of triphenylmethanol contains tetramers of triph
enylmethanol molecules, in which the four oxygen atoms are arranged ap
proximately at the comers of a tetrahedron with the C-O bonds along th
e threefold symmetry axes of the tetrahedron. The O ... O distances in
the tetrahedron are consistent with the suggestion that the tetramer
is held together by 0-H ... 0 hydrogen bonding. To understand the stru
ctural and dynamic properties of this arrangement, we consider a model
system comprising a structurally analogous tetramer of methanol molec
ules. In the theoretical approach adopted, hydrogen bonding is treated
as a purely electrostatic interaction, with the molecular charge dist
ributions described using distributed multipoles. The optimum position
s of the hydrogen atoms involved in hydrogen bonding have been determi
ned, and dynamic properties of the hydrogen bonding arrangement have b
een probed. In the configuration with lowest electrostatic energy, eac
h oxygen atom of the methanol tetramer receives one hydrogen bond, wit
h the hydrogen atoms lying close to the 0 ... 0 edges of the tetrahedr
on. Dynamics of the hydrogen bonding arrangement, via rotation of the
methanol molecules about their C-0 bonds, involves correlated rotation
of all four methanol molecules to interconvert configurations of equa
l energy. The barrier for this motion is approximately 5 kJ mol-1.