Hydrogen bond and the structures of 2-, 3-and 4-biphenylmethanols

Density functional theory (B3LYP/6-31G*) is applied to calculate structures, energy, dipole moment, polarizability, frequencies of normal vibrations in the harmonic approximation and intensities in vibrational spectra of 2-, 3-, and 4-biphenylmethanol molecules and their H-complexes that can form in crystalline, amorphous, and liquid phases. Based on the analysis of simulation results, the effect of the position of a methanol group in the molecule on its vibrational spectrum is discussed. The structure forming role of a hydrogen bonds in biphenylmethanols and the possibility of realization of two polymorphic modifications in 2-biphenylmethanol are stated. These modifications are: metastable monoclinic, in which each of four molecules of the unit cell is a link of a chain H-associate; and stable triclinic, in which four molecules of the unit cell organize an H-complex in the form of a cyclic tetramer. It is found that crystalline samples of 3-and 4-biphenylmethanols consist of chain H-associates. A glass-like sample of 2BPhM being a mixture of H-complexes consisting of cyclic tetramers and chain associates contains crystalline nuclei of triclinic and monoclinic polymorphous modifications in the supercooled state. In a liquid sample of 2BPhm, chain H-associates and free molecules are realized.