Hydrogen-bonding interactions in acetonitrile oligomers using density functional theory method

Abstract

Hydrogen-bonding interaction in acetonitrile oligomers is studied using density functional theory method. Two types of hydrogen-bonded oligomers are considered viz. cyclic and ladder. Different levels are used to optimize the geometry of acetonitrile monomer and found that at B3LYP/aug-cc-pvtz level the geometrical parameters and vibrational frequencies are in agreement with the experimental determinations. The BSSE corrected total energies of acetonitrile oligomers show that the cyclic structures are more stable than the ladder and the hydrogen bonds in former are stronger than those in the latter. Many-body analysis approach was used to study the nature of interactions between different molecules in these oligomers. It is found that the contribution from many-body energies to the binding energy of a complex is different in cyclic and ladder structures. An increase and decrease in the energy per hydrogen bond with cluster size for the cyclic and ladder structures, respectively, indicates the positive and negative hydrogen-bond cooperativity, respectively.