Analysis of pair interaction in a bipolar mesogen 4‐(4‐hydroxylbutyloxy)‐4′‐cyano‐biphenyl: A comparative study based on semiempirical and DFT methods

Structure of 4‐(4‐hydroxylbutyloxy)‐4′‐cyano‐biphenyl (H4CBP) molecule has been optimized using density functional B3LYP with 6‐31G (d) basis set taking crystallographic geometry as input. Using the optimized geometry, electronic structure of the H4CBP molecule has been evaluated on the basis of semiempirical methods and DFT calculations. Intermolecular interaction energy between a pair of H4CBP molecules has been evaluated by using Rayleigh–Schrodinger perturbation theory modified with multicentered multipole expansion method for the electrostatic part while dispersion and repulsion terms have been calculated using Kitaigorodskii formula. The results obtained through semiempirical and DFT calculations have been compared for various interacting conditions, viz.: (a) stacking, (b) in‐plane, and (c) terminal interactions. A comparative analysis of the results has been carried out with a view to examine suitability of different methods to study molecular aggregations in moderately large organic systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011