Hartree-Fock and density functional studies on the molecular structure of ( E)-2-methoxy-4-[2-(4-nitrophenyl)ethenyl]-phenol

Abstract

Hartree-Fock (HF) and density functional theory (DFT) calculations have been carried out on the molecular structure of ( E)-2-methoxy-4-[2-(4-nitrophenyl)ethenyl]-phenol (MNEP) which has interesting non-linear optical properties. This compound is also known as 4-methoxy-3-hydroxynitrostilbene in the literature. We have performed geometry optimizations at the HF level with the STO-3G, 3–21G, 4–31G and 3–21 + + G(d) basis sets. DFT calculations with the hybrid functional B3LYP using the 3–21G basis set have also been carried out. The HF investigations show a twisted structure of MNEP, in which the planes of the two phenyl rings are twisted relative to each other, whereas the DFT calculations result in a planar conformation. The conjugation of the π-electrons throughout the molecule is described best by the B3LYP functional and is consistent with the experimental data. The dipole moment of MNEP and of similar molecules is more strongly influenced by the type of the various functional groups than by small variations of the angles between the planes of the two phenyl rings.