DFT conformational study of five-ring bent-core mesogens with a central 1,3‐phenylene unit

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Muthanna Journal of Pure Sciences – MJPS

 

VOL.(3), NO.(2), 2016

Shatha Raheem Helal Alhimidi1, Muhsen Abood Muhsen Al-Ibadi2 and
Abbas H. Abo Nasria1
1 Department of Physics, College of Science, University of Kufa
2 Department of Chemistry, College of Science, University of Kufa

 

Abstract

The potential energy surfaces of the five-ring bent-core molecules with a central 1,3-phenylene unit,
including azobenzene with alkyloxy as terminal chains, has been investigated by using density functional theory (DFT). The PBE1PBE/6-31G(d,p) level of theory has been used for some computations in addition to the BP86 function, where used to study the influence of rotation of the connection groups. These computations were performed on the conformational behavior of the connection groups, included ester linkage group, N=N group and terminal OR group, of the five-ring bent-core compound in a systematic way. The relaxed rotation barrier with respect to the six torsion angles (φ1, φ2, φ3, φ4, φ5 and φ6) were calculated. It is interesting to note that the oxygen atoms of the linkage group, which are directly connected to the rings, give banana-shaped compounds with energy barrier by about
0.9 kcal mol-1 and high flexibility, whereas the ester group connected to phenyl ring by a carbon atom shows a high energy barrier by about 10.2 kcal mol-1 and a relatively limited conformational degree of freedom. The dependency of the Dipole moment on conformers with constraints to the torsion angle was studied.

Keywords: banana liquid crystals; bent-core mesogens, molecular structure and DFT calculations.


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