Density functional theory study on the conformational behaviour of substituted banana-shaped mesogens with a central 1,3-phenylene unit


In the present study, the influence of the direction of ester linkage groups on the structural and electronic properties of the three-ring bent-core, bis(4-subst.-phenyl) 2-methyl-iso-phthalates molecules with a central 1,3-phenylene unit including 4-n-alkanoyl, 4-n-alkaoxyl and 4-n-alkayl terminal chains have been studied by density functional theory (DFT) calculations. The BP86/SVP level of theory has been adopted for all the computations. These computations were performed on the conformational behavior of the three-ring bent-core compounds in a systematic way. The relaxed rotation barrier with respect to the torsion angles φ1and φ2 where calculated. Moreover, replacement of terminal chains, alkanyl group by alkayloxy and alkayl groups, results a small rotational barrier with a difference of about 0.2-0.8 kcal.mol-1 in the height of the barriers, suggesting that the terminal chain have no effect on the relaxed barriers for these isomers. The dipole moment with respect to the torsion angle φ1 was also studied. The large differences in the dipole moments, can be seen as signs of their different phase behaviour and mesophase stability.