Chlorin e6 13(N)-methylamide-15,17-dimethyl ester and its nickel complex as the inducers of chiral nematic liquid crystals

Abstract

To search for new effective inducers of helical liquid-crystalline phases, chlorin e6 13 (N)-methylamide-15,17-dimethyl ester (MADMECl) and its nickel complex (Ni-MADMECl) were studied. An increase in the optical activity of the chlorin e6 derivative upon complexation with nickel, associated with a distortion of the macrocycle structure, was established by circular dichroism spectroscopy and quantum chemistry. The introduction of a macrocyclic complex into binary LC mixtures based on cyanobiphenyls (CB-2) and Schiff bases (SB-2), as well as the macrocyclic ligand MADMECl in CB-2, was shown to induce the formation of helical LC phases with high helical twisting power (maximum HTP = 409 μm−1 for the mixture CB-2 + Ni-MADMECl). The HTP decreases with an increase in the additive concentration. The assessment of the dopant influence on the LC thermal stability was carried out. The temperature dependences of the permittivity components of the studied liquid-crystalline solutions were obtained at different dopant concentrations. The relationship between the dielectric anisotropy and the helical pitch is established due to the 3D compensation of molecular dipoles. Quantum-chemical simulation of dopant-LC solvates was performed. The influence of the energy of intermolecular interaction on the efficiency of nematic phase twisting was ascertained. The contribution of supramolecular chirality to the process of chiral induction was detected.