Chiral induction of helical mesophase by amphiphilic chlorin e6 derivatives and their metal complexes: Effect of chiral and achiral aliphatic chains

Abstract

An experimental and theoretical study of structure and properties of chiral amphiphilic chlorin e6 13(N)-methylamide-15-methyl,17-alkyl esters (17-pentadecyl 1 and 17-phytyl 2) and their Ni complexes (Ni-1 and Ni-2) and their helical twisting efficiency in liquid crystal were carried out. Quantum chemical simulation of their structure was performed, the adequacy of which was established by comparing the calculated and experimental UV/Vis, CD, 1H and 13C NMR spectra as well as optical rotation angles. Low values of g-factors of dissymmetry for macroheterocycle (MHC) with the phytol substituent were experimentally revealed. The reason for this effect, associated with the transfer of the chirality from the stereogenic centers of the substituent to macrocyclic chromophore in the associate, was established by quantum-chemical calculation. Using polarization microscopy, the formation of chiral nematic phases was detected by doping a mixture of cyanobiphenyls with macroheterocycles 1, 2, Ni-1 and Ni-2. The values of the clearance temperature and helical pitch were measured, the slopes of phase diagrams β and helical twisting power (HTP) were calculated. The orientation order parameters of dopants in liquid crystal (LC) were determined by polarization spectroscopy. The dielectric properties of LC–MHC systems were studied within the chiral nematics and isotropic phases, and the values of the Kirkwood’s correlation factors were calculated. Using quantum chemical simulation of MHC solvates, the features of the influence of aliphatic chains structure and complex formation on the physical properties of induced mesophases were established.