Chiral effect on the self-assembly of chiral molecules synthesized from cholesterol

One predesigned chiral steroid base compound cholesteryl 4-(carbonyloxy) 4-(hexyloxyl) benzoate (CCH*) and two achiral compounds with various alkyl chain length oxalyl acid N',N'-di(4-(hexyloxy)benzoyl)hydrazide (AG6) and oxalyl acid N',N'-di(4-(undecyloxy)benzoyl)-hydrazide (AG11) have been successfully synthesized. Formation of asymmetric self-assembled constructions via self-assembly of achiral molecules in chiral environment was investigated. Due to steric hindrance, CCH* could not form gel in any kind of organic solvents. On the other hand, AG6 and AG11 formed achiral gels in many kinds of solvent. The results suggest that polarity, side branch and intermolecular forces are the key factors for the gelation. Temperature-dependent H-1 NMR analysis of the fabricated gels show that van der Waals forces and pi-pi interactions are key factors leading to self-assembly of molecules result in three-dimensional networks. In addition, CCH* was used as a chiral dopant added into achiral compounds forming asymmetric self assembled constructions. The results indicate that doping of CCH* into achiral gelators giving a chiral environment leads to the formation of helical constructions. The fabricated asymmetric constructions were confirmed using circular dichroism (CD) spectroscopy and small angle X-ray scattering (SAXS). (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.