Twin-Tapered Molecules Containing Bi-dihydrazine Units: Self-Assembly through Intermolecular Quadruple Hydrogen Bonding and Liquid Crystalline Behavior

We report on the synthesis and self-assembly of a new series of twin-tapered dihydrazide derivatives, oxalyl acid N‘,N‘-di(3,4,5-trialkoxybenzoyl)-hydrazide (FH-Tn). Results from 1H NMR diluting experiments in chloroform and temperature-dependent 1H NMR spectroscopy revealed that molecules exhibited a conformational change at concentrations lower than 255 μM, e.g., from intramolecularly H-bonded six-membered rings to five-membered rings in the monomer state upon concentrating. Measurements of 1H NMR diluting experiment, FTIR spectroscopy, and mass spectroscopy revealed that the FH-Tn self-assembled into supramolecular chains either in chloroform at concentrations greater than 255 μM or in bulk through intermolecular quadruple H-bonding. On the basis of the results of DSC, polarized optical microscopy, and wide-angle X-ray diffraction (WAXD), we assigned enantiotropic hexagonal and unknown columnar phases to FH-Tn (n = 6, 7, 8, 10).