Langmuir, Vol.27, No.7, 3945-3951, 2011
Solvent-Induced Helix Superstructure in Achiral Dumbbell-Shaped Hydrazine Derivatives
We studied hydrogen-bonding assemblies in a series of dumbbell-shaped hydrazine derivatives, namely oxalyl N',N'-bis(3,4-dialkoxybenzoyl)-hydrazide (BFH-n, n = 4, 6, 8, 10) and oxalyl N',N'-dibenzoyl-hydrazide (FH-0). It has been demonstrated that NH-1 protons of BFH-n precipitated from tetrahydrofuran (THF) or dimethylformamide (DMF) were involved in intramolecular H-bonding to form 6-membered rings. Meanwhile, NH-2 protons of BFH-n precipitated from THF formed intermolecular hydrogen bonds with C=O groups of neighboring molecules, while NH-2 protons of BFH-n precipitated from DMF formed intermolecular hydrogen bonds with C=O group of neighboring DMF molecules. C=O, -CH3, and -CH groups of DMF molecules participated in multiple intermolecular hydrogen bonds with the -N-H and -C=O groups of FH-0 molecules in single-crystals formed in DMF, leading to a double helix morphology with a pitch of 24.2 angstrom along the c direction. Both left- and right-handed helical micrometer-length ribbons with nonuniform helical pitches were observed in an achiral BFH-10 xerogel precipitated from DMF.