title: Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism.
abstract: Vibrational circular dichroism (VCD) spectroscopy was applied to gelation by a chiral low-molecular mass weight gelator, N,N'-diperfluoroalkanoyl-1,2-trans-diaminocyclohexane. Attention was focused on the winding effects of (-CF2 )n chains on the gelating ability. For this purpose, a series of gelators were synthesized with perfluoroalkyl chains of different length (n = 6-8). When gelation was studied using acetonitrile as a solvent, the fibrils took different morphologies, depending on the chain length: twisted saddle-like ribbon or helical ribbon from fibril (n = 6) and a helical ribbon from platelet (n = 8). The signs of VCD peaks assigned to the couplet of C=O stretching and to the C-F stretching were also dependent on n, indicating that a gelator molecule changed conformation on elongating perfluoroalkyl chains. A model is proposed for the aggregation modes in fibrils. Chirality 28:361-364, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Graduated of Science and Engineering, Ehime University, Matsuyama, Japan.
authors.forename: Hisako
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Chemistry, Ochanomizu University, Tokyo, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yajima
authors.affiliation: Department of Chemistry, Toho University, Chiba, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yamagishi
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D002942:Circular Dichroism / Q000379:methods*; D003514:Cyclohexylamines / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008968:Molecular Conformation; D013237:Stereoisomerism; D014732:Vibration
chemical_list: D000097:Acetonitriles; D003514:Cyclohexylamines; D005782:Gels; C032159:acetonitrile
keywords: chiral gelator; perfluoroalkyl chains; supramolecular; vibrational circular dichroism