Foldamer Organogels: A Circular Dichroism Study of Glucose-Mediated Dynamic Helicity Induction and Amplification

• Published in: Journal of the American Chemical Society Vol. 130; no. 40; pp. 13450 - 13459
• Main Authors: Cai, Wei, Wang, Gui-Tao, Du, Ping, Wang, Ren-Xiao, Jiang, Xi-Kui, Li, Zhan-Ting
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 08.10.2008; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Chloroform - chemistry; Circular Dichroism; Crystallography, X-Ray; Gelatin - chemistry; Gels - chemical synthesis; Gels - chemistry; Glucose - chemistry; Microscopy, Electron, Scanning; Models, Molecular; Molecular Structure; Organic Chemistry Phenomena; Physical Sciences; Science & Technology; Spectrophotometry; PHENYLENE ETHYNYLENE OLIGOMERS; RECOGNITION; SPECTROSCOPIC PROPERTIES; KINETICS; ORGANIC GELS; MOLECULAR-WEIGHT HYDROGELATORS; LYOTROPIC LIQUID-CRYSTALS; SELF-ORGANIZATION; AGGREGATION; SUPRAMOLECULAR CHIRALITY
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja8043322

This paper reports a systematic study of the dynamic process for the self-assembly of chiral organogels from achiral hydrogen bonded hydrazide foldamers by induction of chiral glucose. Six foldamers incorporated with six decyl chains and two benzene, naphthalene, anthracene, or pyrene units at the ends are revealed to strongly gelate apolar and polar solvents, including alkanes, arenes, esters, alcohols, and 1,4-dioxane. The gels are characterized by UV−vis, fluorescent, XRD, SEM, and AFM methods, based on which a dislocated “tail-to-tail” stacking pattern is proposed. Addition of octylated glucose considerably enhances the capacity of the foldamers to gelate apolar solvents due to strong complexation. The complexation also causes unique dynamic helicity induction in the gels, which is studied systematically by circular dichroism. The results are treated with the Avrami theory according to a reported method (J. Am. Chem. Soc. 2005, 127, 4336), which suggests that the gelation involves a nucleation−elongation mechanism. In addition, the “Sergeants and Soldiers” effect in the gel phase is also revealed.