Document Detail


Chiral bis(amino acid)- and bis(amino alcohol)-oxalamide gelators. Gelation properties, self-assembly motifs and chirality effects.
MedLine Citation:
PMID:  20062853     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Bis(amino acid)- and bis(amino alcohol)oxalamide gelators represent the class of versatile gelators whose gelation ability is a consequence of strong and directional intermolecular hydrogen bonding provided by oxalamide units and lack of molecular symmetry due to the presence of two chiral centres. Bis(amino acid)oxalamides exhibit ambidextrous gelation properties, being capable to form gels with apolar and also highly polar solvent systems and tend to organise into bilayers or inverse bilayers in hydrogel or organic solvent gel assemblies, respectively. (1)H NMR and FTIR studies of gels revealed the importance of the equilibrium between the assembled network and smaller dissolved gelator assemblies. The organisation in gel assemblies deduced from spectroscopic structural studies are in certain cases closely related to organisations found in the crystal structures of selected gelators, confirming similar organisations in gel assemblies and in the solid state. The pure enantiomer/racemate gelation controversy is addressed and the evidence provided that rac-16 forms a stable toluene gel due to resolution into enantiomeric bilayers, which then interact giving gel fibres and a network of different morphology compared to its (S,S)-enantiomer gel. The TEM investigation of both gels confirmed distinctly different gel morphologies, which allowed the relationship between the stereochemical form of the gelator, the fibre and the network morphology and the network solvent immobilisation capacity to be proposed. Mixing of the constitutionally different bis(amino acid) and bis(amino alcohol)oxalamide gelators resulted in some cases in highly improved gelation efficiency denoted as synergic gelation effect (SGE), being highly dependent also on the stereochemistry of the component gelators. Examples of photo-induced gelation based on closely related bis(amino acid)-maleic acid amide and -fumaramide and stilbene derived oxalamides where gels form by irradiation of the solution of a non-gelling isomer and its photo-isomerisation into gelling isomer are provided, as well as examples of luminescent gels, gel-based fluoride sensors, LC-gels and nanoparticle-hydrogel composites.
Authors:
Leo Frkanec; Mladen Zini?
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-12-03
Journal Detail:
Title:  Chemical communications (Cambridge, England)     Volume:  46     ISSN:  1364-548X     ISO Abbreviation:  Chem. Commun. (Camb.)     Publication Date:  2010 Jan 
Date Detail:
Created Date:  2010-01-11     Completed Date:  2010-03-12     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9610838     Medline TA:  Chem Commun (Camb)     Country:  England    
Other Details:
Languages:  eng     Pagination:  522-37     Citation Subset:  IM    
Affiliation:
Division of Organic Chemistry and Biochemistry, Laboratory for Supramolecular and Nucleoside Chemistry, Ruder Boskovi? Institute Bijenicka 54, Zagreb, Croatia.
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MeSH Terms
Descriptor/Qualifier:
Amides / chemistry*
Amino Alcohols / chemistry
Gels / chemistry*
Hydrogen Bonding
Models, Molecular
Molecular Conformation
Oxamic Acid / analogs & derivatives*
Photochemistry
Stereoisomerism
Chemical
Reg. No./Substance:
0/Amides; 0/Amino Alcohols; 0/Gels; 471-47-6/Oxamic Acid

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