Cyclohexane-based low molecular weight hydrogelators: a chirality investigation

Arianna Friggeri, Cornelia van der Pol, Kjeld J C van Bommel, André Heeres, Marc C A Stuart, Ben L Feringa, Jan van Esch

Onderzoeksoutput: ArticleAcademicpeer review

Samenvatting

Seven new 1,3,5-cyclohexyltricarboxamide-phenylalanine derivatives were synthesized in order to investigate the effect of the amino acid chirality on the gelating properties of these small molecules in water. Gelation tests have shown that enantiomerically pure homochiral 1,3,5-cyclohexyltricarboxamide-L-phenylalanine is a non-hydrogelator as it crystallizes from water, whereas the heterochiral derivatives with either two L-phenylalanine moieties and one D-phenylalanine (LLD), or vice versa (DDL), are very good hydrogelators. Concentration-dependent gel-to-sol transition-temperature (T(gs)) curves for LLD or DDL gels show a sigmoidal behaviour, which is in contrast to the logarithmic curves generally observed for gels derived from low molecular weight gelators (LMWGs). Such sigmoidal behaviour can be related to interactions between fibre bundles, which give rise to intertwined bundles of fibres. Transmission electron microscopy (TEM) images of LLD and DDL gels show a network of thin, unbranched, fibre bundles with diameters of 20 nm. Right-handed twisted fibre bundles are present in the LLD gel, whereas left-handed structures can be found in the DDL gel. Each bundle of fibres consists of a finite number of primary fibres. Gels consisting of mixtures of gelators, LLD and DDL, and nongelators (LLL or DDD) were investigated by means of T(gs) measurements, CD spectroscopy and TEM. Results show that the incorporation of nongelator molecules into gel fibres occurs; this leads to higher T(gs) values and to changes in the helicity of the fibre bundles. Furthermore, it was found that peripheral functionalization of the homochiral derivatives LLL or DDD by means of a second amino acid or a hydrophilic moiety can overcome the effect of chirality; this process in turn leads to good hydrogelators.

Originele taal-2English
Pagina's (van-tot)5353-5361
TijdschriftNature Chemistry
Volume11
Nummer van het tijdschrift18
DOI's
StatusPublished - 5 sep 2005

Keywords

  • chemie

Vingerafdruk Duik in de onderzoeksthema's van 'Cyclohexane-based low molecular weight hydrogelators: a chirality investigation'. Samen vormen ze een unieke vingerafdruk.

Citeer dit