engleski

Crystal and gelation properties of naphthalene bioconjugates

Low molecular mass gelators have been intensively researched in the past decade due to their ease of preparation and potential application in the field of soft and optical materials, transportation media, and as active media for organic reactions and catalysis. Of special interests are chiral gelators where amplification of chiral or luminescent properties can be achieved via gelation. We have successfully applied amino acid substituted benzene derivatives bearing phosphine moiety as ligands in Rh-catalyzed enantioselective hydrogenation reactions ; 3 it was shown that the enantioselectivity is strongly dependant of the amino acids used as well as the benzene substitution (meta- or para-). As an expansion of our research towards the field of soft materials, here we present an ongoing work on amino acid disubstituted naphthalene bioconjugates where solid state and gelation properties are influenced by small modifications of the molecule. Several crystal structures of bioconjugates were obtained. All compounds exhibit hydrogen bonding in their but no π-π stacking was observed. In the case of nonchiral glycine methyl ester derivative, two polymorphs were obtained by slow evaporation of different solvent solutions. It was shown by means of polycrystaline X-ray diffraction that in THF, a single phase is formed whilst in ethanol, both phases are present. The two polymorphs differ only in their characteristic torsion angles of the amide group. All derivatives were tested as gelators in various organic solvents. The results have shown that alanine derivative (Figure 1) with C6-aliphatic chains exhibit super-gelation of nonpolar aromatic solvents.

amino acids ; supramolecular chemistry

nije evidentirano