A ligand-chirality controlled supramolecular hydrogel.

We report a novel example of ligand-chirality finely controlled in situ supramolecular hydrogel formation based on the coordination of phenylalanine (Phe) to Cu(II) with higher selectivity over other metal ions. As decreasing both enantiomeric excesses (ee%) of ligand Phe towards its D- and L-forms, the gelation ability of Phe-Cu(II) supramolecular metallogelator was found to be weakened and eventually disappeared, which likely resulted from the stereoselectivity of the ligand Phe. Intermolecular hydrogen bonding, hydrophobic and/or pi-pi stacking interactions were also found to be essential for forming the metallogel. We believe that the present work can open up a new entry for developing novel and promising chiral sensing and recognition platforms, i.e. visually sensing chiral molecules by naked eyes due to the feature of a sol-to-gel transition induced smartly by varying the ligand chirality.