Guichao Kuang

Glycine-glutamic-acid-based organogelators and their fluoride anion responsive properties

Novel low-molecular-weight organogelators (LMOGs) 1 and 2 derived from glycine-glutamic-acids (GGA) based dipeptide were synthesized. The difference on the chemical structures between 1 and 2 resulted in some interesting variations on their gelling behavior and fluoride anion (F−) responsive properties. Gelator 1 could gel aromatic solvents effectively, while gelator 2 possessed excellent gelation ability in protic solvents. Upon the addition of 0.5 equiv. F−, the toluene gel of 1 transformed into solution due to the disruption of the intermolecular hydrogen-bonding, whereas the alcohol gel of 2 was stable and preserved even by introducing 20 equiv. F−. Interestingly, 2 could be regarded as an efficient receptor for F− in acetonitrile (MeCN) solution. After the addition of F−, the fluorescent emission band of 2 red-shifted from 360 to 420 nm with the emission intensity enhanced drastically; the intensity of the CD signal decreased and almost disappeared after addition of 2 equiv. F−. These changes were due to the conformational change and hydrogen-bonding interaction between urea groups and F−. The results indicated that GGA-based 1 and 2 might represent potential sensor materials for the naked-eye detection of F−.

Polymorphism of Amino Acid‐Based Dendrons: From Organogels to Microcrystals

There is a delicate balance for a low-weight molecule to behave as a gelator or crystal. The synthesis of two novel amino acid-based naphthalene-dendrons, Nap-G1 and Nap-G2 is described. Both dendrons display polymorphic properties in organic solvents. Nap-G1 developed a fibrous network with β-sheet architecture in cyclohexane but exhibited a spherulitic network in mixed solvents (chloroform/petroleum ether 1:5, v/v). On the other hand, Nap-G2 acted as an efficient organogelator in chloroform but formed crystalline fibers in relatively high polarity solvents (such as acetone and methanol). Combinations of characterizations have been employed to study the polymorphism.

Photoreversible dendritic organogel.

A photoreversible organogel made from dendrons was reported.