Synthesis and Gelation Behavior of a Pyrene-Containing Glucose Derivative

A pyrene-containing glucose derivative (PSDAPG) was synthesized and characterized. Its gelation behavior in 36 solvents was evaluated and the compound geled 16 of the solvents tested. Interestingly, PSDAPG was a super gelator for 1-decanol and its lowest gelation concentration (LGC) was 7.0x10(-4) g center dot mL(-1). PSDAPG was found to behave as a "bifunctional gelator" as it gels in both water and organic solvents. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (H-1 NMR) spectroscopy and fluorescence spectroscopy reveal that the gelator adopts different supramolecular network structures in different solvents. Additionally, hydrophobic and pi-pi stacking interactions exist between the pyrene structures of the gelator molecules. Hydrogen bonding between the glucose residues also plays a crucial role in the spontaneous formation of gel networks. Fluorescence emission spectra of PSDAPG in the solution state and in the gel state were characterized by monomer emission and excimer emission. Profiles of the two types of spectra were quite different. We found that the monomer emission increased and the excimer emission decreased as the gelation process proceeded. This indicates that formation of gel networks greatly suppresses the mobility of pyrene units in the gelator and results in lower excimer formation efficiency via Birks' scheme.