Solvent-Assisted Tyrosine-Based Dipeptide Forms Low-Molecular Weight Gel: Preparation and Its Potential Use in Dye Removal and Oil Spillage Separation from Water.

Low-molecular weight gelators (supramolecular, or simply molecular gels) are highly important molecular frameworks because of their potential application in drug delivery, catalysis, pollutant removal, sensing materials, and so forth. Herein, a small dipeptide composed of -(-butoxycarbonyl)pentafluoro-l-phenylalanine and O-benzyl-l-tyrosine methyl ester was synthesized, and its gelation ability was investigated in different solvent systems. It was found that the dipeptide was unable to form gel with a single solvent, but a mixture of solvent systems was found to be suitable for the gelation of this dipeptide. Interestingly, water was found to be essential for gelation with the polar protic solvent, and long-chain hydrocarbon units such as, petroleum ether, kerosene, and diesel, were important for gelation with aromatic solvents. The structural insights of these gels were characterized by field-emission scanning electronic microscopy, atomic force microscopy, Fourier transform infrared analysis, and X-ray diffraction studies, and their mechanical strengths were characterized by rheological experiments. Both of the gels obtained from these two solvent systems were thermoreversible in nature, and these translucent gels had potential application for the treatment of waste water. The gel obtained from dipeptides with methanol-water was used to remove toxic dyes (crystal violet, Eriochrome Black T, and rhodamine B) from water. Furthermore, the gel obtained from dipeptide with assistance from toluene-petroleum ether was used as a phase-selective gelator for oil-spill recovery.