Low Molecular Weight Gelator Responds to Chemical Stimuli

Abstract

Tris-urea 1 functioned as a low molecular weight gelator for a variety of polar organic solvents including acetone, and methanol. Brief sonication of a mixture of 1 and an appropriate solvent gave a stable translucent gel. An acetone gel of 1 became a homogeneous solution in response to the addition of anions. The minimum amount of anion necessary for the gel-sol transition was peculiar to the anion species. A linear relationship was demonstrated between the amount of anion and the total binding constant of 1 with the anion. Re-gelation occurred by addition of boron trifluoride etherate (BF3•OEt2) and irradiating ultrasound of the acetone solution of 1 and F–. Re-gelation caused by BF3•OEt2 was specific for solutions containing F– or AcO–; solutions containing Cl–, Br–, or I– remained unchanged after the same treatment.