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Gelation-driven selection in dynamic covalent CC/CN exchange†
Jean-Marie Lehn
Chemical Science Pub Date : 09/06/2017 00:00:00 , DOI:10.1039/C7SC02827J
Abstract

Knoevenagel barbiturate derivatives bearing long alkyl chains were proven to form organogels in suitable solvents based on supramolecular interactions. Their reaction with imines allows for component exchange through C[double bond, length as m-dash]C/C[double bond, length as m-dash]N recombination. The effect of various parameters (solvents, chain length, and temperature) on the C[double bond, length as m-dash]C/C[double bond, length as m-dash]N exchange reaction has been studied. Mixing Knoevenagel compound K and imine I-16 in a 1 : 1 ratio generated a constitutional dynamic library containing the four constituents K, I-16, K′-16, and I′. The reversible exchange reaction was monitored by 1H-NMR, showing marked changes in the fractions of the four constituents on sol–gel interconversion as a function of temperature. The library composition changed from statistical distribution of the four constituents in the sol state to selective amplification of the gel forming K′-16 constituent together with that of its agonist I′. The process amounts to self-organization driven component selection in a constitutional dynamic organogel system undergoing gelation. This process displays up-regulation of the gel-forming constituent by component redistribution through reversible covalent connections.

Graphical abstract: Gelation-driven selection in dynamic covalent C [[double bond, length as m-dash]] C/C [[double bond, length as m-dash]] N exchange
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