Environmentally responsive supramolecular systems are highly attractive for fundamental studies of complex structures and designing new functional materials. Herein, a new supramolecular motif bearing an active urea moiety and carboxylic acid groups is developed as a self-complementary molecule. It exhibits concentration-dependent dimerization in THF. Deprotonation by base induces self-assembly into dimer in polar solvents such as the hydrogen bonding competitive solvent DMSO. The formation of a hydrogen bonded, dimeric structure was confirmed in the gas phase by LC-MS and in pure DMSO solution by DOSY-<sup>1</sup>H NMR spectroscopy. The molecule exists as a zwitterion in solid state by X-ray diffraction analysis. Reversible switching between monomer and dimer was achieved in the polar solvent by sequential addition of Et<sub>3</sub>N as base and TFA as acid. The fluorescence signal was used to monitor the self-assembly process, giving three cycles without significant signal loss. Noticeably, this molecule not only represents a new class of hydrogen bonding directed supramolecular motif but also offers the potential to grow more sophisticated molecular structures with use of the available metal coordination site. It was demonstrated by single crystal diffraction that a tetramer is formed upon coordination with silver nitrate, retaining the hydrogen bonding dimeric structure. This enhanced branching ability opens a new pathway to self-assemble more sophisticated supramolecular structures from a very basic structure unit.

pH-switched self-assembly of a self-complementary supramolecular motif in polar solvent

255th National Meeting (2018)

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