No abstract

Solvent molecules significantly affect the supramolecular self-assembly, for example, in forming solvent-bridged hydrogen bonding networks. Even small changes in solvent composition can have dramatic impact on supramolecular assembly. Herein, we demonstrate the use of trace solvents (as low as 0.04%) to tune the morphology and consequent functions of supramolecular nanostructures based on an aromatic peptide bola-amphiphile. Specifically, perylene bisimide-(di)glycine-tyrosine (PBI-[GY]) bola-amphiphile was shown to give rise to red-emitting nanofibers when assembled in water, while exposure to trace organic solvents such as tetrahydrofuran (THF) and others via solvent-evaporation followed by aqueous assembly gave rise to white-light-emitting nanospheres. Differential hydrogen bonding between water (donor and acceptor) and THF (acceptor only) impacts supramolecular organization, which was verified using a density functional theory (DFT) simulation. The tunable consequent surface hydrophobicity was utilized in staining the cytoplasm and membrane of cells, respectively. The trace-solvent effect achieved through evaporation-dissolution provides a methodology to mediate the morphologies and consequent functions for supramolecular biomaterials controlled by the self-assembly pathway.

Echoed with the sustainable chemistry concept, the developments of highly efficient and practical asymmetric catalysts have been and continue to be the fore of organic synthesis. Functionalized chiral ionic liquids (FCILs), which combine the green credential of ionic liquids [1] and the catalytic principles of modern asymmetric catalysis, have recently appeared as such a type of asymmetric catalyst. Following the initial work of Howarth [2] and Seddon; [3] the applications of FCILs have moved beyond the use as chiral additives, chiral reagents, or chiral inducing reaction media, [4] and now have reached the stage of asymmetric catalysts.[5] However, the promising potentials of FCILs as asymmetric catalysts still remain largely underdeveloped at present and the current successes have been primarily confined to the reactions like Michael additions and aldol reactions. As such, in our continuing efforts in exploring this type of catalA C H T U N G T R E N N U N G ysis, [5d-f, n] we have sought new reaction development by taking advantage of the intrinsic properties of ionic liquids. Herein, we report the first FCIL-catalyzed enantioselective S N 1 type alkylation of cyclic ketones, in which the ionic liquid moieties are found to be critical for both the catalytic activity and stereocontrol.The catalytic asymmetric direct a-alkylation reaction of carbonyl compounds has long been a daunting challenge in asymmetric catalysis and synthesis.