Molecular knots remain difficult to produce using the current synthetic methods of chemistry because of their topological complexity. We report here the near-quantitative self-assembly of a trefoil knot from a naphthalenediimide-based aqueous disulfide dynamic combinatorial library. The formation of the knot appears to be driven by the hydrophobic effect and leads to a structure in which the aromatic components are buried while the hydrophilic carboxylate groups remain exposed to the solvent. Moreover, the building block chirality constrains the topological conformation of the knot and results in its stereoselective synthesis. This work demonstrates that the hydrophobic effect provides a powerful strategy to direct the synthesis of entwined architectures.

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In this Communication, the structures of the d-and l-amino acid naphthalenediimide (NDI) derivatives in Scheme 1 were inadvertently interchanged. The correct scheme is shown below. Scheme 1. Amino acid NDI derivatives. Boc = tert-butyloxycarbonyl, Bzl = benzyl, Trt = trityl.

A new type of neutral donor-acceptor [2]-catenane, containing both complementary units in the same ring was synthesized from a dynamic combinatorial library in water. The yield of the water soluble [2]-catenane is enhanced by increasing either buildingblock concentrations or ionic strength, or by the addition of an electron-rich template. NMR spectroscopy demonstrates that the template is intercalated between the 2 electron-deficient naphthalenediimide units of the catenane.dynamic combinatorial chemistry ͉ molecular recognition W e report here the spontaneous assembly of a donoracceptor (D-A) [2]-catenane from a dynamic combinatorial library (DCL) in water. Unusually, this is a D-A catenane that contains the electron-deficient and electron-rich aromatic moieties in the same ring. Owing to their complex topology and the resulting synthetic challenge, mechanically interlocked molecules such as catenanes have captivated chemists for a long time (1). With advances in the efficient templated synthesis of these interlocked structures, applications of these interesting molecules have been found in molecular electronic devices, such as switches, motors, color displays, and molecular memory (2-5).Conventional catenane synthesis relies on the use of noncovalent interactions to preorganize precursors in a suitable configuration that favors the formation of an interlocked structure, employing an irreversible, kinetically controlled chemical reaction as the final catenating step (for recent examples, see 6-9). The recent rise of dynamic covalent chemistry (10) using reversible chemical reactions under thermodynamic control has led to an increasing number of catenane syntheses that are either designed to lead to a particular structure (for recent examples, see 9, 11-19) or result from unpredictable dynamic combinatorial selection (20,21). The advantage of either of these dynamic strategies is the possibility of recycling un-interlocked components, hence increasing the yield of the desired structure.Interactions between electron-rich aromatics, such as dialkoxynaphthalene (DN) and tetrathiafulvalene (TTF), and electron deficient aromatics, like naphthalenediimide (NDI) and paraquat, have been extensively used in the preparation of catenanes (9,22,23). The vast majority of these catenane constructions rely on kinetically controlled reactions. Some examples of thermodynamically controlled syntheses of these structures include the neutral [2]-catenanes featuring zincpyridine coordination (24) and alkene metathesis as the ringclosing reactions (25). More recently, Stoddart and coworkers reported the iodide-catalyzed self-assembly of paraquat-based cationic D-A [2]-(16) and [3]-catenanes (14) from separate -donor and -acceptor rings using thermodynamically controlled nucleophilic substitution. Most of the examples of D-A catenane syntheses depend on a preformed, -rich crown ether ring containing electron-donor units, and the subsequent formation of new electron-deficient rings followed by catenation. Hence, the resulting catenanes...

A homochiral naphthalenediimide-based building block forms in water a disulfide library of macrocycles containing topological isomers. We attempted to identify each of these isomers, and explored the mechanisms leading to their formation. The two most abundant species of the library were assigned as a topologically chiral Solomon link (60% of the library, as measured by high-performance liquid chromatography (HPLC)) and a topologically achiral figure eight knot (18% by HPLC), competing products with formally different geometries but remarkably similar 4-fold symmetries. In contrast, a racemic mixture of building blocks gives the near-quantitative formation of another new and more stable structure, assigned as a meso figure eight knot. Taken together, these results seem to uncover a correlation between the point chirality of the building block used and the topological chirality of the major structure formed. These and the earlier discovery of a trefoil knot also suggest that the number of rigid components in the building block may translate into corresponding knot symmetry and could set the basis of a new strategy for constructing complex topologies.