The conclusion is inevitable: Increasing stabilization of an anionic transition state with increasing π-acidity of the catalyst is observed; thus, anion-π interactions can contribute to catalysis.

The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion−π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion−π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol–1 are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 105 M–1. Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of “anion−π catalysis.” In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis–Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π–π interactions are not very important for anion−π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion−π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the catalysts, i.e., the existence of anion−π catalysis. Preliminary results on the general significance of anion−π catalysis beyond the Kemp elimination are briefly discussed

Flexible chain-like molecules can adopt various conformations, but fabrication of complex and higher-order architectures by chain networking or coiling is still a difficult task in organic chemistry. As the degree of freedom increases, the large entropy loss impedes conformation and orientation fixing. Here we report oligo (3,3-dimethylpentane-2,4-dione)s as flexible and shapable carbon chains with many carbonyl groups for chemical modification. Polycarbonylated chains of various lengths are synthesized by terminal-selective silylation and oxidative coupling reactions using silver(I) oxide. We use reactions of 1,3-diketones and 1,4diketones to reduce the chain length and to induce favourable conformations. When the chains are treated with hydrazine, all the carbonyl groups are converted to imine groups, resulting in the formation of multidentate ligands. Finally, a two-dimensional sheet-like structure and a cylindrical assembly are generated by respectively networking and coiling the carbon chains, with the aid of metal coordination.

The self‐assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal–acetylene π‐coordination of a tripodal ligand (L) with acetylene spacers gave an M3L2 double‐propeller motif (M=CuI or AgI), which dimerized into an M6L4 interlocked cage (M=CuI). Higher (M3L2)n oligomers were also selectively obtained: an M12L8 truncated tetrahedron (M=CuI) and an M18L12 truncated trigonal prism (M=AgI), both of which contain the same double‐propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.

The cooperation of weak acetylene π-coordination and relatively strong metal–heteroatom coordination has emerged as a promising strategy for the construction of highly complex but well-ordered nanostructures. Here, we report the formation of an (M3L2)8 truncated cube (M = AgI) via the oligomerization of an M3L2 subunit stabilized by the secondary π-coordination of an acetylene spacer. This large framework cannot be obtained directly from its components (M and L) but is instead formed by counteranion exchange (BF4 – to NO3 –) of the presynthesized smallest oligomer, the dimeric (M3L2)2 cage. Single-crystal X-ray diffraction analyses revealed that the cubic framework of (M3L2)8 exhibits a π-coordination-supported highly entangled structure, which is formally constructed via alternation of the cubic corners and edges with helical M3L2 subunits and double lines with two twists, respectively. This observation enabled us to understand the complicated structures of the series of (M3L2) n polyhedral cages (n = 2, 4, 6, 8) as a fundamentally new type of molecular entanglements based on trifurcate motifs, which can be obtained selectively by adjusting the self-assembly conditions.

Bring it on: Organic chemistry on surfaces and in solution is not the same; this study offers a perfect example that small changes (from 27 to 35°; see graphic) can result in big consequences. Strained cyclic disulfides from asparagusic, but not lipoic acid, are ideal for growing functional architectures directly on surfaces; for the substrate-initiated synthesis of cell-penetrating poly(disulfide)s in solution, exactly the contrary is true.

Eindeutige Hinweise belegen eine erhöhte Stabilisierung des anionischen Übergangszustands mit zunehmender π‐Acidität des Katalysators. Dies bedeutet, dass Anion‐π‐Wechselwirkungen an Katalysen beteiligt sein können.

We have synthesized a series of triarylamine-cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by (1) H NMR and UV/Vis spectroscopy that their supramolecular self-assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable-temperature polarizing optical microscopy (VT-POM), variable-temperature X-ray diffraction (VT-XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar- or columnar-packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self-assemblies as electroactive materials from solution to mesophases.