Benzene triimide (BTI, or mellitic triimide) is a C 3-symmetric backbone with a highly electron-deficient, extended π surface and three easy functionalization sites. Here, we report the first BTI-based cage composed of two face-to-face BTIs pillared by three m-xylylene spacers and efficient and selective binding of azide through cooperative anion−π interactions. The cage was easily synthesized in two steps from benzene triimide. Crystal structures showed that the two BTI planes can be separated at about 5–6 Å and form a well-defined electron-deficient cavity. Among a series of anions tested, the cage was found able to bind N3 –, SCN–, and I–. In particular, the binding toward N3 – is very strong (K a = 11098 ± 46 M–1) and highly selective, over 150 and 250 times higher than SCN– and I–, respectively. The control single BTI, however, showed only very weak binding (K a < 5 M–1). The crystal structure showed that N3 – is tightly trapped within the cavity through multiple, very short anion−π interactions. The slow enter–release of N3 – from the cavity was observed in the NMR. The charge-transfer and electron-transfer character of the interactions was also discussed.

A triangular prism cage 2 with benzene triimide (BTI) as the bases, 2,7-naphthalene dimethyl as the supporting pillars was designed and synthesized efficiently. The two parallel BTI planes constitute a cavity of 7.58 Å which allows inclusion of anions of various sizes. Cage 2 showed so far the strongest binding affinity to a series of polyhedral (tetrahedral and octahedral) anions including PF 6 -(24651 M -1 ), ClO 4 -(28234 M -1 ), CH 3 SO 3 -(30571 M -1 ), BF 4 -(31613 M -1 ) and HSO 4 -(84623 M -1 ). The obtained eleven crystal structures of 2⸧Xcomplexes with different anions demonstrated that multiple and cooperative anion- interactions contribute synergistically to the strong complexation. The series of complex structures systematically suggested that cage 2 is a good, general tool for probing anion- binding motifs that have only been predicted in theoretical calculations. For anions of triangular (NO 3 -) and polyhedral (BF 4 -, ClO 4 -, PF 6 -) shapes, the as-predicted most stable anion- binding motifs with charge-neutral  systems were experimentally observed for the first time.

Realizing anion−π interaction induced self-assembly with charge-neutral π receptors as building components is extremely challenging. We designed and synthesized a series of bisoxacalix[2]arene[2]triazines 7−11 in which two macrocyclic motifs are linked in diverse branching angle and rigidity. Crystal structures showed the use of rigid linkers is able to control the orientation of the two macrocyclic cavities. The interplay between the two cavities was revealed by binding studies of 8−11 with chloride in solution. Whereas 180°-and 120°branched hosts 8 and 9 possess dual complexation ability, 60°-branched and flexibly linked hosts 10 and 11 only form 1:1 complex with chloride. Association and self-assembly of these bismacrocyclic building units with dianionic naphthalene-1,5-disulfonate were systematically investigated. The formation of oligomeric self-assemblies and large aggregates in solution was suggested by 1 H NMR titrations, concentration-and temperature-variable 1 H NMR, diffusion-ordered spectroscopy (DOSY), ESI-MS, and dynamic light scattering (DLS). The anion−π induced long-distance self-assembly with coherent particle formation was revealed by SEM, TEM, cryo-TEM, and AFM techniques. The systematic studies allowed us to draw the conclusion that the dianion served to bridge the initial host aggregates through anion−π interactions and was responsible for the coherent particle formation. The cavity orientation of the bismacrocycle components was found to have a significant influence on the coherent particle morphology.

Radical pimers are the simplest and most important models for studying charge-transfer processes and provide deep insight into p-stacked organic materials. Notably, radical pimer systems with magnetic bi-or multistability may have important applications in switchable materials, thermal sensors, and information-storage media. However, no such systems have been reported. Herein, we describe a new pimer consisting of neutral N-(n-propyl) benzene triimide ([BTI-3C]) and its anionic radical ([BTI-3C] À C) that exhibits rare magnetic multistability. The crystalline pimer was readily synthesized by reduction of BTI-3C with cobaltocene (CoCp 2). The transition occurred with a thermal hysteresis loop that was 27 K wide in the range of 170-220 K, accompanied by a smaller loop with a width of 25 K at 220-242 K. The magnetic multistability was attributed to slippage of the p-stacked BTI structures and entropy-driven conformational isomerization of the side propyl chains in the crystalline state during temperature variation.

Summary of main observation and conclusion Herein, we report an efficient one‐pot condensation of maleimide derivatives in the presence of acetic acid and water to afford a series of benzene triimides (BTIs). The structure, physicochemical properties and electrochemistry behavior of BTIs were studied by means of X‐ray crystallography, UV‐Vis spectra, cyclic voltammetry and differential pulse voltammetry. Owing to the planar structure and unique electron‐deficient nature, BTIs can self‐assemble into different motifs including nanorod, nanotube, nanobrick and cross‐linked structure depending on different N‐substituents. The origin for different self‐assemblies was ascribed to the intermolecular lone pair‐π interaction or a balance of lone pair‐π and π‐π stacking.

Chiral amphiphilic oxacalix[2]arene[2]triazine derivatives 1-3 bearing l-prolinol moieties were synthesized. The self-assembly behavior of the chiral macrocyclic amphiphiles was investigated. SEM, TEM, and DLS measurements demonstrated that 1 formed stable vesicles (size of ∼90 nm), whereas 2 and 3 formed micelles. As monitored by DLS, vesicles composed of 1 showed selective response to the chiral anions (2S, 3S)-2,3-dihydroxysuccinate (d-tartrate), S-mandelate and S-(+)-camphorsulfonate over their enantiomers. DFT calculations revealed that the enantioselectivity arises from cooperative anion-π interactions and hydrogen bonding between the chiral electron-deficient cavity and the organic anions.

Manipulation of the emerging anion–π interactions in a highly cooperative manner through sophisticated host design represents a very challenging task. In this work, unprecedented tetrahedral anion–π receptors have been successfully constructed for complementary accommodation of tetrahedral and relevant anions. The synthesis was achieved by a macrocycle‐directed approach by using large macrocycle precursors bearing four reactive sites, which enabled a kinetic‐favored pathway and afforded the otherwise inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three‐dimensional cavity surrounded by four electron‐deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF4−, ClO4−, H2PO4−, HSO4−, SO42− and PF6− was revealed by ESI‐MS and DFT calculations. Crystal structures of ClO4− and PF6− complexes showed that the anion was nicely encapsulated within the tetrahedral cavity with up to quadruple cooperative anion–π interactions by an excellent shape and size match. The strong anion–π binding was further confirmed by negative ion photoelectron spectroscopy measurements.

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