The first hemicucurbit[n]uril macrocycles were described in 2004, and since then a series of functionalised hemicucurbit[n]uril derivatives have been prepared and studied. The original hemicucurbit[n]urils suffer from sparse solubility, which limits their applications in supramolecular chemistry. Recent progress in the synthesis of a range of derivatives such as the biotin[n]urils, the bambus[n]urils, and the cyclohexylhemicucurbit[n]urils have enabled studies of the supramolecular chemistry of the hemicucurbituril system, both in water and in a range of organic solvents. In contrast to the popular cucurbit[n]uril macrocycles that are state‐of‐the‐art hosts for cations, the hemicucbit[n]urils host anions. Herein we provide a survey of the literature covering the syntheses of the hemicucurbituril derivatives and their supramolecular chemistry.

We present a simple procedure to make an augmented reality app to visualize any chemical 3D model. The molecular structure may be based on crystallographic data or from computational modeling. This guide is made in such a way that no programming skills are needed, and the procedure uses free software and provides a way to visualize 3D structures that are normally difficult to comprehend in the 2D space of paper. The process can be applied to make a 3D representation of any 2D object, and we envisage the app to be useful when visualizing simple stereochemical problems, when presenting a complex 3D structure on a poster presentation or even in audio-visual presentations. The method works for all molecules including small molecules, supramolecular structures, MOFs, and biomacromolecules.

Fully aromatic helicenes with more than one pitch‐length are illustrious synthetic targets with potential applications in advanced optical devices and nano‐electronics. The task of extending the length of fully conjugated helicenes past one pitch length is challenging. Now, the synthesis of a series of azaoxa[7]‐, [10]‐, and [13]helicenes is described. The synthesis is based on iterative oxidative furan formation between 3,6‐dihydroxycarbazoles and/or 2‐naphthols. The flexibility of the presented method allows the convenient and scalable synthesis of symmetric, unsymmetrical, and asymmetric homo‐chiral structures. The [13]helicenes can be synthetically functionalized both at the termini and the periphery. The full range of helicenes were characterized using NMR and optical spectroscopy (UV/Vis, fluorescence, and CD) along with single‐crystal X‐ray crystallography. The enantiomers of the [13]helicenes are the longest optically pure helicenes isolated to date.

No abstract

Binding of anions using macrocyclic structures with a nonpolar interior using the CH···anion interaction as the recognition motif has gained popularity in the past few years, and such receptors often rely on a subtle interplay between enthalpic and entropic factors. For these types of receptors solvation of both the anion and the binding pocket of the macrocyclic host play important roles in the overall energetic picture of the binding event. Systematic chemical modifications of synthetic receptors that are able to bind anions in a variety of solvents is an important tool to gain understanding of the factors that determine the supramolecular chemistry of anions. Here we present the chiral macrocyclic structure biotin-l-sulfoxide­[6]­uril as a host molecule that binds anions in both water and in organic solvents. Biotin-l-sulfoxide­[6]­uril is prepared in a highly diastereoselective one-pot synthesis from the macrocycle biotin[6]­uril. We compare the binding properties with that of biotin[6]­uril, also studied in acetonitrile and in aqueous buffer at neutral pH. The biotin-l-sulfoxide­[6]­uril generally exhibits stronger recognition of anions in acetonitrile, but weaker binding in water as compared to the biotin[6]­uril macrocycle. We have studied the binding events using a combination of NMR spectroscopy, isothermal titration calorimetry (ITC), and computational methods.

We present a high‐yielding intramolecular oxidative coupling within a diazadioxa[10]helicene to give a dihydro‐diazatrioxa[9]circulene. This is the first [n]circulene containing more than eight ortho‐annulated rings (n>8). The single‐crystal X‐ray structure reveals a tight columnar packing, with a proton from a pendant naphthalene moiety centred directly above the central nine‐membered ring. This distinct environment induces a significant magnetic deshielding effect on that particular proton as determined by 1H NMR spectroscopy. The origin of the deshielding effect was investigated computationally in terms of the NICS values. It is established that the deshielding effect originates from an induced paratropic ring current from the seven aromatic rings of the [9]circulene structure, and is not due to the nine‐membered ring being antiaromatic. UV/Vis spectroscopy reveals more efficient conjugation in the prepared diazatrioxa[9]circulene compared to the parent helical azaoxa[10]helicenes, and DFT calculations, including energy levels, confirm the experimental observations.

The thermally induced O → S and O → Se migration reactions facilitate the rearrangement of O-benzyl thio- and selenocarbamates [BnOC(═X)NMe] (X = S or Se) into their corresponding S-benzyl thio- and Se-benzyl selenocarbamates [BnXC(═O)NMe] (X = S or Se). A series of substituted O-benzyl thio- and selenocarbamates were synthesized and rearranged in good yields of 33-88%. The reaction rates are higher for substrates with electron-donating groups in the 2 or 4 position of the aromatic ring, but the rearrangement also proceeds with electron-withdrawing substituents. The rearrangement follows first-order reaction kinetics and proceeds via a tight ion pair intermediate consisting of the benzylic carbocation and the thio- or selenocarbamate moiety. Computational studies support these findings.

<p>We present a simple procedure to make an augmented reality app to visualize any 3D chemical model. The molecular structure may be based on data from crystallographic data or from computer modelling. This guide is made in such a way, that no programming skills are needed and the procedure uses free software and is a way to visualize 3D structures that are normally difficult to comprehend in the 2D space of paper. The process can be applied to make 3D representation of any 2D object, and we envisage the app to be useful when visualizing simple stereochemical problems, when presenting a complex 3D structure on a poster presentation or even in audio-visual presentations. The method works for all molecules including small molecules, supramolecular structures, MOFs and biomacromolecules.</p>