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In this work, we demonstrate that the centrosymmetric eight-membered supramolecular ring R2 2 (8) that is formed upon dimerization of benzoic acids has a marked tendency to establish π−hole interactions with electron-rich atoms. We have used the Cambridge Structural Database to demonstrate the preference of carboxylic acid dimers to form donor−acceptor interactions involving π−holes located at the C atoms above and below the molecular plane. Moreover, we have carried out DFT calculations (PBE0-D3/def2-TZVP) to investigate the geometric and energetic features of these interactions and how they are affected by the substituents of the aromatic ring. Finally, as an example we report the synthesis and X-ray characterization of a solvate of gallic acid with dioxane, where two molecules of dioxane are located above and below the eight-membered supramolecular ring, forming two symmetrically equivalent O•••C π−hole interactions.

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Shelf stable, chiral-at-metal, D(3) symmetric, 3:1 complexes of lanthanide (III) triflate salts are easily available by complexation with binolam (3,3'-diethylaminomethyl-2,2'-dihydroxy-1,1'-dinaphthalene) 1 or binolamo (3,3'-diethylaminooxymethyl-2,2'-dihydroxy-1,1'-dinaphthalene) 2 ligands. The resulting compounds 3Ln and 4Ln are isostructural, as demonstrated by their spectroscopic data, and possess an arrayed acid-base LABABB network. Complexes are kinetically labile, and in solution undergo hydrolysis by water. The lanthanum complex derived from binolam, i.e., (Delta,S,S,S)- (binolam)(3).la(OTf)(3)3La was found to be the most active catalyst in promoting direct nitroaldol reactions upon aldehydes and trifluoromethyl ketones, thereby giving rise to secondary nitroalcohols and tertiary alpha-trifluoromethyl-beta-nitroalcohols, respectively, with high ee in both cases. Enantiomerically enriched tertiary nitroalcohols were easily reduced to the corresponding aminoalcohols having a quaternary asymmetric carbon without loss of enantiomeric purity.

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Mononuclear triple-stranded helicate complexes ML 3 (M = Sc 3+ , La 3+, Sm 3+ , Yb 3+ ) were self-assembled and structurally characterized by NMR spectroscopy and high-resolution mass spectrometry. The solid-state structure of the ytterbium complex was determined by X-ray crystallography. The core lanthanide metal ion was replaced quantitatively by three so-

The cover picture shows a stereoselective mononuclear triplestranded helicate complex. Three chiral binaphthol N-oxide derivative ligands are coordinated to a trivalent ytterbium metal atom. This very stable and symmetrical structure was obtained by spontaneous self-assembly. NMR spectroscopy and X-ray crystallography were used for unambiguous characterisation. In the picture, the greenish sphere indicates the ytterbium atom and the larger spheres indicate the oxygen atoms. All those ligands, depicted in different shades to highlight the helical effect, are identical. Details are discussed in the article by M. Capó et al. on p. 3405 ff.