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Supramolecular hidden chirality of hydrogen-bonded (HB) networks of primary ammonium carboxylates was exposed by advanced graph set analysis from a symmetric viewpoint in topology. The ring-type HB (R-HB) networks are topologically regarded as faces, and therefore exhibit prochirality and positional isomerism due to substituents attached on the faces. To describe the symmetric properties of the faces, additional symbols, Re (right-handed or clockwise), Si (left-handed or anticlockwise), and m (mirror), were proposed. According to the symbols, various kinds of faces were classified based on the symmetry. This symmetry consideration of the faces enables us to precisely evaluate supramolecular chirality, especially its handedness, of 0D-cubic, 1D-ladder and 2D-sheet HB networks that are composed of the faces. The 1D-ladder and 2D-sheet HB networks generate chirality by accumulating the chiral faces in 1D and 2D manners, respectively, whereas 0D-cubic HB networks generate chirality based on combinations of eight kinds of faces, similar to the chirality of dice. [ABSTRACT FROM AUTHOR]

Quinine, one of Cinchona alkaloids, has been of great interest from medical, synthetic, and supramolecular viewpoints. However, unaccountably, the guest-free (GF) crystal of quinine containing no solvent or other molecules has not been reported for nearly three decades, although GF crystals of other Cinchona alkaloids, such as quinidine, cinchonidine, and cinchonine, are already known. In this study, we successfully revealed the crystal structure of quinine, which belongs to the P21 space group with the cell parameters of a=6.0587(1), b=19.2492(5), c=22.2824(7) Å, β=92.1646(11)°, and V=2596.83(12) Å3. Interestingly, the crystal has three crystallographically independent molecules in the cell ( Z′=3) that are connected through a N(quinoline)⋅⋅⋅HO hydrogen bond to form a pseudo three-two-fold (32) double-helical motif. The helical motif is completely different from those observed in GF crystals of other Cinchona alkaloids. Hierarchical comparison on the crystal structures of a series of Cinchona alkaloids including quinine clearly demonstrated that only small structural differences of a molecule, particularly the position of the vinyl group, cause a significant variety of assembly manner in the crystalline state. There have been no reports systematically demonstrating such steric effect in crystals of Cinchona alkaloids, and, therefore, the present system contributes to the design of desired functional crystal structures. [ABSTRACT FROM AUTHOR]

A twofold helix (21 helix) is an essential motif in approximately 70 % of organic crystals. Although handedness of 21 helix has not been discussed from a mathematical viewpoint, we noticed that the handedness can be defined by considering the molecular shape and manner of assembly. Herein we propose the supramolecular-tilt-chirality (STC) method to define the handedness, and illustrate it by way of some examples. We believe that establishment of the systematic rules for supramolecular chirality will contribute to the progression of supramolecular chemistry and material science. [ABSTRACT FROM AUTHOR]

Advanced graph set analysis has been proposed by incorporating a concept of symmetry into conventional graph set analysis. Based on the advanced graph set analysis, handedness determinations were demonstrated on supramolecular hidden chirality of three types of hydrogen‐bonded networks, 0D‐cubic, 1D‐ladder, and 2D‐sheet networks, by characterizing the symmetric properties of their component ring‐type hydrogen‐bonded networks formed by primary ammonium carboxylates. For more details see the Full Paper by I. Hisaki, M. Miyata et al. on page 2478 ff. [ABSTRACT FROM AUTHOR]

Review: ca. 50 refs. [ABSTRACT FROM AUTHOR]