RES2INS: A graphical interface for the SHELX program suite

RES2INS runs under the MS-DOS operating system and allows the user to view graphically the results of successive SHELX structure solution and refinement runs. In addition, the structural model can be edited in a user-friendly manner and these changes can be carried through to a new SHELX instruction file. The program is menu driven and extensive use is made of the mouse for the facilitation of operations on individual atoms.</p

Non-covalent interactions exert extraordinary influence over conformation and properties of a well-known supramolecular building block

At low pH, and in the presence of 4,4A-bipyridine, psulfonatocalix[4]arene crystallizes in the 1,3-alternate conformation rather than the expected cone conformation and exhibits remarkable stability. © 2001 Royal Society of Chemistry.</p

Molecular graphics: From science to art

The evolution of molecular graphics is briefly discussed. The utility of simplified representations of complex molecular assemblies is illustrated with several examples from the authors' previously published works.</p

Inclusion chemistry of cyclotetracatechylene

The synthesis and X-ray crystal structures of the first inclusion complexes of cyclotetracatechylene (CTTC, 1) are reported. Crystals grown from a dimethylformamide (DMF) solution of 1 contain a total of six DMF molecules per CTTC unit (1·6DMF, 5) whilst crystals obtained from methanol in the presence of pyridine vapour form as a 1:2:2 complex (1·2pyridine· 2methanol, 6). Hydrogen-bonded interactions between host and guest(s) play an important role in the molecular structure and, in the case of 6, a terminated eleven-atom hydrogen bonded chain is observed.</p

Supramolecular stabilization of N2H7+

The cation N2H7+ has been stabilized in a largely hydrophobic supramolecular environment and characterized in the solid state. The cation is situated in the bowl-shaped cavity of calix[4]arene. All of the hydrogen atoms are clearly discernible owing to high-quality X-ray data as well as lack of disorder and symmetry-imposed ambiguity. It appears that electrostatic interactions play a critical role in stabilizing the structure. Copyright © 2002 American Chemical Society.</p

An intermolecular (H2O)10 cluster in a solid-state supramolecular complex

Chemical self-assembly is the process by which 'programmed' molecular subunits spontaneously form complex supramolecular frameworks. This approach has been applied to many model systems, in which hydrogen bonds, metal- ligand coordination or other non-covalent interactions typically control the self-assembly process. In biology, self-assembly is generally dynamic and depends on the cooperation of many such non-covalent interactions. Water can play an important role in these biological self-assembly processes, for example by stabilizing the native conformation of biopolymers. Hydrogen- bonded (H2O) clusters can play an important role in stabilizing some supra- molecular species, both natural and synthetic, in aqueous solution. Here we report the preparation and crystal structure of a self-assembled, three- dimensional supramolecular complex that is stabilized by an intricate array of non-covalent interactions involving contributions from solvent water clusters, most notably a water decamer ((H2O)10) with a ice-like molecular arrangement. These findings show that the degree of structuring that can be imposed on water by its surroundings, and vice versa, can be profound.; Chemical self-assembly is the process by which 'programmed' molecular subunits spontaneously form complex supramolecular frameworks. This approach has been applied to many model systems, in which hydrogen bonds, metal-ligand coordination or other non-covalent interactions typically control the self-assembly process. In biology, self-assembly is generally dynamic and depends on the cooperation of many such non-covalent interactions. Water can play an important role in these biological self-assembly processes, for example by stabilizing the native conformation of biopolymers. Hydrogen-bonded (H2O)n clusters can play an important role in stabilizing some supramolecular species, both natural and synthetic, in aqueous solution. Here we report the preparation and crystal structure of a self-assembled, three-dimensional supramolecular complex that is stabilized by an intricate array of non-covalent interactions involving contributions from solvent water clusters, most notably a water decamer ((H2O)10) with an ice-like molecular arrangement. These findings show that the degree of structuring that can be imposed on water by its surroundings, and vice versa, can be profound.</p

Crystal and molecular structure of [H3O·18-crown-6]2-[ReCl6] isolated from a liquid clathrate medium

The crystal and molecular structure of [H3O·18-crown-6]2[ReCl6] 1 is reported. Crystal data for 1: trigonal, space group R 3, a = 13.857(2) Å, c = 10.154(2) Å, Dc = 2.85 g/cm3, Z = 3, Rf = 0.073, Rw = 0.064. The oxonium ion is observed to be crystallographically disordered lying 0.37 Å on both sides of the plane defined by the crown ether oxygen atoms. The anion resides on a crystallographic 3 position forming a slightly distorted octahedron.</p

Storage of methane and freon by interstitial van der Waals confinement

A known host-guest assembly, organized only by means of relatively weak dispersive forces, exhibits hitherto unappreciated thermal stability. The hexagonal close-packed arrangement of calix[4]arene contains lattice voids that can occlude small, highly volatile molecules. This host-guest system can be exploited to retain a range of freons, as well as methane, not only well above their normal boiling points, but also at relatively high temperatures and low pressures. The usually overlooked van der Waals interactions in organic crystals can indeed be used in a highly stable supramolecular system for gas storage.</p

Supramolecular assembly of well-separated, linear columns of closely-spaced C60 molecules facilitated by dipole induction

Co-crystallization of C60 with p-bromocalix[4]arene propyl ether results in a remarkably well packed structure; the calixarene molecules pack with their dipole moments aligned unidirectionally and the unusually close van der Waals contact between the C60 molecules is most likely a result of an opposing induced dipole.</p

Controlling molecular self-organization: Formation of nanometer-scale spheres and tubules

Amphiphilic polyhedron-shaped p-sulfonatocalix[4]arene building blocks, which have been previously shown to assemble into bilayers in an antiparallel fashion, have been assembled in a parallel alignment into spherical and helical tubular structures by the addition of pyridine N-oxide and lanthanide ions. Crystallographic studies revealed how metal ion coordination and substrate recognition direct the formation of these supramolecular assemblies. The addition of greater amounts of pyridine N-oxide changed the curvature of the assembling surface and resulted in the formation of extended tubules.</p