New calix[4]arene phosphoryl derivatives have been synthesized, starting from a calix[4]arene (cone conformer) bearing four P(O)–H functional groups at the wide rim as synthon. Their binding properties towards trivalent lanthanide and actinide cations are investigated by complexation studies in methanol, and liquid–liquid extraction studies. The carbamoylmethylphosphine oxide and diphosphine dioxide derivatives display the ‘calixarene effect’, i.e., they are more efficient than their constitutive binding sites. The studies also reveal the importance of the attachment mode of CMPO-functions to the calixarene platform for the cation binding properties.

Recent advances in single crystal X-ray diffraction have allowed this technique to be used as a valuable tool for the analysis of hydrate structure and composition. With detailed analysis of guest disorder, not only are the guest positions clearly defined, but by using the cage occupancy as a free parameter it becomes possible to obtain estimates of hydrate composition from the absolute cage occupancies. In this way, it is found that the small cage in ethane hydrate is weakly occupied (∼5%), something not seen in previous NMR work. The tilt angle between the ethane C–C bond and the equatorial plane of the large cage was found to be 23°, in good agreement with the value of 25.2° found previously from NMR studies. For the structure H hydrate of methylcyclohexane and methane, methane fills both small cavities to about 80% occupancy. For the structure II hydrate of benzene and xenon, the orientation of benzene in the structure II large cage was located, and xenon was confined strictly to the small cage. Tetrahydropyran in structure II hydrate was shown to float in a boat conformation on the wall of the large cage. We also report lattice parameters for a number of structure II hydrates determined by single crystal diffraction. A rough trend of unit cell parameter with guest size or volume is illustrated, although it is not as yet clear if there are other correlating factors. Structural data are reported which demonstrate that single crystal X-ray diffraction is a powerful tool for the analysis of hydrate structure and composition. Graphic

The unique series of cubic metal–organic NbO-type polymers M(dbmCN) 2 (dbmCN=dibenzoylacetonitrile, M=Cu, Co, Ni, Mn, Fe) is presented. The series of compounds M(dbmCN) 2 (dbmCN=dibenzoylacetonitrile, M=Cu, Co, Ni, Mn, Fe) has been synthesized and structurally characterized. The compounds exhibit robust metal-organic framework of cubic symmetry, and are capable of clathration of small molecules.

In the solid state the cage formed by two triureidocalix[6]arene units contains two molecules of water. These two included guest molecules do not interact either with each other or with the inner cage surface.

New heteroditopic nickel(II) and copper(II) transition metal dithiocarbamate ion pair receptors that contain amide and crown ether recognition sites have been prepared via metal directed self-assembly. Preliminary coordination studies reveal that these systems bind group 1 metal cations and a variety of anions. With the ditopic nickel(II) receptor, bis benzo-15-crown-5 intramolecular sandwich complexation of potassium cation cooperatively enhances the recognition of acetate. Electrochemical investigations show the copper(II) receptor senses anions and cations via significant perturbations of the copper(II)/copper(III) dithiocarbamate redox couple. Graphic

The coordination polymer formed by the addition of zinc(II)chloride to 4′-(4‴-octyloxyphenyl)-4,2′-6′,4″-terpyridine (readily prepared using green chemistry principles) has been structurally authenticated using single crystal X-ray diffraction and microanalysis techniques. The polymeric network adopts a layered helical zigzag arrangement about a distorted tetrahedral Zn(II) centre, forming channels of inter-digitated alkyl chains.

Triethylene glycol-functionalized gold nanoparticles have been obtained by exchange reaction from dodecanthiolate-MPCs. 1 H NMR allowed to determine a 1:1 ratio of alkyl- to triethylene glycol-functionalized thiolates while TEM images showed an average diameter of 5.4±1.3 nm. Solution UV–vis spectra of this new material in different alcohols present a shift of the surface plasmon band which is in accord with Mie theory. This suggests that the presence of a protecting monolayer able to interact with the solvent does not affect the optical properties of the gold core. These functional MPCs show a acid-induced formation of clusters which is time dependent and whose effect on the optical properties of the aggregate is solvent dependent. Graphic

The objective of this study was to exploit multifunctional rigid-rod β-barrel ion channels for α-helix recognition by dipole-potential interactions in polarized membranes. Synthesis and evaluation of artificial β-barrel 1 characterized by p -octiphenyl ‘staves,’ leucine residues at the outer and histidine as well as, for the first time, arginine residues at the inner barrel surface are described. Internal arginines were introduced to recognize organic ions such as α-helical poly- l -glutamic acid (α-PLGA) passing through pores formed by barrel 1 at nanomolar concentrations. In unpolarized spherical bilayers (EYPC-LUVs), P -helical α-PLGA blocked pore 1 with a K D =150 nM at pH=4.5. As expected for a highly symmetric supramolecular host, a K D =100 nM determined for M -helical α-PDGA at pH=4.5 did not support substantial chiral guest recognition. Decreasing K D 's with increasing pH indicated that, in unpolarized bilayers, pore 1 recognizes anions (rather than α-helices). In polarized spherical membranes, the K D for α-PLGA at pH=4.5 dropped substantially to 13 nM at V ≈−150 mV. This experimental support for operational dipole-potential interactions indicates that α-PLGAs bind within active pores in transmembrane orientation with intravesicular N- and extravesicular C-termini. Independence on bilayer polarization for binding of random-coil PLGA at pH=5.5 corroborated that dipole–potential interactions account for α-helix recognition in polarized membranes. Graphic

The crystal structure of a copper(I) complex of styrene in the presence of a chiral, nonracemic bisbenzothiazine ligand has been determined. Comparisons are made between similar crystal structures reported in the literature. Graphic

Organic polyamine-based macrocycles have been at the centre of interest as receptors for anionic species for more than 30 years. A synopsis of methods for their synthesis as well as an overview of their anion binding properties is given. The species are categorized according to their charge and their special geometrical and binding features. Graphic

Abstract Steroid cyclophanes, having four steroidal moieties on a tetraazaparacyclophane skeleton, were designed and synthesized as a structural and functional hybrid of the macrocyclic hosts and the bile acid aggregates. The steroid cyclophanes exhibited molecular recognition behavior environmentally sensitive in various media. In aqueous solution, the host provided a three-dimensionally extended hydrophobic and chiral cavity for aromatic molecules with large binging constants and marked guest specificity. At the air–water interface, a steroid cyclophane bearing four cholate moieties performed a unique and drastic cavity conversion depending on the surface pressure, and the resulting monolayer assembly acted as an effective piezoluminescent molecular device. The steroid cyclophane embedded in lipid bilayer membrane behaved as an artificial cell-surface receptor, and the characteristic of the molecular recognition in aqueous solution was basically maintained even in the lipid membrane. When an enzyme was non-covalently fixed on the molecular assembly in the presence of copper(II) ions as a signal transmitter between the receptor and the enzyme, the signal transduction behavior in which a response of the molecular recognition of a signaling ligand by the steroid cyclophane was transmitted to an effector enzyme was observed.

A 2,5-diamidopyrrole-capped macrobicycle was synthesized and its chloride salt binding ability evaluated in polar and apolar organic solvents. X-ray crystal structures of the receptor and its sodium chloride complex were obtained and in the latter structure the salt is bound as a contact ion-pair.

X-Seed is a software tool for X-ray crystallographers and runs under any of the 32-bit Microsoft Windows operating systems including 95, 98, Millennium Edition, 2000 and XP. Many of its features are tailored to meet the needs of scientists interested in solid-state supramolecular chemistry. The two primary functions of the software are (i) to serve as a graphical interface to the SHELX-97 program suite, and (ii) to produce high-quality molecular graphics images. In addition to these features, many other useful functions are also implemented in order to facilitate the process of crystal structure solution, refinement, analysis and presentation. Graphic

Two sodium macrocyclic azaether complexes are reported. In both cases, the sidearms are attached to macroring nitrogen and derive from 4-(3-indolyl)butyric acid. These are the first alkali metal complexes of 15- or 18-membered ring crown amides. In both cases, dimer structures are observed by X-ray crystallographic analysis. Seven oxygen donors are involved in complexing Na+ in the 15-membered ring case, and a symmetrical dimer forms with the 18-membered compound. In the latter case, each Na+ ion is coordinated by 5 ether oxygens from each macrocycle and a carbonyl group from an adjacent macrocycle making Na+ 6-coordinate. In neither case does the counterion interact with the ring-bound cation.

This crystal structure study examines systematically the effect of guest size and guest substituents on the guest–host interactions in a number of simple p - tert -butylcalix[4]arene host–guest compounds. With increasing chain length, the guest conformation becomes increasingly complex, going from a simple all- trans (C6) to s-shaped (C8) and helical (C12) conformations. For Cl-substituted alkanes, the Cl atom is excluded from the deep cavity, again by the chain taking on complex conformations. However, the Cl atom can be forced into the deep cavity with rigid guests such as 1,4-dichlorobenzene. The results suggest that it is space filling rather than specific interactions that give these compounds stability, and that they should be properly described as clathrates rather than as stoichiometric host–guest materials.

Tris (5-acetyl-3-thienyl) methane (TATM) inclusion compounds with a wide variety of guest molecules have been studied by the techniques of solid-state 13 C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy (CP/MAS NMR), powder X-ray diffraction and differential scanning calorimetry (DSC). The approach taken was to study guests with the same hydrocarbon backbone but with different halogen substituents (F, Cl, Br, I) at selected sites on that backbone. From the multiplicities of the host signals in the 13 C CP/MAS NMR spectra, the number of TATM molecules in the crystallographic asymmetric unit was determined. Powder X-ray diffraction experiments allowed us to investigate structural isomorphism of TATM inclusion compounds with different guests. In most cases, TATM forms isomorphic structures with guests that have the same hydrocarbon backbone, but with different halogen substituents. This was illustrated in the case of cyclohexyl halide and methylene halide guests. On the other hand, TATM will form one type of structure with a guest that has smaller halogen substituents (e.g., F, Cl, Br), but a completely different structure with a guest that has larger halogen substituents (e.g., I). This was illustrated in the case of monohalobenzene, 2-halobutane and 1,3-dihalopropane guests. Differential scanning calorimetry experiments allow one to investigate thermal stabilities of inclusion compounds with different guests. The enthalpy of decomposition data show that TATM forms more stable inclusion compounds with guests that have smaller, more electronegative halogen substituents (for a given hydrocarbon backbone), and the stability decreases as the size of the halogen substituent increases.

Results from monolayer studies using the enantiomers of cholesterol ( nat - and ent -cholesterol) provide the first evidence that enantioselective interactions between sterols and lipids can affect the physical properties of cell membranes. During monolayer compression, the ability of nat - and ent -cholesterol to act as enantioselective templates for ordering lipid alkyl chains into their extended conformations is found to depend on the structure of the lipid. Force/area isotherms for the compression of dipalmitoylphosphatidylcholine ( l -DPPC) monolayers containing 10–60 mol% of either nat - or ent -cholesterol are not significantly different. Hence, there is no enantioselectivity for the ordering effect of cholesterol in these mixed films. By contrast, isotherms of egg yolk sphingomyelin (SPM) monolayers containing 20–40 mol% of either nat - or ent -cholesterol are clearly different indicating that enantioselective sterol–lipid interactions occur in these monolayers. Ent-cholesterol condenses egg yolk SPM monolayers more efficiently than does nat -cholesterol. At 30 mol%, where enantioselectivity is the greatest, the gaseous to liquid condensed phase transition starts at a mean molecular area of ∼48 A 2 /molecule for the ent -cholesterol/egg yolk SPM monolayer and at ∼55 A 2 /molecule for the nat -cholesterol/egg yolk SPM monolayer. Furthermore, Brewster angle microscopy shows that an additional phase is formed during compression of the 30 mol% ent -cholesterol/egg yolk SPM monolayers that is not formed during compression of the 30 mol% nat -cholesterol/egg yolk SPM monolayers. In a wider context, the results suggest that the physical properties of cholesterol–sphingomyelin rafts, cell membrane domains postulated to be important for the intracellular trafficking of proteins and as domains for plasma membrane proteins involved in cell-signaling pathways, are influenced by the absolute configuration of cholesterol.

The synthesis of epimers 6-deoxy-6-[ N - tert -butoxycarbony1-β-alanyl-( S )histidylamino]-β-cyclodextrin and 6-deoxy-6-[ N - tert -butoxycarbonyl-β-alanyl-( R )histidylamino]-β-cyclodextrin is reported. CD and NMR spectroscopy reveals that in aqueous solution these compounds are arranged in a ‘sleeping swan’ like conformation. H bonds between the NH of peptide bonds and the upper rim of CDs stabilize self-inclusion. The chirality of His influences the orientation of the self-included chain in the cavity, thus determining different properties for the two epimers.

Reaction of tetracyanoethylene (TCNE) with CoBr 2 in methanol produces a carbanion based coordination polymer [Co(OHMe) 4 {μ-(NC) 2 CC(O)OMe}]Br·MeOH 1 . The enclathrated methanol molecule is situated in a cavity directly above the planar dinitrile ligand. Reaction of TCNE with CoBr 2 in methanol produces a novel dicyano ester carbanion-based coordination polymer.