Inclusion Host Research Articles

Phase separation and selective guest-host binding in multi-component supramolecular self-assembly on Au(111).

Bi-component supramolecular self-assembly of trimesic acid and benzenetribenzoic acid on Au(111) results in phase-separated mono-component porous structures. The pores of the two structures exhibit high selectivity in the binding of coronene molecules.

Comparison of cyclodextrins and urea as hosts for inclusion of drugs

Cyclodextrins have been extensively used for inclusion of various drugs for improvement of pharmaceutical characteristics of diverse nature. Numerous derivatives of cyclodextrins are currently available and are being subjected to continuous investigations. On the other hand, urea was previously being used as host for inclusion of straight chain linear compounds. However, development of a modified technique has opened flood gates for inclusion of non-linear drugs containing cyclic moieties. Cis-retinoic acid, nicorandil, vitamin E, amiloride, glipizide, enalapril maleate, simvastatin, lafutidine and ezetimbe are some of the drugs which have already been investigated for improvement of pharmaceutical characteristics. These characteristics include improvement of stability, content uniformity, dissolution profile and rheological behavior. Recently, pesticide-fertilizer combination has also been reported to serve the dual purpose of pesticide cum fertilizer and for improvement in safe handling and formulation characteristics. All FDA approved cyclodextrins are safe chemicals for human use within permissible limits. Urea is a component of normal physiological processes of body in human beings and other mammals. Urea is far cheaper when compared to cyclodextrins. Studies reveal that despite unique characteristics of urea like high solubility, non-toxicity, stability, inexpensiveness, biodegradability and easy availability, the use of urea as a host for inclusion of drugs has been grossly overlooked by researchers. Immense potential of urea as a host for inclusion of drugs need to be explored for improvement of pharmaceutical characteristics. The relative use of both cyclodextrins and urea as hosts for inclusion of drugs has been briefly reviewed in the present article.

Sources of fluids and material for gold and antimony mineralization in the Adychanskii ore region (East Yakutia, Russia)

The peculiarities of fluid inclusions; the O and C isotope composition of host rocks, vein minerals, and inclusions; and the S and Pb isotope composition of sulfides allowed us to distinguish two groups of fluids with a similar temperature, salinity, and source of the aqueous part produced upon metagenesis and mobilized during collisional events. Quartz-A precipitates from the CO2–H2O hydrocarbonate–Na fluid with a salinity of 7–10 wt % eq. NaCl at a depth of ∼6 km (290–340°C, 1550 bar). Regeneration of quartz (quartz-C), precipitation of quartz-B, and quartz-AB with carbonate and chlorite occurred at a depth from 3.5 to 1.5 km (250–380°C, 1250–900–350 bar) from CO2–CH4–N hydrous sulfate–hydrocarbonate Na–Mg fluids with Cl–, Ca, and K and a salinity of 5–10 wt % eq. NaCl, and a wide variety of impurities. The localization of veins in sinistral shear dislocations and strong heterogeneity in the P–T conditions allow us to explain the formation of fluid-2 by the postcollisional events.

Cucurbit[n]uril-based host–guest-metal ion chemistry: an emerging branch in cucurbit[n]uril chemistry

Cucurbit[n]urils (Q[n]s), a relatively new class of macrocyclic hosts with a rigid hydrophobic cavity and two identical carbonyl-fringed portals, have attracted much attention since the first member of the Q[n]-family, cucurbit[6]uril (Q[6]), was structurally identified in 1981 by Mock and co-workers. The interactions of the rigid cavities and negative portals of Q[n]s have resulted in the development of two almost mutually exclusive areas of study, namely Q[n]-based host–guest chemistry and Q[n]-based coordination chemistry. However, researches has revealed that Q[n]-based host–guest inclusion interactions may be influenced by metal ion coordination at the Q[n] portals, and in turn, coordination of metal ions at the Q[n] portals could be promoted by the formation of Q[n]-based inclusion host–guest complexes. Thus, this review provides an overview of related advances and achievements involving such a combination of Q[n]-based host–guest chemistry and Q[n]-based coordination chemistry, which could become an emerging branch, that is, Q[n]-based host–guest-metal ion chemistry. In particular, it could be useful in the treatment of wastewater, kinetic studies, drug delivery, the construction of novel supramolecular frameworks, metal-catalyzed reactions, recognition or response to metal cations, and so on.

Characterisation of chromites, chromite hosted inclusions of silicates and metal alloys in chromitites from the Indo-Myanmar ophiolite belt of Northeastern India

Chromite is commonly used to decipher the petrogenesis and geodynamic setting of ultramafic rocks. Podiform chromitites associated with the mantle sequence of the Indo-Myanmar ophiolite belt are studied here to characterise the major and trace element concentrations of the chromites. The molar ratios Cr# (100×Cr/(Cr+Al)) and Mg# (100×Mg/(Mg+Fe2+)) range from 67 to 82 and 66 to 71, respectively, in the chromites. Calculated equilibrium conditions for chromite crystallisation are 19–25kbar pressure, 1080–1240°C temperature and oxygen fugacity ranging between 0.30 and 0.58 log units above the FMQ buffer, showing that the samples formed in an upper mantle environment. Minor and trace element concentrations in the chromites (Ga 23–33ppm, Ni 1203–1843ppm, V 585–780ppm, Sc 2–5ppm) are comparable to other podiform chromitites hosted in the mantle sections of ophiolite complexes. Using chrome spinel compositions, the parental magma for the chromitite is identified as boninite. Tectonic discrimination diagrams using the primary composition of chromites indicate a supra-subduction zone setting for the Manipur ophiolite chromitites. The chromites host inclusions of silicates, base metal sulphides and base metal alloys. The diversity of these inclusions reflects the important role played by hydrothermal fluids. Inclusions (base metal sulphide and alloys) of linear trails with enriched Cr2O3 (63wt.%, Cr# ∼80) in the chromite grains (Cr2O3, Cr# 70) indicate mobility of this component in chromites.

Fabricating ternary hydrogels of P(AM-co-DMAEMA)/PVA/β-CD based on multiple physical crosslinkage

Ternary hydrogels composed of poly[acrylamide-co-2-(dimethylamino)ethyl methacrylate] [P(AM-co-DMAEMA)], poly(vinyl alcohol) (PVA) and β-cyclodextrin (β-CD) were fabricated based on the multiple physical interactions such as inclusion complexation, hydrogen bonding and polymer crystallinity, and exhibited high storage modulus. To illustrate the individual role of each physical interaction, symmetrical investigation has been performed. P(AM-co-DMAEMA)s with two compositions, prepared by radical polymerization at −20 °C below the freezing point of reaction medium of water, were served as the inclusion guest for the inclusion host of β-CD. The inclusion complex between dimethylaminoethyl group of DMAEMA and β-CD was identified through 2D NOESY NMR spectroscopy. Hydrogen bonding between each pairs of hydrogel components was confirmed with FTIR analysis and contributed the second form of crosslinkage. Under freezing polymerization and further freezing-thawing treatment, PVA component tended to crystallize to serve as the third type of physical crosslinkage, which was recognized with X-ray diffraction. Rheological and thermo-gravimetrical analysis was used to inspect the modulus and thermal stability of the hydrogels, respectively. Three hydrogels of P(AM-co-DMAEMA)/PVA-g-β-CD, P(AM-co-DMAEMA)/PVA/β-CD and P(AM-co-DMAEMA)/PVA were synthesized under the same condition to make the comparison. The whole results disclosed the strong dependence of hydrogel properties on the hydrogel components, reflecting the synergistic effects of different physical crosslinkages for the formation of those physical hydrogels.

Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach

Transmission Kikuchi diffraction (TKD) is a relatively new technique that is currently being developed for geological sample analysis. This technique utilises the transmission capabilities of a scanning electron microscope (SEM) to rapidly and accurately map the crystallographic and geochemical features of an electron transparent sample. TKD uses a similar methodology to traditional electron backscatter diffraction (EBSD), but is capable of achieving a much higher spatial resolution (5–10nm) (Trimby, 2012; Trimby et al., 2014). Here we apply TKD to refractory metal nuggets (RMNs) which are micrometre to sub-micrometre metal alloys composed of highly siderophile elements (HSEs) found in primitive carbonaceous chondrite meteorites. TKD allows us to analyse RMNs in situ, enabling the characterisation of nanometre-scale variations in chemistry and crystallography, whilst preserving their spatial and crystallographic context. This provides a complete representation of each RMN, permitting detailed interpretation of their formation history.We present TKD analysis of five transmission electron microscopy (TEM) lamellae containing RMNs coupled with EBSD and TEM analyses. These analyses revealed textures and relationships not previously observed in RMNs. These textures indicate some RMNs experienced annealing, forming twins. Some RMNs also acted as nucleation centres, and formed immiscible metal-silicate fluids. In fact, each RMN analysed in this study had different crystallographic textures. These RMNs also had heterogeneous compositions, even between RMNs contained within the same inclusion, host phase and even separated by only a few nanometres. Some RMNs are also affected by secondary processes at low temperature causing exsolution of molybdenite. However, most RMNs had crystallographic textures indicating that the RMN formed prior to their host inclusion. TKD analyses reveal most RMNs have been affected by processing in the protoplanetary disk. Despite this alteration, RMNs still preserve primary crystallographic textures and heterogeneous chemical signatures. This heterogeneity in crystallographic relationships, which mostly suggest that RMNs pre-date their host, is consistent with the idea that there is not a dominant RMN forming process. Each RMN has experienced a complex history, supporting the suggestion of Daly et al. (2017), that RMNs may preserve a diverse pre-solar chemical signature inherited from the Giant Molecular Cloud.

Adsorption of сucurbit[6]uril and styryl dye complexes on the surface of silver nanoparticles

Fluorescence spectroscopy and electrochemistry methods have been applied to study the adsorption of complexes of styryl dye, trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (DSMI), with cucurbit[6]uril (CB6) on the surface of silver nanoparticles (AgNPs) (with an average size of 15 nm) prepared by silver nitrate reduction using sodium borohydride. It is established that in the presence of AgNPs the intensity of fluorescence of the DSMI@CB6 complex decreases by approximately 40%; the fluorescence of only free complexes in the bulk solution is observed, and the fluorescence of the complexes, which were adsorbed on the AgNPs surface, is completely quenched. The Frumkin isotherm (adsorption equilibrium constant B = 7.0 × 106 L/mol) is used to describe the adsorption. In addition, the binding constant of the inclusion host–guest DSMI@CB6 complex is adjusted: K = 106 L/mol.

On the forbidden and the optimum crystallographic variant of rutile in garnet

In many inclusion–host systems with similar oxygen packing schemes, the optimum crystallographic orientation relationship (COR) between the inclusion and the host is mostly determined by matching the similar oxygen sublattices of the two structures. In contrast, the prediction of the optimum COR or even just the rationalization of the observed COR(s) between an inclusion and host with incompatible oxygen sublattices, like rutile–garnet, is not straightforward. The related documentation for such cases is therefore limited. Given the abundant crystallographic data for the rutile–garnet system acquired by transmission electron microscopy and electron backscatter diffraction methods recently, this problem can now be examined in detail for the critical structural factors dictating the selection of optimum COR in such a structurally complicated system. On the basis of the unconstrained three-dimensional lattice point match and structural polyhedron match calculated for the observed CORs, it becomes clear that the prerequisite of optimum COR for rutile (rt) in garnet (grt) is to have most of their octahedra similarly oriented/inclined in space by aligning 〈103〉rt and 〈111〉grt for needle extension growth. Further rotation along the 〈103〉rt//〈111〉grt direction then leads to the energetically most favorable COR-2 variant with a good lattice point match defined by the coincidence site lattice (CSL) and a good topotaxial match of the constituent polyhedra at the CSL points, leaving unfavorable COR-1′ in the forbidden zones. This understanding sheds light not only on hierarchical energetics for the selection of inclusion variants in a complicated inclusion–host system, but also on yet-to-be-explored [UVW]-specific CORs and hetero-tilt boundaries for composite materials in general.

The final stages of kimberlite petrogenesis: Petrography, mineral chemistry, melt inclusions and Sr-C-O isotope geochemistry of the Bultfontein kimberlite (Kimberley, South Africa)

The petrogenesis of kimberlites is commonly obscured by interaction with hydrothermal fluids, including deuteric (late-magmatic) and/or groundwater components. To provide new constraints on the modification of kimberlite rocks during fluid interaction and the fractionation of kimberlite magmas during crystallisation, we have undertaken a detailed petrographic and geochemical study of a hypabyssal sample (BK) from the Bultfontein kimberlite (Kimberley, South Africa).Sample BK consists of abundant macrocrysts (>1mm) and (micro-) phenocrysts of olivine and lesser phlogopite, smaller grains of apatite, serpentinised monticellite, spinel, perovskite, phlogopite and ilmenite in a matrix of calcite, serpentine and dolomite. As in kimberlites worldwide, BK olivine grains consist of cores with variable Mg/Fe ratios, overgrown by rims that host inclusions of groundmass phases (spinel, perovskite, phlogopite) and have constant Mg/Fe, but variable Ni, Mn and Ca concentrations. Primary multiphase inclusions in the outer rims of olivine and in Fe-Ti-rich (‘MUM’) spinel are dominated by dolomite, calcite and alkali carbonates with lesser silicate and oxide minerals. Secondary inclusions in olivine host an assemblage of Na-K carbonates and chlorides. The primary inclusions are interpreted as crystallised alkali-Si-bearing Ca-Mg-rich carbonate melts, whereas secondary inclusions host Na-K-rich C-O-H-Cl fluids.In situ Sr-isotope analyses of groundmass calcite and perovskite reveal similar 87Sr/86Sr ratios to perovskite in the Bultfontein and the other Kimberley kimberlites, i.e. magmatic values. The δ18O composition of the BK bulk carbonate fraction is above the mantle range, whereas the δ13C values are similar to those of mantle-derived magmas. The occurrence of different generations of serpentine and occasional groundmass calcite with high 87Sr/86Sr, and elevated bulk carbonate δ18O values indicate that the kimberlite was overprinted by hydrothermal fluids, which probably included a significant groundwater component. Before this alteration the groundmass included calcite, monticellite, apatite and minor dolomite, phlogopite, spinel, perovskite and ilmenite. Inclusions of groundmass minerals in olivine rims and phlogopite phenocrysts show that olivine and phlogopite also belong to the magmatic assemblage. We therefore suggest that the crystallised kimberlite was produced by an alkali-bearing, phosphorus-rich, silica-dolomitic melt. The alkali-Si-bearing Ca-Mg-rich carbonate compositions of primary melt inclusions in the outer rims of olivine and in spinel grains with evolved compositions (MUM spinel) support formation of these melts after fractionation of abundant olivine, and probably other phases (e.g., ilmenite and chromite). Finally, the similarity between secondary inclusions in kimberlite olivine of this and other worldwide kimberlites and secondary inclusions in minerals of carbonatitic, mafic and felsic magmatic rocks, suggests trapping of residual Na-K-rich C-O-H-Cl fluids after groundmass crystallisation. These residual fluids may have persisted in pore spaces within the largely crystalline BK groundmass and subsequently mixed with larger volumes of external fluids, which triggered serpentine formation and localised carbonate recrystallisation.

Crystallographic orientation relationships in host–inclusion systems: New insights from large EBSD data sets

Crystallographic orientation relationships (CORs) between mineral inclusions and their hosts could potentially deliver information about inclusion formation processes and conditions. Most previous studies are based on small numbers of analyses. This paper uses EBSD to study host–inclusion CORs in an inclusion-rich Permian metapegmatite garnet (Koralpe region, Eastern Alps, Austria), demonstrating the importance of large data sets and of EBSD in particular for the analysis of CORs. The distribution of measured orientations reflects host garnet point group symmetry for 89% of inclusions analyzed (total N = 530). Each inclusion phase (rutile, corundum, and ilmenite) shows at least three different CORs to host garnet. “Statistical” CORs are introduced to describe distributions of inclusion orientations that have one or two degrees of freedom with respect to the host, but still reflect host crystal symmetry. Two end-member characteristics of statistical CORs are distinguished: rotation and dispersion. Most statistical CORs observed show a mixture of both. Each inclusion phase shows at least one statistical COR. Multiple coexisting CORs and statistical CORs are not restricted to rutile. Re-examination of previous garnet–rutile COR studies in light of the new results indicates that COR information may have been overlooked when using small data sets. Variation in COR parameters correlates with broad differences in assumed metamorphic conditions for new and literature samples, suggesting that petrogenetic information may be available if COR formation can be understood. The favorability of the detected CORs cannot be explained by a simple model involving minimization of misfit between lattice planes, implying that other interface properties or the inclusion formation mechanism are important controls on COR development.

Methanol-Influenced Assembly of Metal–Organic Hybrid Compounds Based on Propane-1,3-diamine Ligands and [XCl4]2– (X = Zn, Hg)

The authors designed two flexible ligand molecules, namely, (N1,N1,N3,N3-tetrakis(4-methylbenzyl)propane-1,3-diamine) (L1) and (N1,N1,N3,N3-tetrabenzylpropane-1,3-diamine) (L2), with (CH2)3 alkyl chains attached to the two N atoms. The ligands are double protonated and can react with tetrachloride metal dianion [XCl4]2– (X = Zn, Hg) in the presence of methanol solvent, leading to a series of new inclusion complexes, (CH3OH)2 ⊂ [L1]2H+· [ZnCl4]2–(crystal 1), (CH3OH)0.5 ⊂ [L2]2H+·[HgCl4]2 (crystal 2), and CH3OH ⊂ {[L2]2H+}0.5· {[ZnCl4]2–}0.5 (crystal 3). The molar ratios of methanol and ligand are 2:1, 1:2, and 2:1 in the three crystals, respectively. The structures were characterized by NMR and single-crystal X-ray diffractions. The effect of guest methanol molecules on the formation of supramolecular assemblies was discussed. The ligand can adopt different molecular arrangements as so to suit for the demands of same guest species. From the structural view point, we showed the relationship between the diversity of inclusion hosts and conformational flexibility of ligand.

Synthesis and supramolecular interactions involved in the crystal structure of (2,4,10,12-tetrabromo-6,7,14,15-tetrahydro-6, 14-thiacycloocta[1,2-b:5,6-b’]diquinoline)2·(1,1,2,2-tetrachloroethane) inclusion compound

The tetrahalo aryl inclusion host 2,4,10,12-tetrabromo-6,7,14,15-tetrahydro-6,14-thiacycloocta[1,2-b:5,6-b’]diquinoline 3 was re-synthesized to explore its ability to trap toxic polychlorinated hydrocarbons such as 1,1,2,2-tetrachloroethane (TCE) in the form of host–guest compound. Host 3 crystallizes from a fresh sample of TCE to form an inclusion compound of the formula (3)2·(TCE) in triclinic system, space group P-1, with a = 7.7732(16) Å, b = 10.739(2) Å, c = 14.816(3) Å, α = 97.329(4)°, β = 98.619(4)°, γ = 103.359(4)°, V = 1172.7(4) Å3, and Z = 2. The X-ray crystal structure of the (3)2·(1,1,2,2-TCE) is described and analyzed in terms of crystal engineering and supramolecular chemistry. The hosts assemble by means of different types of packing motifs. The included TCE molecules are enclosed within host molecular pens. Novel halogen···halogen intermolecular interactions as well as other non-covalent intermolecular interactions involved in the crystal structure are presented and proved to play an important role in linking these host–host, host–guest, and guest–guest building blocks.

Structure and stoichiometry of resorcinarene solvates as host–guest complexes – NMR, X-ray and thermoanalytical studies

Controlled release of a guest from inclusion host–guest complexes is an important aspect of design and synthesis of advanced materials for sensing, purification, chromatography, and storage of wide variety of molecules. In this work, host–guest complexes of C-methylcalix[4]resorcinarene (RES1) and C-undecylcalix[4]resorcinarene (RES2) with four solvents were examined by NMR, X-ray and thermoanalytical techniques in order to compare their stoichiometries, solvent effects, the role of water during solubilization/complexation process. The phenomena of poor solubility of some resorcinarenes in dry solvents versus their good solubility in wet solvents is explained on example of resorcinarene/dioxane/water complex. An asymmetric unit contains RES1 macrocycle in C2v symmetry which adopts a boat-like conformation and RES1 is a rccc isomer with four axial methyl groups. Water is a molecular linker that organizes the whole network in RES1·2dioxane·3H2O solvate.

How large are departures from lithostatic pressure? Constraints from host–inclusion elasticity

AbstractMinerals trapped as inclusions within other host minerals will develop non‐lithostatic pressures during both prograde and retrograde metamorphism because of the differences between the thermoelastic properties of the host and inclusion phases. There is only a single possible path in P–T space, the entrapment isomeke, along which no residual pressure would be developed in a host–inclusion system; non‐lithostatic pressures are developed in inclusions as a result of the external pressure and temperature deviating from the isomeke that passes through the entrapment conditions. With modern equation of state and elasticity data for minerals now available, it is possible to perform precise calculations of the isomekes for mineral pairs. These show that isomeke lines are not straight lines in P–T space at metamorphic conditions. We show that silicate inclusions in silicate hosts tend to have flat isomekes, with small values of , because of the small range of thermal expansion coefficients of silicate minerals. As a consequence, the general behaviour under decompression is for soft silicate inclusions in stiffer hosts to develop excess pressures, whereas a stiff silicate inclusion in a softer matrix will experience lower pressures than lithostatic pressure. The opposite effects occur for compression after entrapment on the prograde path. The excess pressures in inclusions, including allowance for mutual elastic relaxation of the host and inclusion, are most easily calculated by using the isomeke as a basis. Analysis of the simplest possible model of a host–inclusion system indicates that deviations from lithostatic pressure in excess of 1 GPa can be readily produced in quartz inclusions within garnet in metamorphic rocks. For softer host minerals such as feldspar, the pressure deviations are smaller, because of greater elastic relaxation of the host. The maximum pressure deviation from lithostatic pressure in the host phase around the inclusion is one‐third of the pressure deviation in the inclusion. Routines for performing these calculations have been added to the EosFit7c software package.

Internal diamond morphology: Raman imaging of metamorphic diamonds

Confocal 2‐D and 3‐D Raman imaging of the Kokchetav metamorphic diamonds from different rock types reveals that these diamonds have a rather complex internal morphology. The diamond shows a strong change in the position of the diamond Raman line as well as the width of this line, which could be found both in the XY and in the YZ scan. These features indicate variations in the crystalline quality of the diamond. The broadest lines are located in the center of the octahedral diamond inclusion whereas the material close to the diamond–garnet interface shows smaller line widths. These features were also found for thermochemically extracted diamond crystals, which are not armored by host mineral, and in situ for inter‐ and intragranular diamond. Furthermore, host–garnet display no evidence for broadening or up‐shift of main Raman bands, indicating very low (below detection limit) residual strain. Thus the broadening and upshift of main diamond band do not relate to residual strain in inclusion–host systems. A comparison of Raman imaging results with cathodoluminescence images reveals that the distribution of defects, which cause the cathodoluminescence of diamond crystals, can be traced by Raman imaging. The 2‐D and 3‐D Raman imaging is a very powerful tool for study of internal morphology and growth pattern of metamorphic diamond, even it is a small crystal less than 10 µm in size. The growth pattern for octahedral diamond crystals from garnet–clinozoisite gneisses were obtained for the first time by Raman imaging. Copyright © 2015 John Wiley & Sons, Ltd.

Encapsulation of Halocarbons in a Tetrahedral Anion Cage

AbstractCaged supramolecular systems are promising hosts for guest inclusion, separation, and stabilization. Well‐studied examples are mainly metal‐coordination‐based or covalent architectures. An anion‐coordination‐based cage that is capable of encapsulating halocarbon guests is reported for the first time. This A4L4‐type (A=anion) tetrahedral cage, [(PO4)4L4]12−, assembled from a C3‐symmetric tris(bisurea) ligand (L) and phosphate ion (PO43−), readily accommodates a series of quasi‐tetrahedral halocarbons, such as the Freon components CFCl3, CF2Cl2, CHFCl2, and C(CH3)F3, and chlorocarbons CH2Cl2, CHCl3, CCl4, C(CH3)Cl3, C(CH3)2Cl2, and C(CH3)3Cl. The guest encapsulation in the solid state is confirmed by crystal structures, while the host–guest interactions in solution were demonstrated by NMR techniques.

Encapsulation of Halocarbons in a Tetrahedral Anion Cage.

Caged supramolecular systems are promising hosts for guest inclusion, separation, and stabilization. Well-studied examples are mainly metal-coordination-based or covalent architectures. An anion-coordination-based cage that is capable of encapsulating halocarbon guests is reported for the first time. This A4L4-type (A=anion) tetrahedral cage, [(PO4)4L4](12-), assembled from a C3-symmetric tris(bisurea) ligand (L) and phosphate ion (PO4(3-)), readily accommodates a series of quasi-tetrahedral halocarbons, such as the Freon components CFCl3, CF2Cl2, CHFCl2, and C(CH3)F3, and chlorocarbons CH2Cl2, CHCl3, CCl4, C(CH3)Cl3, C(CH3)2Cl2, and C(CH3)3Cl. The guest encapsulation in the solid state is confirmed by crystal structures, while the host-guest interactions in solution were demonstrated by NMR techniques.

Synthesis of refractory metal nuggets and constraints on the thermal histories of nugget‐bearing Ca, Al‐rich inclusions

AbstractTiny refractory metal nuggets are mainly observed inside Ca, Al‐rich inclusions (CAIs) from chondritic meteorites and are commonly assumed to be condensates from a solar composition gas. However, recent detailed studies of metal nugget compositions and their comparison with predictions from condensation show that the observed abundance patterns are extremely difficult to achieve in this way. As a test for the proposed alternative, precipitation from a silicate liquid, we conducted melting experiments, in which nine different refractory metals (nugget components) were equilibrated with each other along with a CAI‐like liquid at reducing conditions. When quenched, minerals similar to those in CAIs formed from such liquids including refractory metal nuggets exhibiting compositions and appearances similar to those of the meteoritic nuggets. The run products and their comparison with a meteoritic nugget‐bearing CAI is evidence for formation of refractory metal nuggets during cooling of Ca, Al‐rich liquids at rates about 1000°/40 s (in the interval from 1900 to 900 °C). To achieve the formation of refractory metal nuggets and the textures observed in the host inclusions, during cooling the rate probably changed. Refractory metal nuggets apparently formed during quenching before spinel crystallized.

Tetraarylbiphenyl as a New Lattice Inclusion Host by Structure Reductionism: Shape and Size Complementarity Based on Torsional Flexibility

3,3′,5,5′-Tetrakis(2,6-dimethyl-4-methoxyphenyl)biphenyl (TB) was designed as a lattice inclusion host based on a structure reductionistic approach. TB binds guests in two different domains based on the premise that the two phenyl rings of the biphenyl core remain coplanar in the solid state. The versatility of TB as a host has been demonstrated by its ability to include different guest molecules in the crystal lattice, as revealed by X-ray crystal structure analyses. One observes preference for guest location in the concave domain with the trough domain compromised. The host TB is found to exploit torsional freedom about the central σ-bond between the two phenyl rings of the biphenyl core to adopt discrete structures that are complementary in terms of shape and size to include a given guest. In other words, TB behaves like a “molecular chameleon” that undergoes structural adaptation in response to the guest via torsional twist about the central σ-bond. Quite remarkably, the inclusion compounds with different guests having similar torsional angles between the phenyl rings of the biphenyl core are found to be isostructural. The torsion-induced structural morphosis in response to the guest is found to completely offset binding in the trough region.