Cyclophanes as hosts for aromatic and aliphatic guests

A series of water-soluble cyclophanes, made by connecting two diarylmethane units and two bridging chains via four nitrogens, were found to provide hydrophobic cavities of definite shape and size for forming inclusion complexes with various organic compounds in aqueous solution. Some chemical modifications of these cyclophanes are described.This paper is dedicated to Professor D. J. Cram to celebrate his honor in receiving the 1987 Nobel Prize in Chemistry.     

New crystal structures of β-[Ni(NCS)2(4-methylpyridine)4] clathrates with furan,tetrahydrofuran, methylene chloride,benzene + ethanol and methylcellosolve as guest molecules

Single crystal X-ray structures of clathrates of -[Ni(NCS)₂(4-methylpyridine)₄] with furan, tetrahydrofuran, benzene + ethanol, methylene chloride, and methylcellosolve as guests molecules are reported. The location of the guest molecule in the partially decomposed clathrate with methylene chloride was defined by X-ray diffraction and compared with the fully occupied one. The host lattices of all clathrates studied are tetragonal (I4₁/a) and do not differ significantly from typical -phase clathrates of [M(NCS)₂(4-methylpyridine)₄] (M = divalent metal cation). Arrangements of guest molecules represent different types of packing: one type of guest molecule occupies both possible types of positions, two different guest molecules occupy different positions, with only one type of positions occupied by one type of guest molecule. Possible stoichiometries of clathrates with -type lattices are discussed.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August 1995.     

Preparation,Characterization and Optical Properties of Hostguest Nanocomposite Material Mordenite—silver Iodide

Silver iodide nanoclusters were successfully prepared in the channels of mordenite by a heat diffusion method.Powder X-ray diffraction.adsorption technique and infrared spectroscopy were used to characterize the prepared materials,which showed that the guest silver iodied had been encapsulated in the channels of mordenite.The optical properties of the solid phase diffuse reflectance absorption of nanocomposite material NaM-AgI were studied,showing that the absorption bands of the diffuse reflectance absorption of the prepared material moved to the region of high energy.The absorption peak of the material prepared shifted to the region of high energy.Namely,blue shift was caused.This has demonstrated the incorporation of silver iodide into the channels of the zeolite.We observed the luminescence and surface photovoltage spectra of NaM-AgI sample,proposing the mechanisms of the photoluminescence and photovoltaic responses.     

Supramolecular drug inclusion complex constructed from cucurbit[7]uril and the hepatitis B drug Adefovir

The interaction between cucuribit[7]uril (Q[7]) and Adefovir (ADV) has been studied in aqueous solution by ¹H NMR spectroscopy, electronic absorption spectroscopy, Isothermal Titration Calorimetry and mass spectrometry. The results revealed that an inclusion complex was formed via encapsulation of the purine rings of the guest ADV, while the phosphonomethoxyethyl group was prevented from entering the cavity. ITC data revealed that the formation of this 1:1 inclusion complex is mainly driven by favourable enthalpy changes. Studies investigating the release of ADV from the inclusion complex revealed enhanced rates under acidic conditions, although the rates were slower than observed for the free guest under the same conditions. Thermal stability studies indicated that the included form of ADV was more stable that the free form.     

Simulations of Guest Transport in Clathrates of Dianin’s Compound and Hydroquinone

Clathrates have been proposed for use in a variety of applications including gas storage, mixture separation and catalysis due to the potential for controlled guest diffusion through their porous lattices. Here molecular dynamics simulations are employed to study guest transport in clathrates of hydroquinone (HQ) and Dianin’s compound (DC). Systems investigated were HQ with methanol and acetonitrile, and DC with methanol and ethanol. Simulations were set up with one guest in the pore, two guests in the pore and one vacancy in the pore and a filled pore, and free‐energy barriers for movement between cavities of the pore were estimated for all cases. Comparison between these simulations indicates that guest transport most likely proceeds by molecules moving from full to empty cavities consecutively, one by one, rather than in a concerted manner. Thus, the presence of empty cavities is very important for guest transport, which becomes more energetically demanding in fully loaded systems. Flexibility of the host can assist guest transport. In the studied DC clathrates transport occurs via an intermediate conformation in which the hydroxyl group of the alcohol guest molecule participates in the hydrogen‐bonded ring of the host. We also address the issue of the number of methanol guest molecules that DC accommodates, for which conflicting information exists. We found that this is likely to be temperature dependent and suggest that under some conditions the system is most likely non‐stoichiometric.     

AN OCTAPHENYL-SUBSTITUTED BICYCLIC ORGANOMETALLIC INCLUSION HOST

Abstract

As part of a study involving design of new organometallic hosts, Pd₂(dpm)₂Cl₂ 5 was reacted with 4-isocyanoacetophenone 6 to produce the organometallic insertion product 7. This forms an unstable ternary inclusion compound (7)·(chloroform)·(dimethyl sulfoxide) whose X-ray crystal structure [C₅₉H₅₁Cl₂NOP₄Pd₂·CHCl₃·C₂H₆OS, P2₁2₁2₁, a = 14.734(2), b = 15.782(2), c = 26.682(4) Å, Z = 4, R = 0.043] was determined. The host phenyl groups intermesh producing a helical arrangement of molecules of 7 generated by a 2₁ screw axis. Chloroform guests form a second helix intertwining that of the organometallic host through involvement in C = O…H-CCl₃ hydrogen bonds. The dimethyl sulfoxide guests exhibit no significant short intermolecular contacts.     

客体小分子在超分子有机凝胶体系中的扩散释放

采用二(4-硬脂酰胺基苯基)甲烷(BSAPM)为凝胶剂制备了含有小分子水杨酸和若丹明B的1,1,2-三氯乙烷(TCE)超分子有机凝胶. 以超分子有机凝胶作为主体, 客体小分子水杨酸和若丹明B可轻微降低超分子有机凝胶的相转变温度(T_GS). 用紫外-可见光度法研究了超分子凝胶中两种客体小分子在静态下的扩散释放. 结果表明其释放率随凝胶剂浓度的增加而降低. 客体小分子的体积大小对其释放有明显的影响, 分子体积较大的若丹明B的释放率低于分子体积较小的水杨酸. 另外, 若丹明B的扩散系数也低于水杨酸, 且随凝胶剂浓度的增加, 这种趋势更为明显. 两种客体分子的累积释放率与时间的平方根成良好的线性关系, 符合Higuchi方程, 属扩散控制的Fickian释放机理.     

A Tunable Cyclic Container: Guest‐Induced Conformational Switching,Efficient Guest Exchange,and Selective Isolation of C70 from a Fullerene Mixture

An adaptable cyclic porphyrin dimer with highly flexible linkers has been used as an artificial molecular container that can efficiently encapsulate various aromatic guests (TCNQ/C₆₀/C₇₀) through strong π–π interactions by adjusting its cavity size and conformation. The planar aromatic guest (TCNQ) can be easily and selectively exchanged with larger aromatic guests (C₆₀/C₇₀). During the guest‐exchange process, the two porphyrin rings switch their relative orientation according to the size and shape of the guests. This behavior of the cyclic container has been thoroughly investigated by using UV/Vis spectroscopy, NMR spectroscopy, and X‐ray crystal structure determination of the host–guest assemblies. The electrochemical and photophysical studies demonstrated the occurrence of photoinduced electron transfer from bisporphyrin to TCNQ/C₆₀/C₇₀ in the respective host–guest assemblies. The cyclic host can form complexes with C₆₀ and C₇₀ with association constants of (2.8±0.2)×10⁵ and (1.9±0.3)×10⁸ m ⁻¹, respectively; the latter value represents the highest binding affinity for C₇₀ reported so far for zinc(II) bisporphyrinic receptors. This high selectivity for the binding of C₇₀ versus C₆₀ allows the easy extraction and efficient isolation of C₇₀ from a C₆₀/C₇₀ fullerene mixture. Experimental evidence was substantiated by DFT calculations.     

The stabilization of thermodynamically disfavoured conformers of chlorocyclohexane in the host lattice of tri-ortho-thymotide. Crystallographic and infrared spectroscopic studies

The clathrate compounds of tri-o-thymotide have been prepared with chlorocyclohexane, bromocyclohexane and 2-chlorotetrahydropyran. The cage-type inclusion complex C₃₃H₃₆O₆ · ₂ ¹ C₆H₁₁Cl (trigonal,P3₁21,a=13.604(1),c=30.605(1) Å,Z=6) contains an axial-Cl chair and an axial-Cl boat conformation of the guest, distributed statistically in the ratio 2 1 over the available sites. The observed conformations have been compared with conformers calculated by force field methods. IR spectra are consistent with the crystal structure results for the tri-o-thymotide/chlorocyclohexane clathrate. They further demonstrate the similar preferential inclusion of axial isomers of bromocyclohexane and 2-chlorotetrahydropyran. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82023 (16 pages).Dedicated to Professor H. M. Powell.     

Anisotropic Expansion of an M2L4 Coordination Capsule: Host Capability and Frame Rearrangement

Anisotropic expansion of a spherical M₂L₄ coordination capsule through the elongation of the ligand led to a new M₂L′₄ capsule. The expanded capsule provides an elliptical cavity encircled by polyaromatic frameworks with large openings and thereby can encapsulate elliptical fullerene C₇₀ and monofunctionalized fullerene C₆₀ in high yields. In addition, selective formation of a new M₂L₂L′₂ capsule occurs by mixing the original M₂L₄ and expanded M₂L′₄ capsules in a 1:1 ratio upon addition of C₆₀ or monofunctionalized C₆₀ as a template molecule.     

Controlled Growth of Hybrid Halide Perovskites by Crown Ether Complexation for Perovskite Solar Cells

Host-guest complexation has demonstrated potential for controlling hybrid organic-inorganic metal halide perovskite materials. In particular, crown ethers have been used due to their capacity to interact with metal cations (e. g., Pb²⁺) and small organic cations (e. g., methylammonium (MA)), which can affect hybrid perovskite materials and their solar cells. However, this strategy has been underexploited in perovskite photovoltaics, and the underlying mechanisms are not well understood. In this study, we investigate the influence of 15-crown-5 ( 15C5 ) and its benzannulated derivative (benzo-15-crown-5, B15C5 ), as well as amino-functionalized analogues (15-crown-5)-2-methylamine, 2A-15C5 , and 4′-aminobenzo-15-crown-5, 4A-B15C5 , on MAPbI₃ perovskite crystallization and inverted solar cell performance. We demonstrate the propensity of crown ether modulators to interact with Pb²⁺ cations at the perovskite interface by density functional theory calculations. This has been shown to facilitate oriented crystal growth and homogeneous film formation, as revealed by X-ray diffraction analysis complemented by scanning electron microscopy. As a result, we demonstrate an increase in the power conversion efficiency of the solar cells of interest to advancing hybrid photovoltaics.     

Substitution effects on the binding interactions of redox-active arylazothioformamide ligands and copper(I) salts

ABSTRACT

The straightforward synthesis of redox-active arylazothioformamide (ATF) ligands allows for electronic diversity as to measure the weak-binding interactions of transition metal salts in supramolecular coordination complexes. A small library of para-substituted ATFs was created with varied electronic components to evaluate how electron-donating and electron-withdrawing groups alter binding association constants. Following full characterisation, including single-crystal X-ray diffraction, UV-Vis titration studies were performed using copper(I) salts to assess the Host:Guest binding. Simultaneously, substitutions were evaluated computationally by modelling the Gibbs’ Free Energy change of the rotational barriers from ligand crystal structures to the predicted metal coordinating species and the various complexes. The multi-model association calculations and experimental measurements interplay to help limit error propagations and reliably predict the more accurate binding models. Through a thorough investigation it was found that experimentally, each ligand supports a 2:1 binding model yet may employ unique binding mechanisms to achieve that model.     

卟啉-Salen化合物对含氮杂环客体的分子识别

A novel porphyrin-salen compound and corresponding zinc(Ⅱ)porphyrin-salen compound(ZnPSC_(10))cova-lently linked by a flexible alkoxy chain(—O(CH)_(10)O—)have been synthesized and characterized.Molecular rec-ognition of three N-heterocyclic guests,pyridine,1,4-diazobycyclo[2,2,2]octane(DABCO)and pyrazine,with thehost ZnPSC_(10)was investigated.Binding constants were determined by means of UV-vis titration method.Thebinding mode of ZnPSC_(10)with DABCO has been discussed in detail by using ~1H NMR.It was found that the con-formations of the recognition system changed from closed to open with the adding of DABCO.     

Synthesis and supramolecular properties of glycoluril tetramer

Synthesis of glycoluril tetramer bearing hydrogen atoms on its convex face and framed by two xylylene units is reported. This tetramer forms dimeric aggregates in the solid state. Host–guest properties of the tetramer with various ammonium and pyridinium guests were determined using ¹H NMR spectroscopy. The results were compared with structurally related host molecules.     

Transport of Guest Molecules by Unimolecular Micelles Evidenced in Analytical Ultracentrifugation Experiments

The ability of star‐shaped, block copolymer‐based unimolecular micelles to encapsulate and transport guest molecules was studied. Analytical ultracentrifugation studies clearly showed that methyl‐orange guest molecules could be encapsulated and transported, together with unimolecular micelles consisting of 5‐arm, star‐shaped block copolymers with a poly(ethylene glycol) core and a poly(ε‐caprolactone) corona. Sedimentation‐velocity and equilibrium measurements were performed to determine the sedimentation coefficients, molar masses, and diffusion coefficients of the loaded, unimolecular micelles. It was observed that the transport of guest molecules by unimolecular micelles was a function of the molecular weight of the star‐shaped block copolymers and therefore also of their size.

     

Solvent effect on the complex formation of distally dialkylated calix[4]arenes with 1-chloro-4-(trifluoromethyl)benzene

The complexation behavior of the distally dialkylated calix[4]arenes and 4-tert-butylcalix[4]arenes (hosts) with 1-chloro-4-(trifluoromethyl)benzene (guest) was examined in four different alcohols (MeOH, EtOH, n-PrOH, n-BuOH) as solvents. The complex stability constants (K_s) and the complexation energy of the host-guest complexes were determined. Fair ‘by group’ linear correlations between each log K series determined in the same solvent and the complex stabilization energies were found. As a consequence, the solvents having high permittivities result in less stability of the host-guest complex in these particular cases examined.