From crown ethers to zeolites: Reaction of EtAlCl2 with crown ethers

In contrast to aluminum alkyls, alkyl aluminum halides such as EtAlCl₂ react with crown ethers to form cation-anion pairs which exhibit the liquid clathrate effect. Specifically, [12-C-4·AlCl₂][AlCl₃Et] and [18-C-6·AlCl₂][AlCl₃Et] have been isolated and characterized by X-ray diffraction techniques. The cations show aluminum in an octahedral environment made up of four of the oxygen atoms from the crown and two chlorine atoms. The 12-C-4 derivative crystallizes in the monoclinic space group P2₁/c with cell constants of a=7.497(4), b=22.121(8), c=12.339(5) Å, =94.99(3)^o, and Z=4 for =1.43 g cm^–3. Least-squares refinement based on 1413 observed reflections led to a final conventional R value of 0.093. The 18-C-6 complex belongs to the triclinic space group P1 with a=8.414(4), b=12.193(6), c=12.394(6) Å, =73.14(4), =86.07(4), =81.52(4)^o, and Z=2 for =1.45 g cm^–3. Refinement based on 2605 observed reflections led to R=0.063. The complex aluminum-containing species are related to a class of compounds called aluminoxanes.     

冠醚的分子设计及其识别性质研究进展

综述了冠醚化学研究的最新进展：包括低对称冠醚、臂式冠醚、双冠醚等的分 子设计和离子键合、离子识别的热力学起源和分子组装的研究进展。     

Template-induced and molecular recognition directed hierarchical generation of supramolecular assemblies from molecular strands

The linear oligo-isophthalamide strand 1 undergoes a conformational reorganization upon binding of a cyanuric acid template as effector to afford a helical disklike object possessing radially disposed alkyl residues. Solvophobic and stacking interactions, in turn, drive a "second level" self-assembly of the templated structure, the stacking of the helical disks, to yield fibers as revealed by electron microscopy. These data provide insight into the interplay of the different structural and interactional features of the molecular components towards the formation of supramolecular fibers through sequential hierarchical self-assembly events and suggest design strategies for the effector-controlled generation of related supramolecular assemblies.     

Oxidation of organic sulfur compounds with hydrogen peroxide in the presence of crown ethers

Hydrogen peroxide oxidizes methyl phenyl sulfide and benzothiophene in the presence of crown ethers to the corresponding sulfoxides and sulfones. The oxidation is retarded by amino acids. UV and NMR spectroscopies show that, at the initial stage of oxidation, complexation occurs between crown ether, hydrogen peroxide, and sulfide, as well as between crown ether and amino acid.     

A molecular mechanics study of neutral molecule complexation with crown ethers

Molecular mechanics methods are applied to the study of neutral molecule complexation with crown ethers. Protocols for the development of parameters necessary to describe these molecule-molecule interactions are presented. Application of these methods to the study of 1:1 and 2:1 (guest:host) complexation between acetonitrile (1), nitromethane (2), malononitrile (3) and dimethylsulfone (4) reveals positive cooperativity in formation of the 2:1 complexes in isolation.     

From novel complexing conditions to novel coordination compounds of nickel(II) with dithiooxamide and its bulky analogues

Summary Novel complexing processes in the Ni^II-dithiooxamide, Ni^II-N,N-diphenyldithiooxamide and Ni^II-quinoxaline-2,3-dithiol systems, which have not been used in coordination chemistry before, namely complexing in a nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the corresponding ligand, have been studied. Under these specific conditions, in the Ni^II-dithiooxamide system, five different coordination compounds are formed, four of which are insoluble in H₂O. In the Ni^II-quinoxaline-2,3-dithiol system, three different complexes formed (each of them insoluble in H₂O) and, in the Ni^II-diphenyldithiooxamide system, only one insoluble complex is formed. Whereas, complexing in solution or the solid phase, formation of only one complex is observed in each of systems cited     

From novel complexing conditions to novel coordination compounds of copper(II) with dithiooxamide and its bulky analogues

Novel complexing processes in the CuII–dithiooxamide, CuIIN, N-diphenyldithiooxamide and CuII–quinoxaline-2,3-dithiol systems, which have been used in coordination chemistry before, namely complexing into a copper(II) hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the corresponding ligand, have been observed and analysed. Under these specific conditions, in each of the CuII–dithiooxamide and CuII–quinoxaline-2,3-dithiol systems, three different coordination compounds are formed, two of which are insoluble in water; in the CuII–diphenyldithiooxamide system, only one water-insoluble complex is formed. Conversely, complexing in solution or solid phase results in the formation of only one complex in each of the systems cited above. This revised version was published online in June 2006 with corrections to the Cover Date.     

Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC

Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na⁺] and not on [K⁺] at concentrations of K⁺ from 5×10^–7 to 10^–1 mol l^–1. Hence, actinomycin D may be classified as an ionophore-antibiotic.     

Synthesis of novel crown ethers. Part 1. Coumestan and coumestan analog derivatives of crown ethers

The presented ethylenedioxy compounds5a,5d,6a and6c are examples of novel cyclic ethers, while macrocyclic polyethers represent new crown ether analogues. New coumestan-crowns5a-f, derivatives of 6,7-dihydroxy-3,4-dihydro-2H-dibenzofuran-1-one and 6,7-dihydroxy-3,3-dimethyl-3,4-dihydro-2H-dibenzofuran-1-one6a-e were synthesized from the correspondingo-dihydroxy compounds3a-b,4a-b and ditosylates or dichlorides of di- or triethylene glycol in the presence of K₂CO₃, in DMF/H₂O (15/1) solutions at 65–75 °C for 35 hours. The structure of the macrocyclic ethers obtained were confirmed by¹H-NMR,¹³C-NMR, IR spectra and elemental analyses.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Coamplexation of mercury(II) compounds by crown ethers in organic media

Complexes between crown ethers having ring sizes of 15–24 atoms and 5 to 8 oxygens with HgX₂ species (X = Cl, I, CN, SCN) have been prepared and studied. Interactions of the substituents X bound to mercury with groups or fragments in the crown compound are essential in determining the characteristics and stability of the complexes formed. Complexes with crowns of 18C6 ring sizes are the most favourable except for HgX₂ compounds for which the size of X is larger than the macrocycle ring, as is the case for X = CF₃.     

Inclusion compounds: The products of the interaction of silicon,germanium and boron fluorides with crown ethers

This review deals with the problem of the interaction of Si(IV), Ge(IV) and B(III) fluorides with crown ethers and their aza analogues. The crystallographic structures have been determined of the stable products obtained by the interaction of H₂SiF₆ solution with the following crown ethers: 18-crown-6 (18C6), monoaza-18C6 (MA18C6), 1,10-diaza-18C6 (DA18C6) and 1,7-diaza-15C5 (DA 15C5). The complexes obtained are stabilized by a system of H-bonds of the O-H... O, N-H. ... O, N-H...F and O-H ... F types. For H₂GeF₆ the adducts obtained are similar to those obtained using H₂SiF₆. The crystal structures of three new boron fluoride-containing complexes with 18-membered crown ethers are also described. During macrocycle complexation the guest entities undergo chemical transformations which are stabilized by creation of the H- bond system. The results of vibrational and NMR spectra are also discussed.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

生色冠醚研究 I: 双偶氮开链冠醚的合成和与金属离子的配位性能

本文用邻苯二酚经过先桥接后偶联,用愈创木酚,水杨醛经过先偶联后桥接的方法,合成了三类双偶氮开链冠醚1,2和3.方法简便,产率较高,借助于可见光谱测定,考查了它们在溶液中与碱金属和碱士金属盐等的配位性能.结果表明,1在95:5四氢呋喃-水(v/v)中,对高氯酸锂和高氯酸钙有良好的选择性变色作用.本文对变色作用的反应机理进行了详细的讨论.可以认为,变色作用的产物是分子内配盐,这已由1与高氯酸钙制成的配合物的元素分析,可见光谱和红外光谱的测定所证明.     

Lanthanide complexes with oda, ida, and nta: From discrete coordination compounds to supramolecular assemblies

Lanthanide metal–organic frameworks have been receiving special attention for the last decade. The use of polydentate organic ligands has allowed the construction of interesting network topologies with many potential applications, based on the special characteristics of the 4f electrons. In this paper, the structural and thermodynamic properties of Ln(III) complexes with oxydiacetate, iminodiacetate, and nitrilotriacetate are critically reviewed. The presence of ligands able to act as a bridge promotes the formation of Ln–M polynuclear complexes with fascinating 3D structures, whose study is also included. Equilibrium data of these systems in aqueous solution have been collected, showing the relationship between the composition of the species in solution and the nuclearity in the solid state.     

Luminescence of lanthanides in complexes with chromophoric crown ethers

Spectral luminescence characteristics, viz., quantum yields and luminescence lifetime, of the Yb³⁺ and Nd³⁺ ions in aqueous-methanolic solutions of their complexes with chromophoric benzo-15-crown-5 derivatives were determined. The efficient 4f-luminescence (_exc = 337 nm) is due to the intramolecular transfer of the excitation energy from the chromophoric moiety of the molecule to the Ln³⁺ ion.     

Application of the okahara cyclization to the preparation of crown ethers with aromatic units

A series of crown ethers with single benzene, naphthalene, biphenyl and binaphthyl units are prepared by the intramolecular Okahara cyclization of appropriate symmetrical diols. The method is used to synthesize new crown ether compounds and to prepare previously-reported crown ethers in improved yields.