Efficient syntheses and crystal structures of new benzene-containing cryptands

Seven new cryptands 3–9 containing two or three aromatic rings in one bridge were prepared in good yields by treating N,N'-bis(p-chlorophenol)-substituted diaza-18-crown-6 ( 2 ) with three oligoethylene glycol ditosylates, 1,3-propanediol ditosylate, 2,6-pyridinedimethanol ditosylate, α,α'-dibromo-o-xylene and α,α'-dibromo-p-xylene. Because of the convenient synthesis of 2 from N,N'-bis(methoxymethyl)diaza-18-crown-6 ( 1 ) and the relative ease of isolation of the cryptand products, this is an excellent method for the design of three-dimensional cavities containing aromatic fragments. In an attempt to better understand the synthetic route to the cryptands, the crystal structures of KI·2 and Na Picrate·2 were determined using X-ray analysis. In addition, crystal structure analyses of cryptands 3, 6 and 8 were used to establish their structures.     

Two [2]pseudorotaxane-like complexes and their corresponding [2]rotaxanes stabilized via interactions on opposite ends of the same macrocycle

A multiple-use macrocycle recognizes dibenzylammonium ions and 2,6-lutidine derivatives, each in a [2]pseudorotaxane-like manner, through interactions with its diethylene glycol (hydrogen bonding) and 2,6-pyridinedicarboxamide (Pd²⁺ chelation) spacers, respectively. We characterized these complexes in the solid state (X-ray crystallography) and in solution (¹H NMR spectroscopy). The synthesis of two corresponding [2]rotaxanes confirmed that these recognition systems possess [2]pseudorotaxane geometries in solution.     

Supramolecular amphiphilies based on water-soluble pillar[5]arene/paraquat derivatives and their self-assembly behaviour in water

Supramolecular amphiphilies based on water-soluble pillar[5]arene/paraquat derivatives were successfully prepared. We found that when the length of the alkyl chain on guest molecules shorter than C₁₂, it formed micelles, on the other hand, when the alkyl chain longer than C₁₂, vesicles were obtained. Furthermore, we have demonstrated that the resulting vesicles can respond to multiple external stimuli, including temperature, host–guest inclusion and pH. Methods of warming, decreasing the pH of the system and inclusion of α-cyclodextrins were then employed to disrupt the vesicle architecture. Finally, controlled release experiments were performed to evaluate the vesicles which could encapsulate calcein within their interiors under neutral conditions and release it in response to a decrease in pH.     

Molecular catenation via metal-directed self-assembly and pi-donor/pi-acceptor interactions: efficient one-pot synthesis, characterization, and crystal structures of [3]catenanes based on Pd or Pt dinuclear metallocycles

Dinuclear square metallocycles 3a,b assemble spontaneously when M(en)(OTf)2 (M = Pd, Pt) and a 4,4'-bipyridinium ligand are mixed in acetonitrile. Six new [3]catenanes were prepared in good yields by thermodynamically driven self-assembly reaction of molecular squares 3a,b and pi-complementary dioxoaryl cyclophanes. Single-crystal X-ray analyses of the [3]catenanes revealed the insertion of two aromatic units inside the metallocycle cavity. The structures are stabilized by means of a combination of pi-pi stacking, [C-H...pi] interactions, and [C-H...O] hydrogen bonds. [3]Catenane (DB24C8)2-(3a) showed in solid-state two external DB24C8 rings positioned over the Pd(en) corners, which are held in position by [N-H...O] hydrogen bonds. Furthermore, formation of catenane (DB24C8)2-(3a) can be switched off and on in a controllable manner by successive addition of KPF6 and 18-crown-6.     

Synthesis of [3]catenanes based on metal-directed self-assembly and pi-donor/pi-acceptor interactions

A metal-directed self-assembly of [3]catenanes in combination with pi-pi interactions was investigated. Ligands based on 4,4'-bipyridinium or 2,7-diazapyrenium were used in conjunction with dioxoaryl cyclophanes (4-6) and trans-PdCl2(CH3CN)2. The [3]catenanes show a dinuclear palladium 46-membered metallomacrocycle interlocked by two pi-complementary dioxoaryl macrocycles. [structure: see text].     

Synthesis and crystal structures of the dioxovanadium complexes [VO2L1] and [VO2L2]2

Two new oxovanadium complexes, [VO₂L¹] (I) and [VO₂L²]₂ (II), where L¹ and L² are the deprotonated forms of 4-bromo-2-[(2-diethylaminoethylimino)methyl]phenol (HL¹) and 4-bromo-2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol (HL²), respectively, have been synthesized and characterized by IR spectra and single crystal X-ray diffraction. The crystal of I is monoclinic: space group P2₁/n, a = 14.300(3), b = 7.010(2), c = 15.460(2) ?, ?? = 107.401(2)°, V = 1478.7(5) ?³, Z = 4. The crystal of II is monoclinic: space group P2₁/c, a = 7.270(2), b = 15.373(3), c = 11.893(3) ?, ?? = 99.302(2)°, V = 1311.8(5) ?³, Z = 2. Complex I is a mononuclear dioxovanadium(IV) complex. Complex II is a centrosymmetric dinuclear dioxovanadium(V) complex with a V...V distance of 3.117(2) ?. The Vatom in I is in a distorted square-pyramidal coordination, and that in II is in an octahedral coordination. The difference in the structures of the complexes is largely induced by the hydrogen bonds during the self-assembly process.     

Iodide-catalysed self-assembly of donor-acceptor [3]catenanes

Charged donor-acceptor [3]catenanes comprising the pi-accepting cyclobis(paraquat-4,4'-biphenylene) and pi-donating aromatic crown ether macrocycles have been prepared in high yields using thermodynamically controlled dynamic nucleophilic substitution.     

Chelating DTPA amphiphiles: ion-tunable self-assembly structures and gadolinium complexes

A series of chelating amphiphiles and their gadolinium (Gd(iii)) metal complexes have been synthesized and studied with respect to their neat and lyotropic liquid crystalline phase behavior. These amphiphiles have the ability to form ion-tunable self-assembly nanostructures and their associated Gd(III) complexes have potential as magnetic resonance imaging (MRI) contrast enhancement agents. The amphiphiles are composed of diethylenetriaminepentaacetic acid (DTPA) chelates conjugated to one or two oleyl chain(s) (DTPA-MO and DTPA-BO), or isoprenoid-type chain(s) of phytanyl (DTPA-MP and DTPA-BP). The thermal phase behavior of the neat amphiphiles was examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross polarizing optical microscopy (POM). Self-assembly of neat amphiphiles and their associated Gd complexes, as well as their lyotropic phase behavior in water and sodium acetate solutions of different ionic strengths, were examined by POM and small and wide angle X-ray scattering (SWAXS). All neat amphiphiles exhibited lamellar structures. The non-complexed amphiphiles showed a variety of lyotropic phases depending on the number and nature of the hydrophobic chain in addition to the ionic state of the hydration. Upon hydration with increased Na-acetate concentration and the subtle changes in the effective headgroup size, the interfacial curvature of the amphiphile increased, altering the lyotropic liquid crystalline structures towards higher order mesophases such as the gyroid (Ia3d) bicontinuous cubic phase. The chelation of Gd with the DTPA amphiphiles resulted in lamellar crystalline structures for all the neat amphiphiles. Upon hydration with water, the Gd-complexed mono-conjugates formed micellar or vesicular self-assemblies, whilst the bis-conjugates transformed only partially into lyotropic liquid crystalline mesophases.     

Double-salt formation in crystal structures containing [Co(en)3]Cl3

The structures of three racemic double salts of [Co(en)₃]Cl₃ (en is ethane-1,2-diamine, C₂H₈N₂), namely, bis[tris(ethane-1,2-diamine-κ²N,N′)cobalt(III)] hexaaquasodium(I) heptachloride, [Co(en)₃]₂[Na(H₂O)₆]Cl₇, bis[tris(ethane-1,2-diamine-κ²N,N′)cobalt(III)] hexaaquapotassium(I) heptachloride, [Co(en)₃]₂[K(H₂O)₆]Cl₇, and ammonium bis[tris(ethane-1,2-diamine-κ²N,N′)cobalt(III)] heptachloride hexahydrate, (NH₄)[Co(en)₃]₂Cl₇·6H₂O, have been determined, and the structural similarities with the parent compound, tris(ethane-1,2-diamine-κ²N,N′)cobalt(III) trichloride tetrahydrate, [Co(en)₃]Cl₃·4H₂O, are highlighted. All four compounds crystallize in the trigonal space group Pc1. When compared with the parent compound, the double salts show a modest increase in the unit-cell volume. The structure of the chiral derivative [Λ-Co(en)₃]₂[Na(H₂O)₆]Cl₇ has also been redetermined at cryogenic temperatures (120 K) and the disorder noted in a previous report has been accounted for.     

Unique self-assembly patterns based on thiacalix[4]arene-silver interactions

Novel self-assembled supramolecular networks were prepared by the interactions of thiacalix[4]arenes bearing simple alkyl groups on the lower rim (4×MeO-, 4×n-PrO-) with silver triflate. Contrary to the classical calix[4]arenes (with CH₂ bridges between the aromatic moieties), the presence of four sulfur atoms enables the formation of S-Ag-S connections between the individual molecules leading to the coordination topology so far unknown in calixarene chemistry. These systems form infinite 1-D coordination polymeric structures in the solid state, where the thiacalixarene moieties are preorganized in a side-by-side arrangement. Interestingly, the linear coordination polymers were obtained using both the conformational immobilised (4×n-PrO, cone, 1,3-alternate conformers) and the conformational mobile (4×MeO) thiacalix[4]arenes, which indicates the generality of this behaviour in thiacalixarene series.     

First oxalate-bridged pentanuclear [Cu(L)]3[Mn(ox)3]2 complexes: synthesis and magnetism

Two novel CuII3MnIII2 pentanuclear oxalato complexes have been synthesized and characterized, namely [Cu(L)]3[Mn(ox)3]2 [L = 1,10-phenanthroline(phen) and 2,2-bipyridyl(bipy)] where ox is the oxalate dianion. Based on i.r., elemental analyses and electronic spectra, thesecomplexesareassignedtoextendedoxalato-bridged structures consisting of two manganese(III) ions and three copper(II) ions, in which each manganese(III) has a distorted octahedral environment and each copper(II) ion a distorted square pyramidal environment. The temperature dependance of the magnetic susceptibility for [Cu(phen)]3[Mn(ox)3]2·4H2O was measured over the 4.2–300K range and the observed data indicates antiferromagnetic spin exchange interaction between the CuII and MnIII ions.     

Self-assembly,characterisation, and crystal structure of multinuclear metal complexes of the [2 x 3] and [3 x 3] grid-type

The self-assembly of new multimetallic complexes of grid-type architecture is described. The binding of a set of tris-terdentate ligands, 1 a-1 d, based on terpyridine-like subunits, with different octahedrally coordinated metal ions leads to the formation of species whose structure depends strongly on the ligand, the metal ion, the counterion, the solvent, and the reaction conditions. Under suitable conditions, the [3 x 3] grid was obtained from the reaction of ligand 1 a with zinc tetrafluoroborate and from ligand 1 b with mercury triflate. The other ligands led to the formation of mainly one compound of composition [M(6)L(5)](12+), which has the structure of an incomplete [2 x 3] grid. The crystal structure of such a [2 x 3] grid, [Co(6)(1 d)(5)](12+), has been determined. In this complex, the three central pyrimidine-pyridine-pyrimidine non-coordinating sites adopt transoid NCbond;CN conformations. The much less stable cisoid conformations, the "pinching" of the coordination sites in the complex, the weaker donor strength of the central binding site, and the steric demand of the substituents are all factors contributing to the reluctance to produce the [3 x 3] structure. A subtle interplay between the nature of the metal, the steric demand of the ligand, the reaction conditions, and the type of counterion determine the product of self-assembly. The results obtained show that by tuning the parameters, complexes containing six or nine octahedrally coordinated metal ions in a well-defined grid-type arrangement are accessible. Both types of arrays, [2 x 3] and [3 x 3 ], are of interest as self-assembled inorganic architectures of well-defined structure and nuclearity that may be suitable prototypes for selective information storage media.     

Synthesis and crystal structures of PrIII and NdIII complexes with the macrocyclic cavitand cucurbit[6]uril

The [{Pr(NO₃)₂(H₂O)₃}{Pr(NO₃)(H₂O)₄} (C₃₆H₃₆N₂₄O₁₂)](NO₃)₃·4H₂O and [{Nd(NO₃)(H₂O)₄} ₂(NO₃@C₃₆H₃₆N₂₄O₁₂)][Nd(NO₃)₆] complexes were prepared by heating a mixture of lanthanide nitrates, cucurbit[6]uril, and water in a sealed tube. X-ray diffraction study demonstrated that the metal atoms in the former complex are linked to the macrocycle through tridentate coordination of the portal oxygen atoms of cucurbit[6]uril to the praseodymium(III) cation. The neodymium(III) complex is the first example of lanthanide compounds with cucurbit[6]uril belonging to coordination polymers. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1511–1517, September, 2006.     

Cyanocalix[4]arenes: synthesis,crystal structures and reactivity studies

Abstract

Herein, we describe an improved method to synthesise mono-, di- and tetra-cyanocalix[4]arene and report their crystal structure determinations. We also report our attempts to further functionalise the cyanocalix[4]arenes into dithiadiazolyl-calix[4]arenes, and propose a hypothesis as to why the cyano group on a calix[4]arene is an extremely challenging group to modify.     

Five dinuclear iron carbonyl complexes based on substituted tetramethylcyclopentadienyl ligands: synthesis and crystal structures

Thermal treatment of the substituted tetramethylcyclopentadienes [C₅Me₄HR] [R?=?n-propyl (1), i-propyl (2), cyclopentyl (3), cyclohexyl (4), and 4-NMe₂Ph (5)] with Fe(CO)₅ gave five new substituted tetramethylcyclopentadienyl dinuclear iron carbonyl complexes, [η⁵-C₅Me₄CH₂CH₂CH₃]₂Fe₂(CO)₄ (6), [η⁵-C₅Me₄CH(CH₃)₂]₂Fe₂(CO)₄ (7), [η⁵-C₅Me₄CH(CH₂)₄]₂Fe₂(CO)₄ (8), [η⁵-C₅Me₄CH(CH₂)₅]₂Fe₂(CO)₄ (9), and [(η⁵-C₅Me₄)(4-NMe₂Ph)]₂Fe₂(CO)₄ (10). The new complexes were characterized by elemental analysis, IR, and ¹H NMR spectra. The molecular structures of 6, 8, 9, and 10 were determined by X-ray single crystal diffraction.     

Pyrazolate-based copper(II) and nickel(II) [2 x 2] grid complexes: protonation-dependent self-assembly, structures and properties

The pyrazole-based diamide ligand N,N'-bis(2-pyridylmethyl)pyrazole-3,5-dicarboxamide (H(3)L) has been structurally characterised and successfully employed in the preparation of [2 x 2] grid-type complexes. Thus, the reaction of H(3)L with Cu(ClO(4))2.6H(2)O or Ni(ClO(4))2.6H(2)O in the presence of added base (NaOH) affords the tetranuclear complexes [M(4)(HL(4))].8H(2)O (1: M = Cu, 2: M = Ni). Employment of a mixture of the two metal salts under otherwise identical reaction conditions leads to the formation of the mixed-metal species [Cu(x)Ni(4-x)(HL)(4)].8H(2)O (x相似文献   

Synthesis and crystal structures of novel calix[4]azacrowns

A series of novel 1,3‐altemate calix[4]arene azacrowns having mono and bis crown ethers on the lower rim of the calix[4]arene framework were synthesized. Solid‐state structures confirmed the three dimensional conformation of compounds 1–3.     

Tetrathiafulvalene based electroactive ligands and complexes: Synthesis,crystal structures and antifungal activity

The synthesis of two tetrathiafulvalene-appended pyridinehydrazone pyrimidine ligands, namely (Z)-4-(2-((5-([2,2′-bi(1,3-dithiolylidene)]-4-yl)pyridin-2-yl)methylene) hydrazinyl)-6-chloropyrimidine L1 and (Z)-4-(2-((6-([2,2′-bi(1,3-dithiolylidene)]-4-yl)pyridin-2-yl)methylene) hydrazinyl)-6-chloropyrimidine L2 is described. Ligand L1 was reacted with cobalt(II) to yield a cationic metal complex [Co(L1)₂] while ligand L2 was reacted with zinc(II) to afford a neutral metal complex [ZnL2Cl₂]. The crystal structure analysis of [Co(L1)₂] indicate that Co(II) ion is coordinated by six nitrogen atoms from two perpendicular ligands while in [ZnL2Cl₂], Zn(II) is coordinated by two chlorine atoms and three nitrogen atoms. The electrochemical behavior indicate that ligands L1 and L2 and the zinc(II) complex are suitable fort the preparation of crystalline radical cation salts. Finally the determination of MIC₈₀ values against C. albicans, C. glabrata, C. parapsilosis, C. krusei and E. dermatitidis revealed that the cobalt(II) metal complex [Co(L1)₂] is active against all the studied fungi.     

Synthesis and alkali metal cation complexation ofN-aryl [3.2.2] cryptands

Two novel three-nitrogen cryptands withN-aryl substituents are prepared by cyclization of 1, 10-diaza-18-crown-6 with mixed anhydrides of 6-arylaza-3,9-dioxadecanedioic acid followed by borane reduction of the resultant bicyclic diamides. For the alkali metal cations, theN-phenyl [3.2.2] cryptand exhibits strongest complexation for Rb⁺ in picrate extractions.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.