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1.
We have studied the peculiarities of complex [Zn(PM–PEA)2(NCS)2], which presents large void cavities. As powder it does not show solvent inclusion, while as single crystals we have evidenced the existence of various polymorphs, with and without solvent inclusion. These results are preliminary results for the comprehension of the behaviour of mixed [FexZn1?x(PM–PEA)2(NCS)2], where Zn has been used to decrease the cooperative interactions between Fe atoms and check the effects on the wide hysteresis reported for this compound.  相似文献   

2.
Two adamantane-1,3-dicarboxylato bridged cobalt(II) phenanthroline complexes [Co2(H2O)2(phen)2(adc)2]·(C2H7N)·2H2O (1) and [Co(H2O)(phen)(adc)]·H2O (2) were synthesized in a mixed solvent under 45 °C (H2adc = adamantane-1,3-dicarboxylic acid). Compound 1 consists of dinuclear [Co2(H2O)2(phen)2(adc)2] complex molecules, dimethylamine (C2H7N) molecules and hydrogen-bonded water molecules. The dinuclear molecules, via intermolecular hydrogen bonds, are interconnected into hydrogen-bonded chains along [1 0 0] and interdigitation of phen ligands due to interchain π?π stacking interactions assembles the hydrogen-bonded chains into 2D supramolecular layers parallel to (0 0 1). In compound 2, the Co(II) ions are bridged by adamantane-1,3-dicarboxylate anions to form 1D chains along [0 0 1], and the resulting chains are assembled into double-chains based on interchain π?π interactions. The double-chains are further held together via hydrogen bonds into 2D supramolecular layers parallel to (1 0 0). The variable temperature magnetic measurements show an overall weak antiferromagnetic behavior for 1, and an weak ferromagnetic behavior over 300-75 K followed by antiferromagnetic behavior below 75 K for 2.  相似文献   

3.
The macrocyclic ligand cyclam occurs as a 70:30 mixture of its trans-I and trans-II configurations, respectively, when included as its CuII complex inside the cavity of the macrocyclic host compound cucurbit[8]uril. This is the first report of an unsubstituted cyclam occurring in either of these two relatively high-energy configurations in the solid state. By comparison, NiII(cyclam) included in CB[8] in the solid state has been shown in the literature to exist in the more stable and much more common trans-III configuration. The existence of the CuII(cyclam) guest in the high-energy trans-I configuration as the major isomer is postulated to be the result of the supportive nature of the CB[8] cavity, resulting from specific hydrogen bonding between the cyclam amine hydrogens and the carbonyl groups of the CB[8] host. This solid CuII(cyclam)@CB[8] host-guest inclusion structure also exhibits other interesting features, again distinguished from the previously reported NiII analog. The CB[8] hosts are only partially occupied in this solid structure, with one-third of the host cavities remaining empty. Those that are occupied show significant distortion of one of the two cavity portals, to accommodate hydrogen bonding. In addition, the CuII(cyclam) guest is found to reside off-centre, and to partially extend outside of the CB[8] cavity, in order to optimize hydrogen bonding interactions.  相似文献   

4.
Redox-responsive vesicles self-assembled by supramolecular cyclodextrin amphiphiles, consisting of the guest (N-1-decyl-ferrocenylmethylamine, 1) and the host (2-O-carboxymethyl-β-cyclodextrin, CM-β-CD), were prepared. The morphologies and sizes of these novel vesicles in an aqueous solution were observed by transmission electron microscopy (TEM) and were confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS) measurements. The effects of the host-guest ratio, the concentration and the solvent composition of water and methanol on vesicles were investigated in detail. The interactions between the host and the guest, the complex stoichiometry, the stability constant and conformations of 1·CM-β-CD in aqueous solution were investigated by cyclic voltammetry (CV), UV and nuclear magnetic resonance (NMR) measurements. According to the complex stoichiometry and ‘tadpole-like’ spatial conformations, the supramolecular cyclodextrin amphiphiles made from 1·CM-β-CD were proposed to form the membranes of the vesicles. This kind of vesicle system was responsive to an oxidizing agent, which could pave the way to combine supramolecular host-guest chemistry and membrane chemistry for potentially functional applications.  相似文献   

5.
A series of mono- and oligonuclear vanadium(V) and vanadium(IV) complexes containing various chelating N,O-, N3-, and O2-ligands have been prepared. The biphasic reaction of an aqueous solution of ammonium vanadate and a dichloromethane solution of hexamethylphosphoramide (hmpa) and pyrazine-2-carboxylic acid (pcaH) or pyrazine-2,5-dicarboxylic acid (pdcaH2) or pyridine-2,5-dicarboxylic acid (pycaH2) yields yellow crystals of [VO2(pca)(hmpa)] (1), [(VO2)2(pdca)(hmpa)2] (2), and [VO2(pycaH)(hmpa)] (3), respectively. The single-crystal X-ray structure analyses reveal 1 and 3 to be mononuclear vanadium(V) complexes, in which a VO2 unit coordinates to one nitrogen and one oxygen atom of a pca or pycaH chelating ligand, and 2 to be a dinuclear vanadium(V) complex, in which two VO2 units are coordinated through one nitrogen and one oxygen atom of a pdca bridging ligand; in the three complexes the vanadium atoms also coordinate to the oxygen atom of a hmpa ligand. The reaction of N,N,N,N-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane (hptbH) and VOSO4 in methanol gives the cationic complex [(VO)4(hptb)2(μ-O)]4+ (4), which can be crystallized as the perchlorate salt. In this tetranuclear complex, two dinuclear vanadium(IV) units are held together by a μ-oxo bridge. The known complex [VOCl2(tmtacn)] (5) was synthesized from the reaction of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) and VCl3 in acetonitrile; the reaction of tetrabutylammonium vanadate with pyro-cathecol (catH2) in acetonitrile gives the known anionic complex [V(cat)3] (6), in which the vanadium(V) center is bonded to three cat chelating ligands through the oxygen atoms, obtained as the tetrabutylammonium salt. All compounds synthesized are highly efficient oxidation catalysts for the reaction of cyclohexane with air and hydrogen peroxide in the presence of four equivalents of pcaH per vanadium, although the catalytic activity of the complexes containing bulky chelating ligands 4 and 5 is somewhat lower in the initial period of the reaction. During this period the active species are formed from the complexes and final turnover numbers are high. The catecholate ligands of complex 6 may reduce from V(V) to V(IV) in the beginning of the process, thus providing very high initial oxidation rates.  相似文献   

6.
Reversible vesicles based on supramolecular inclusion of hydroxypropyl-β-CD (HPβCD) and N,N′-bis(ferrocenylmethylene)-diaminohexane (BFD) were prepared in water and methanol-water mixtures. The inclusion stoichiometry of HPβCD with BFD was in a molar ratio of 2:1, which could be named as ‘two head’ supramolecular amphiphile when the solvent was water. However, the inclusion stoichiometry of HPβCD with BFD would tend to be a molar ratio of 1:1 based on introduction of methanol to the solvent, especially when the volume ratio of methanol and water was more than 1:4, which could be named as ‘one head’ supramolecular amphiphile. The inclusion compounds could switch between ‘one head’ and ‘two head’ conformations by changing the methanol concentration of the solvents. The vesicles were also found to be responsive to the stimulus of external molecules. When the inclusion ability between HPβCD and an external guest was relatively stronger, the vesicles were easily destroyed. Furthermore, the vesicles disappeared after adding an oxidizing agent. NMR was used to confirm the conformation of the mixture of HPβCD and BFD in water. The structure and morphology of the vesicles were characterized by TEM and DLS. The vesicles may be used in smart materials, drug delivery and molecular recognition.  相似文献   

7.
Reaction of NH4VO3 with 2,6-pyridinedimethanol in water at 85 °C followed by the room temperature addition of HCl (aq) yields [HVO2(pydim)]x (pydim = 2,6-pyridinedimethanolato dianion), as a sparingly soluble off-white solid. This acid may be deprotonated by titration with NaOH (aq), yielding Na[VO2(pydim)] · 4H2O, which has been structurally characterized by single-crystal X-ray diffraction. Treating Na[VO2(pydim)] · 4H2O with HCl (aq) regenerates [HVO2(pydim)]x, but reaction with additional NaOH (aq) displaces the pyridinedimethanolato ligand from the vanadium center. Similarly, treating [HVO2(pydim)]x with excess HCl (aq) strips the pyridinedimethanolato ligand from the vanadium center and yields the adduct [H3(pydim)]+Cl as one component in a mixture of products. This adduct has been structurally characterized by single-crystal X-ray diffraction. The optimum pH range for stable dioxovanadium(V) complexes stabilized by the 2,6-pyridinedimethanolato ligand is at least 1.5-9.4.  相似文献   

8.
Although the 2,2′-biphenyldicarboxylate ligand (2,2′-dpa) has been widely used to construct metal-organic frameworks (MOFs) with helical sub-structure, the effect of the helical arrangement of spin carriers on the magnetic properties remains rarely scarce. In this article, two unique magnetic metal-organic supramolecular frameworks with different structural features, [Cu2(dpa)2(H2O)2(4,4′-dpdo)0.5]n (1) and [Ni(H2O)4(dpa)] · (4,4′-dpdo)(H2O) (2) (dpdo = 4,4′-dipyridine-N,N′-dioxide), have been isolated from the direct reaction of H2dpa with their corresponding salts in the presence of dpdo. In complex 1, the Cu-dpa double-helical chains, which are bridged by long flexible μ2-dpdo ligands to give rise to a regular 63 covalent layer, exhibit strong antiferromagnetic coupling interactions. Whereas the 1D [Ni(dpa)]n helical chains in complex 2 exhibit weak antiferromagnetic coupling interactions. Rich hydrogen bonds between perpendicular 1D [Ni(dpa)]n helical chains and quasi-1D (dpdo)n chains result in an intricate 3D supramolecular network.  相似文献   

9.
A dioxomolybdenum(VI) complex bearing the diimine ligand N,N′-bis(ferrocenylmethylene)ethylenediamine (FcNN) has been prepared in good yield by the reaction of FcNN with MoO2Cl2(THF)2. One isomeric form was identified by 1H NMR (including NOE experiments), corresponding to the cis,cis geometry with respect to the CN bonds of the free ligand. The polynuclear complex was immobilized in permethylated β-cyclodextrin (TRIMEB) by addition of the guest to a solution of TRIMEB in a mixture of dichloromethane and nitromethane. Removal of the solvent led to the isolation of an inclusion compound with a 2:1 host:guest stoichiometry. For comparison, an inclusion compound containing just the ligand FcNN and TRIMEB was prepared using a similar method. The products were characterized in the solid state by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FT-IR and 13C CP MAS NMR spectroscopy. UV-Vis measurements were also carried out in solution. Both the complex MoO2Cl2(FcNN) and its inclusion compound with TRIMEB catalyze with high selectivity the liquid phase epoxidation of cyclooctene using tert-butyl hydroperoxide (TBHP) as the oxidant. In general, the catalytic behavior of the MoVI complex was not markedly affected by encapsulation in TRIMEB, although observed activities were slightly lower.  相似文献   

10.
Reaction of VOCl2 with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives in ethanol gave as products [VO(H2Am4DH)Cl2] (1), [VO(H2Am4Me)Cl2] · 1/2HCl (2), [VO(H2Am4Et)Cl2] · HCl (3) and [VO(2Am4Ph)Cl] (4). Upon the dissolution of 1-4 in water, oxidation immediately occurs with the formation of [VO2(2Am4DH)] (5), [VO2(2Am4Me)] (6), [VO2(2Am4Et)] (7) and [VO2(2Am4Ph)] (8). The crystal and molecular structures of 5 and 6 were determined. Complexes 5-8 inhibited glycerol release in a similar way to that observed with insulin but showed a low enhancing effect on glucose uptake by rat adipocytes.  相似文献   

11.
A novel tetrameric metal cluster, [La2(phen)3(2,3-pdc)(NO3)4(H2O)]2·(CH3OH)2 (2,3-pdcH2 = pyridine-2,3-dicarboxylic acid, phen = 1,10-phenanthroline), have been synthesized at room temperature from water-methanol mixture by mixing the reactants in stoichiometric ratio. 2,3-Pdc and their π?π interactions played a vital role on the construction of the core. The auxiliary ligand, phen, which blocked the outermost periphery of the molecule and their hydrophobic π?π interactions facilitate the formation of the tetrameric metal clusters. The tetrameric metal clusters are connected by supramolecular interactions to form 3D supramolecular metal organic host (MOSH) producing supramolecular channels along a-axis. These supramolecular channels are filled up by solvent methanol molecules. The luminescent investigations reveal that cluster complex exhibits strong blue emission.  相似文献   

12.
This study aimed to improve the water solubility of 5,7-dimethoxyflavone (5,7-DMF) isolated from Kaempferia parviflora by complexation with 2-hydroxypropyl-β-cyclodextrin (HPβ-CD). The phase solubility profile of 5,7-DMF in the presence of HPβ-CD was classified as AL-type and indicated a 1:1 mole ratio. Differential scanning colorimetry, X-ray diffraction, NMR and SEM analyses supported the formation of a 5,7-DMF/HPβ-CD inclusion complex involving the A ring of 5,7-DMF inside the HPβ-CD cavity. This is the first example of CD inclusion with the A ring of non-hydroxyl flavones. The stability and binding constants of the complexes were determined using the phase solubility and UV-vis absorption spectroscopy, respectively. The water solubility of 5,7-DMF was increased 361.8-fold by complexation with HPβ-CD and overcame the precipitation problem observed in aqueous buffers, such as during in vitro anti-butyrylcholinesterase activity assays. The 1:1 mole ratio of the 5,7-DMF/HPβ-CD complex showed a 2.7-fold higher butyrylcholinesterase inhibitory activity (in terms of the IC50 value) compared to the non-complexed compound.  相似文献   

13.
《Inorganica chimica acta》1988,146(2):161-165
The compound [Cr(en)3][ZnCl4]Cl has been synthesized by reaction of CrCl3·6H2O, Zn and [Cr(en)3]2(SO4)3 in HCl. Its molecular and crystalline structure was determined by X-ray diffraction methods, being monoclinic, P21/c, a=21.215(3), b=12.532(2), c=13.707(2) Å, β=95.21°, V= 3629(2) Å3, Dx=1.738g cm−3, MW=474.9, Z= 8, F(000)=1928, λ(Mo Kα)=0.71069 Å, μ(Mo Kα)= 27.04 cm−1, 288 K. No significant exchange interactions between Cr(III) cations in the crystalline lattice were found. Curie-Weiss behavior was found in the three directions tested (g1=2.06±0.02,g2= 2.08±0.02,g3=2.09±0.01), T=1.2-1.4 K.  相似文献   

14.
《Inorganica chimica acta》2004,357(9):2763-2768
The new compound Cu(pn)2Ag2(CN)4 (CPAC; pn=1,2-diaminopropane) was isolated from a reaction mixture containing CuSO4, pn and K[Ag(CN)2] and was characterized by chemical analysis, IR and UV-VIS spectroscopy, and magnetic studies. The crystal structure of CPAC is built up of trinuclear NC-Ag-CN-Cu(pn)2-NC-Ag-CN molecules which are linked by hydrogen bonds and argentophilic interactions (Ag?Ag=3.26141(16) Å). The Cu(II) atom is coordinated in the equatorial plane by two chelate bonded pn ligands (mean Cu-N is 2.010(1) Å, while the axial positions are occupied by linear cyanoargentate anions acting as terminal ligands (Cu-N is 2.570(2) Å (2x)). The magnetic properties are well described by the Curie law down to 2 K.  相似文献   

15.
Magnetic interactions in binuclear copper(II) complexes, [Cu2(apyhist)2Cl2](ClO4)2 (1) and [Cu2(2-pyhist)2Cl2](ClO4)2 (2) with tridentate diimine ligands and chloro-bridged groups (where apyhist=(4-imidazolyl)ethylene-2-amino-1-ethylpyridine and 2-pyhist=(4-imidazolyl)ethylene-2-aminomethylpyridine) were studied with the aim of better elucidating magneto-structural correlations in such species, both in solution and in solid state. X-ray analyses revealed that chloro-bridged ligands keep the copper(II) ion coordinated to adjacent unit, at Cu-Cl distances of 2.271 and 2.737 Å, and a Cu-Cl-Cu angle of 87.46° in compound 1. Each CuII atom is also coordinated to three N atoms from the imine ligand, in a distorted tetragonal pyramidal environment. Magnetic measurements carried out in temperatures from 0.8 to 290 K and in magnetic field up to 170 kOe indicated that besides the intramolecular magnetic coupling between the copper centers [J/k=−(1.93±0.05) K] further interactions between adjacent dimers [Jz/k=−(1.3±0.1) K] should be taken into account. Similar results were observed for compound 2, for which [J/k=−(4.27±0.05) K] and [Jz/k=−(3.7±0.1) K]. In solution, the interconversion of the dimer 1 and the related monomer species [Cu(apyhist)(H2O)2] (ClO4)2 (3) monitored by EPR spectra, was verified to be very dependent on the solvent.  相似文献   

16.
The effect of substituent groups on asymmetric induction by β-cyclodextrin (β-CD) was investigated in the reduction of a series of o-, m-, and p-substituted acetophenones (X = H, Br, Cl, CH3, NO2, OCH3) with aqueous NaBH4. The inclusion of the ketones studied in β-CD led to water-insoluble compounds so that the reaction proceeded in the solid state. The substitutions resulted generally in higher enantioselectivities than that obtained for acetophenone indicating stronger host—guest interactions. Acetophenone and its m- and p-derivatives gave preponderantly the (?)-alcohol while the prevailing enantiomer was the (+)-alcohol in the case of the o-derivatives. The enantioface selectivity was found to be mainly governed by steric demands imposed by the size and the shape of the β-CD cavity in the case of the o-substituted acetophenones and by hydrophobic interactions in the case of the m-derivatives. A more complicated situation arose from the asymmetic reduction of p-derivatives where a combination of these factors with hydrogen bonding of the carbonyl group to the hydroxyls of β-CD are responsible for the enantioselectivity. © 1994 Wiley-Liss, Inc.  相似文献   

17.
Hydrothermal reaction of the carboxylate-based ligands with metal salts (or oxide) and 4,4′-bipyridine as a second linker, afforded three new coordination polymers, namely, [Co(PCPA)2(4,4′-bpy)]n (1) with 2-D rectangle grids, Cu(PCPA)2(4,4′-bpy)]n (2) with a linear chain, [Ag(PCPA)(PCPAH)(4,4′-bpy) · H2O]n (3) with 1-D molecular ladder (4,4′-bpy = 4,4′-bipyridine; PCPA = p-chlorophenoxyacetate; PCPAH = p-chlorophenoxyacetic acid). It is noticeable that compound 3 is also a supramolecular framework built by coordination bonds, weak interactions between Ag ions, π-π stacking interactions and hydrogen-bonded interactions. The three compounds with different structure motifs have been characterized by elemental analyses, IR spectra, ultraviolet-visible diffuse reflection integral spectra, fluorescent spectra and single crystal X-ray diffraction analysis. Furthermore, the bonding properties of compound 3 were investigated in terms of the absorption spectrum, as well as the calculated band structures and density of states.  相似文献   

18.
Reaction of M(OAc)2 (MII = CuII for 1, CoII for 2, and PbII for 3) with pyridine-2,6-dicarboxylic acid (H2pydc) in presence of a dipyridyl spacer 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) affords three novel metal-organic supramolecular networks [Cu2(bpo)(pydc)2(H2O)3] · 2.75H2O(1), [Co(bpo)(pydc)(H2O)2] · (H2O) (2) and [Pb(pydc)]n (3), which have been structurally determined by single-crystal X-ray diffraction. The dimeric Cu-pydc coordination framework bridged by a bpo spacer in 1 is hydrogen-bonded to four others to result in a two-dimensional (2-D) sheet array. The neutral monomeric molecules in 2 have an ordered 3-D stacking stabilized via hydrogen bonds and significant π-π interactions in the lattice, possessing large porous channels with the inclusion of guest solvates. In coordination polymer 3, the PbII ion takes the unusual distorted capped trigonal prismatic geometry (PbNO6) and each pydc dianion binds to four PbII centres to form a 2-D infinite network. The thermal stabilities of these complexes have also been investigated.  相似文献   

19.
Abstract

Cyclodextrins (CD's) have proved useful as model systems for the study of hydrogen bonding. They are torus-shaped molecules composed of six(α), seven (β) or eight(γ) (1?4) linked glucoses. Because of their particular geometry, they are able to act as a “host” to form inclusion complexes with “guest” molecules very much like enzymes. Cyclodextrins have been shown to exert catalytic activity on suitable included-substrate molecules; they catalyze the hydrolysis of phenylacetates, of organic pyrophosphates and of penicillin derivatives. They also accelerate aromatic chlorinations and diazo coupling by means of their primary and/or secondary hydroxyl groups, so that the rates of hydrolysis are enhanced by up to a factor of 400. In order to understand the hydrogen bonding in these enzyme models, neutron diffraction data were collected to unambiguously determine the hydrogen atom positions, which could not be done from the x-ray diffraction data. α-CD has been shown to have two different structures with well-defined hydrogen bonds, one “tense” and the other “relaxed”. An “induced-fit”-like mechanism for α-CD complex formation has been proposed. Circular hydrogen bond networks have also been found for α-CD due to the energetically favored cooperative effect. β-CD with a disordered water structure possesses an unusual flip-flop hydrogen bonding system of the type O-H…H-O representing an equilibrium between two states: O-H…O?O…O. γ-CD with a disordered water structure similar to β-CD also possesses the flip-flop hydrogen bond. This study demonstrates that hydrogen bonds are operative in disordered systems and display dynamics even in the solid state.  相似文献   

20.
Two new supramolecular compounds, [Ag(4,4′-bipy)]n [Ag(HBTC)]n (1) and [Cu(H2BTC)(2,2′-bipy)] (2) (HBTC/H2BTC = 1,2,4-benzenetricarboxylate, 4,4′-bipy/2,2′-bipy = 4,4′/2,2′-bipyridine), have been synthesized and characterized by elemental analyses, IR spectra, ultraviolet-visible diffuse reflection integral spectra (UV-Vis DRIS), fluorescent spectra, thermogravimetric analysis and single crystal X-ray diffraction analysis. It is noteworthy that there were two kinds of one-dimensional stairs-chain including cationic [Ag(4,4′-bipy)]n chain and anionic [Ag(HBTC)]n chain in 1. Furthermore, a two-dimensional double layer supramolecular framework was constructed through coordination bonds, hydrogen bonds, π-π stacking interactions and Ag?O weak coordinative interactions. The one-dimensional supramolecular chain of 2 was built from combining mononuclear [Cu(H2BTC)(2,2′-bipy)] by inter- and intra-molecular hydrogen bonding interactions. Additionally, the two complexes exhibit intense blue or olivine luminescence at room temperature.  相似文献   

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