Diazacrown Ethers Research Articles

Catalytic Capacity of Diaza-Crown Ether Lanthanum Complexes with Varied Ligands for Phosphate Ester Hydrolysis in Different Media

Two diaza-crown ether compounds, 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (L0) and its derivative with double acetamide side arms 2,2'-(1,4,10,13-teteaoxa-7,16-diazacyclooctadecane-7,16-diyl)diacetamide (L), and the corresponding two lanthanum complexes were synthesised and characterised. The catalytic capacity of the lanthanum complexes was investigated for the hydrolysis of bis(4-nitrophenyl) phosphate ester (BNPP) in aqueous solution and in CTAB micelles. Kinetic studies show that the catalytic efficiency of complex LaL is obviously higher than that of complex LaL0, and introducing acetamide into the ring of the diaza-crown ether can improve the catalytic ability of the complexes for BNPP hydrolysis. A rate enhancement of about two times was observed for the complex–micelle in contrast with the complex–water system for BNPP catalytic hydrolysis. The optimal pH for the catalytic reaction in the two kinds of media systems show an approximately 0.4 pH unit difference. The two complexes possess higher thermostability, and are more stable in the micelle than in aqueous solution. Based on the results and their analysis, a catalytic mechanism with cooperation of acetamide is proposed.

Isolation of homoleptic platinum oxyanionic complexes with doubly protonated diazacrown cation

Doubly protonated diazacrown ether cation (1,4,10,13-tetraoxa-7,16-diazoniacyclooctadecane DCH22+) was used for the efficient isolation of the homoleptic platinum complexes [Pt(NO3)6]2- and [Pt(C2O4)2]2- to crystalline solid phases from solutions containing mixtures of related platinum complexes. DCH22+ molecules in nitric acid solution were shown to prevent the condensation of mononuclear [Pt(H2O)n(NO3)6-n]n−2 species.

Comparison of catalytic activities of new La (III) and Ce (III) complexes with different diaza-crown ether ligands for DNA hydrolytic cleavage

A new diaza-crown ether with double hydroxypropyl branches (L = 1,1'-(1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyl)dipropan-2-ol) and its two lanthanide complexes (LaL and CeL) were synthesised and characterised. Their nuclease activities on pUC19 DNA cleavage were investigated using agarose gel electrophoresis, and pseudo-first-order rate constants kobs of 0.067 h–1 for LaL, 0.041 h–1 for CeL, 0.013 h–1 for LaL0, and 0.027 h–1 CeL0 were obtained (L0 = 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane). The results indicated that the CeL complex was more efficient than the LaL complex for DNA cleavage at low concentrations, but the LaL complex was more efficient than the CeL complex at high concentrations. Moreover, kinetic studies demonstrated that introducing hydroxypropyl side arms in the ring of the diaza-crown ether can improve the catalytic ability of the complexes in DNA cleavage, which may be due to the hydroxypropyl side arms enhancing the bonding interaction between the complex and the DNA molecule by hydrogen bonding. A hydrolytic mechanism for DNA cleavage was demonstrated by applying several oxygen scavengers to the DNA catalytic cleavage. A proposed mechanism for the DNA cleavage shows that the hydroxypropyl side groups can recognise and bind the phosphodiester bond of DNA by hydrogen bonding and electrostatic interaction.

The functionalization of magnetite nanoparticles by hydroxyl substituted diazacrown ether, able to mimic natural siderophores, and investigation of their antimicrobial activity

In this work we report of functionalization of magnetite nanoparticles by hydroxyl containing diazacrown ether—macroheterocycle (MC) that is able to mimic the properties of natural siderophores. The structure of synthesized crown ether was investigated by NMR, mass-, FTIR spectroscopy methods. The morphology of prepared MC@Fe3O4 nano-ensembles was analysed by scanning electron microscopy SEM, X-ray diffraction XRD analysis methods. The quantitative analysis of nanostructures was determined by atom absorbance spectroscopy as well as on the basis of Lambert–Beer law by UV spectroscopy method. It was found that the synthesized compounds were effective against gram-negative microorganisms Escherichia coli, Klebsiella spp. and gram-positive Staphylococcus aureus, having multi drug resistance properties.

DNA binding and cleavage properties of the Ce (III) complex of a diaza-crown ether

The hydrolytic cleavage of pUC19 DNA as promoted by the trivalent cerium complex (CeL) of diaza-crown ether ligand L (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane) was examined in detail. The interaction of CeL with calf thymus DNA was investigated by UV-Vis spectroscopy. Furthermore, studies on the effects of pH, reaction time, and the concentration of CeL on cleavage of pUC19 DNA were carried out by gel electrophoresis. The results indicate that CeL can bind to DNA electrostatically with a binding constant of 2.18x104 M−1; CeL can promote the cleavage of plasmid pUC19 DNA from supercoiled to the nicked form under the appropriate conditions, and the optimal pH value is 7.54. The lack of effect of radical scavengers indicates that the cleavage involves hydrolytic cleavage.

Diphenhydramine Compact-Cell Sensor

The construction and performance characteristics of a novel (diphenhydramine) DPH CC-sensor based on DZCE were reported in this work. The CC-membrane was prepared by incorporating of (diazacrown ether) DZCE and/or (tetraflorophenyl borate) TFPB into a plasticized poly(vinyl chloride) membrane. The CC-sensor revealed a Nernstian behavior over a DPH-concentration range (9.1 × 10-3 - 6.3 × 10-7 mol ·L-1), and relatively low detection limit (1 × 10-7 mol ·L-1). The potentiometric response was independent on the pH of the solution in the range of 7 - 10. The DPH-CC showed a very short response time (<5 s). It showed good selectivity towards different cations and pharmaceutical compounds. The relative selectivity coefficient was applied for evaluation of the selectivity properties of the DPH-CC. The DPH-CC was used successfully for determination of DPH in its samples. The found recovery range was 95% - 98.5%, and the standard deviation value ranged between 0.13 - 0.42. The DPH-CC facilitates the analysis of DPH directly without pretreatment and it can be built-in as a detector in chromatographic apparatus. It can be used as a tool for on-line monitoring of the drug levels.

A hydrogen bonded Co(ii) coordination complex and a triply interpenetrating 3-D manganese(ii) coordination polymer from diaza crown ether with dibenzoate sidearms

The diaza crown ether dicarboxylate ligand, 4,4′-((1,7-dioxa-4,10-diazacyclododecane-4,10-diyl)bis(methylene)dibenzoate), L, forms a monomeric coordination complex of Co(II) ions, CoL(H2O)2·2H2O, 1, and a coordination polymer (MnL·H2O)n, 2, with Mn(II) ions under hydrothermal conditions. The monomeric coordination complex (structure 1) is polar with mirror symmetry and crystallizes in the non-centrosymmetric space group Cm. The mirror plane bisects the complex at the six-coordinate Co(II) ion, the two oxygen atoms of the crown moiety and the two oxygen atoms from coordinated water molecules. The coordinated water molecules take part in strong, linear hydrogen bonds with carboxylate oxygens provided by neighboring Co(II)–crown complexes resulting in a three-dimensional (1 : 1)n polar network in which the topology of the underlying 8-coordinated net is sqc3. The structure of 2 crystallizes in the orthorhombic Fdd2 space group as an infinite, polar triply interpenetrating three-dimensional network. The eight-coordinate Mn(II) ion coordinates two oxygen and two nitrogen atoms of the crown moiety, as well as single carboxylate O atom from each of two neighboring ligands. In both structures, the ligand assumes a flexed-wing bird shape, with the two benzoate sidearms of the crown moiety locked in a syn orientation. The metal ion elevated above the plane of the diaza-crown oxygen and nitrogen atoms. The diaza-crown moiety with its two benzoate sidearms has the peculiar property of forming an oriented crystal structure where the metal-crown vectors are oriented parallel to each other in the crystal. However, the structures are achiral, but the rigid crystal lattice prevents re-orientation of the structure through inversion. The coordination polymer (MnL·H2O)n, 2, is a 3-center uninodal net with ths (ThSi2) topology. Computational results using the density functional theory (DFT) calculations explain why the flexed-wing bird shape is the preferred and most stable ligand conformation for metal ion binding. Both structures demonstrate magnetic properties that are characteristics of the respective non-interacting isolated paramagnetic transition metal ions that are present.

1500483: Comparison of catalytic activities of new La(III) and Ce(III) complexes with different diaza-crown ethers ligands for DNA hydrolytic cleavage – ESI

1500483: Comparison of catalytic activities of new La(III) and Ce(III) complexes with different diaza-crown ethers ligands for DNA hydrolytic cleavage – ESI

Potentiometric, spectrophotometric and AM1d studies of the equilibria between silver(I) ion and diaza-crown ethers with anthraquinone moiety in various solvents

Complex formation and stability constants between silver(I) ion and diaza-12-crown, diaza-15-crown and diaza-18-crown ethers with anthraquinone moiety were determined in acetonitrile, methanol and propylene carbonate. It was found that complexes of 1:1 inclusion-type and 1:2 sandwich-type metal-to-ligand stoichiometry were formed. Species of higher complexity Ag2L32+ and Ag3L22+ were also found, depending on the ligand and solvent. This has been proved by both spectrophotometric and potentiometric methods. The energetically most favorable structures of the 1:1 metal-to-ligand complexes were calculated and visualized by the AM1d method at a semiempirical level of theory.

Copper and zinc complexes of a diaza-crown ether as artificial nucleases for the efficient hydrolytic cleavage of DNA

Copper and zinc complexes of a diaza-crown ether, serving as artificial nucleases, exhibited high nuclease activities towards the hydrolytic cleavage of DNA.

Synthesis of macrobicyclic compounds containing diazacrown ether moieties and ortho-aminobenzylic spacers

N,N´-Bis(2-bromobenzyl) diaza-15-crown-5 and -diaza-18-crown-6 ethers were obtained in high yields. Palladium-catalyzed amination of these compounds with equimolar amounts of linear polyamines and oxadiamines afforded a large number of macrobicyclic compounds. It was found that the structure of starting compounds is crucial for the formation of the target cryptands and that their yields can substantially be increased by using larger catalyst loadings.

Synthesis of a New Diaazacrown Ether Compound Interconnected with an Azacrown Ether and Decorated with a Long Lipophilic Chain

The synthesis of an original compound consisting of an azacrown ether interconnected with a diazacrown ether bearing an alkyl chain is described herein. This derivative is promising for numerous applications.

Pd-Catalyzed Amination in the Synthesis of a New Family of Macropolycyclic Compounds Comprising Diazacrown Ether Moieties

N,N'-bis(bromobenzyl) and N,N'-bis(halopyridinyl) derivatives of diaza-12-crown-4, diaza-15-crown-5 and diaza-18-crown-6 ethers were synthesized in high yields. The Pd-catalyzed macrocyclization reactions of these compounds were carried out using a variety of polyamines and oxadiamines were carried out to give novel macrobicyclic and macrotricyclic compounds of the cryptand type. The dependence of the yields of macropolycycles on the nature of the starting diazacrown derivatives and polyamines was established. Generally N,N'-bis(3-bromobenzyl)-substituted diazacrown ethers and oxadiamines provided better yields of the target products. The highest yield of the macrobicyclic products reached 57%.

Synthesis of Trismacrocyclic and Macrotricyclic Compounds Possessing Structural Fragments of Aza- and Diazacrown Ethers, Cyclen and Cyclam via Pd-Catalyzed Amination Reactions

Synthesis of trismacrocyclic compounds with a central tetraazamacrocyclic moiety and two aza-crown ether fragments was carried out using the Pd-catalyzed amination of trans-bis(bromobenzyl) substituted cyclen and cyclam with 3 equiv. of azacrown ethers. The yields were shown to be dependent on the nature of the starting tetraazamacrocycles and reached 45 % in the best case. Formation of the cylindrically-shaped cryptands was achieved by reacting equimolar amounts of trans-bis(bromobenzyl) substituted cyclen or cyclam and diazacrown ethers. The yields of the target cryptands reached 30 % and a clear dependence of the result of the reaction on the reciprocal position of two bromine atoms and two nitrogen atoms in the reactants was observed.

Copper-catalyzed amination in the synthesis of polyoxadiamine derivatives of aza- and diazacrown ethers

Cu(I)-Catalyzed amination of N-(iodobenzyl) substituted azacrown ethers with propane-1,3-diamine and several polyoxadiamines was investigated. In the case of diamine excess and the use of CuI/l-proline catalytic system in EtCN the formation of the compounds with one azacrown and one diamine moieties was observed. When taking the excess of N-(iodobenzyl) derivative of azacrown ether and CuI/2-(isobutyryl)cyclohexanone catalytic system in DMF, bis(azacrown) substituted oxadiamine could be obtained. Amination of N,N’-di(iodobenzyl) substituted diazacrown ether was studied under the same conditions. The comparison of Pd(0)- with Cu(I)-mediated amination reactions was done using N-(bromobenzyl) substituted azacrown ethers.

Water soluble diaza crown ether derivative: Synthesis and barium complexation studies

The combination of a mcrocyclic cavity with o-diaminobenzene derivative offers a new redox-active and water-soluble ligand for barium that incorporates 12 potential donors. The chelator was synthesized in four steps from diaza-18-crown-6-ether and fully characterized in solution by cyclic voltammetry, UV–Visible and NMR spectroscopies in the presence of barium. The corresponding complex exhibits a 1:1 stoichiometry in solution whereas it crystallizes as 3:2 (M:L) as evidenced by X-ray diffraction studies. The high affinity constant for barium estimated by NMR and electronic absorption techniques in aqueous medium, makes this ligand a promising candidate for redox-induced barium release.

Naphthaldehyde-derived ligands: synthesis and their Ni(II) ion complexation

Three novel diazacrown ether ligands, namely 17-, 18-, and 20-membered O2N2-donor macrocycles derived from 3,3′-[butane-1,4-diylbis(oxy)]bis(2-naphthalenecarbaldehyde), were prepared and characterized by 1H and 13C NMR spectroscopy and mass spectra. Their host–guest interaction with Ni(II) was studied in DMSO-d 6 using 1H NMR spectroscopy. The stoichiometry of the complex in each case in the concentration range examined was determined to be 1:1 using the continuous variation method (Job’s plot). The 17-membered O2N2-donor macrocycle in which the two nitrogen atoms are tethered by three methylene units binds Ni(II) more strongly than the other two macrocycles do.

Synthesis of Macropolycycles Comprising Diazacrown and Adamantane Moieties via Pd -Catalyzed Amination Reaction

N,N’-bis(bromobenzyl) substituted diazacrown ethers were obtained in the reactions of corresponding free diazacrowns with two equivalents of bromobenzyl bromides in high yields. These compounds were introduced in the Pdcatalyzed amination reaction with 1,3-bis(aminomethyl) and 1,3-bis(2-aminoethyl)adamantanes to give macrobicyclic products. The yields were shown to be dependent on the nature of starting diazacrown derivatives and diamines. N,N’bis(3-bromobenzyl) substituted diazacrown ethers provided better yields of the target macrobicycles than N,N’-bis(4bromobenzyl) derivatives. In the latter case substantial amounts of cyclic oligomers were formed and isolated.

Potentiometric and AM1d studies of the equilibria between silver(I) and diaza-15-crown and diaza-18-crown ethers with nitrogen in different positions in various solvents

Complex formation and stability constants between typical and atypical diaza-15-crown and diaza-18-crown ethers with silver(I) were determined in methanol, acetonitrile and propylene carbonate by the potentiometric method. In two of the diaza crown ethers, AA-diaza-15 and AA-diaza-18-crown, two nitrogens in the macrocyclic ring replaced two consecutive oxygens instead of two opposite ones in the two other diaza crown ethers. It was found that complexes of 1:1 and 1:2 metal-to-ligand stoichiometry were formed. The solvent composition and cavity size of crown ethers significantly influences the stability constants of complexes. AA-diaza-15 and AA-diaza-18-crown ethers were examined for comparison with diaza-15-crown and diaza-18-crown ethers. AA-diaza crown ethers formed less stable 1:1 metal-to-ligand complexes with silver(I) than typical diaza crown ethers but their ability to form 1:2 metal-to-ligand complexes was stronger. The energetically most favorable structures of the 1:1 metal-to-ligand complexes were calculated and visualized by the AM1d method at the semiempirical level of theory.

Specific Cooperative Effect of a Macrocyclic Receptor for Metal Ion Transfer into an Ionic Liquid

An intramolecular cooperative extraction system for the removal of strontium cations (Sr(2+)) from water by use of a novel macrocyclic receptor (H(2)βDA18C6) composed of diaza-18-crown-6 and two β-diketone fragments in ionic liquid (IL) is reported, together with X-ray spectroscopic characterization of the resulting extracted complexes in the IL and chloroform phases. The covalent attachment of two β-diketone fragments to a diazacrown ether resulted in a cooperative interaction within the receptor for Sr(2+) transfer, which remarkably enhanced the efficiency of Sr(2+) transfer relative to a mixed β-diketone and diazacrown system. The intramolecular cooperative effect was observed only in the IL extraction system, providing a 500-fold increase in extraction performance for Sr(2+) over chloroform. Slope analysis and potentiometric titration confirmed that identical extraction mechanisms operated in both the IL and chloroform systems. Extended X-ray absorption fine structure spectroscopy revealed that the average distance between Sr(2+) and O atoms in the Sr(2+) complex was shorter in IL than in chloroform. Consequently, Sr(2+) was held by H(2)βDA18C6 more rigidly in IL than in chloroform, representing an important factor dominating the magnitude of the intramolecular cooperative effect of H(2)βDA18C6 for Sr(2+). Furthermore, competitive extraction studies with alkaline earth metal ions revealed that the magnitude of the intramolecular cooperative effect depended on the suitability between metal ion size and the cavity size of H(2)βDA18C6. Sr(2+) was successfully recovered from IL by controlling the pH in the receiving phase, and the extraction performance of H(2)βDA18C6 in IL was maintained after five repeated uses.