Formation Of Coordination Complexes Research Articles

EXTRACTION OF NATURAL DYES FROM AFRICAN MARIGOLD FLOWER (TAGETES EREECTA L) FOR TEXTILE COLORATION

Abstract African marigold [Tagetes erecta L.], a major source of carotenoids and Lutin, is grown as a cut flower and a garden flower, in addition to being grown for its medicinal values. Marigold flowers [Tagetes ], which are yellow to orange red in colour, are a rich source of lutein, a carotenoid pigment. Nowadays, Lutein is becoming an increasingly popular active ingredient used in the Food Industry and Textile coloration [3].This pigment has acquired greater significance because of its excellent colour value. Although marigold flower extract has been used in veterinary feeds, the potential use of marigold as a natural textile colorant has not been exploited to its full extent. This is due to the lack of information on its safety, stability, and compatibility in textile coloration. In this study, an experiment was conducted to study the use of an extract isolated from marigold as a natural dye. The dye potential of the extract was evaluated by dyeing [6], using the flower, in 100 % cotton and silk fabrics under normal dyeing conditions. Studies of the dyeability, wash fastness, light fastness, and colour hue were undertaken [8,9,10]. The, L,a and 'b' of materials dyed using the extract were studied with the use of Computer Colour Matching software [9,10]. The surface colour was not affected by washing, and the quality of the flower was maintained even washing at 60o C for 30 minutes. Studies have indicated that the change of some of the colors have been noticed after washing with soap [8]. Most of the metal salts exhibited the highest K/S values, due to their ability to form coordination complexes with the dye molecules [1,2]. These findings reveal that the extract of Marigold flower can be used for coloration of !00 % cotton, silk, and wool fabrics. This article deals with the chemistry, processing, and stability of the pigment and its applications in textile coloration.

A vic -dioxime ligand bearing fluorescent coumarin moieties and its complexes; preparation, spectroscopy, and electrochemistry

The synthesis of a new vic-dioxime ligand, N,N′2-dihydroxy-O 1,O 2-bis(4-methyl-2-oxo-2H-chromen-7-yl)oxalimidamid (LH2) (1), bearing functional coumarins and its soluble mono- {Ni(II), Cu(II), Co(II)} and dinuclear {UO2(II)} complexes are presented. The fluorescence properties due to the 7-hydroxy-4-methylcoumarin fluorophore, which is conjugated with vic-dioxime that functions as the MN4 core of 1 and its complexes, are also reported. The formation of coordination complexes resulted in the blue shift in excitation spectrum and fluorescence quenching of 1. Both mononuclear {(LH)2M, M=Ni(II), Cu(II), and Co(II)} and homodinuclear {(LH)2(UO2)2(OH)2)} complexes have been obtained with metal : ligand ratios of 1 : 2 and 2 : 2, respectively. The characterizations of the new compounds were made by elemental analysis, 1H-NMR, FT-IR, UV-Vis, and LCMS data. Redox behavior of 1, involving oxime and coumarin moieties, and its complexes with Ni(II), Cu(II), Co(II) and UO2(II) were investigated by cyclic voltammetry. The comparison of the electrochemical behavior of 1 with its complexes enabled us to identify metal-, oxime- and coumarin-based signals.

Effects of Hydration on Mechanical Properties of a Highly Sclerotized Tissue

The jaws of the bloodworm Glycera dibranchiata consist principally of protein and melanin scaffolds with small amounts of unmineralized copper (Cu) and mineralized atacamite (Cu2Cl(OH)3) fibers in distinct regions. Remarkably, when tested in air, the regions containing unmineralized Cu are the hardest, stiffest, and most abrasion resistant. To establish the functions of jaw constituents in physiologically relevant environments, this study examines the effects of hydration on their response to indentation, scratching, and wear. Although all jaw regions are degraded by the presence of water, the ones containing unmineralized Cu are affected least. Notably, scratch depths in the bulk and the atacamite-containing regions double when wet, whereas the corresponding increase in the regions with unmineralized Cu is ∼20%. The results support the view that Cu ions are involved in the formation of intermolecular coordination complexes, creating a cross-linked molecular network that is both mechanically robust and resistant to water ingress. Hydration effects are greatest during wear testing, rates of material removal in water being about three times those in air. The mechanism underlying accelerated wear is suspected to involve coupled effects of near-surface damage and enhanced water ingress, resulting in increased plasticization and susceptibility to plastic plowing.

Syntheses, structures and luminescent properties of zinc(ii) and cadmium(ii) coordination complexes based on new bis(imidazolyl)ether and different carboxylate ligands

A series of mixed-ligand coordination complexes, namely [Zn(CA)(2)(BIE)] (1), [Zn(OX)(BIE)].H(2)O (2), [Zn(2)(m-BDC)(2)(BIE)(2)] (3), [Cd(m-BDC)(BIE)] (4), [Cd(5-OH-m-BDC)(BIE)] (5), [Zn(5-OH-m-BDC)(BIE)] (6), [Zn(2)(p-BDC)(2)(BIE)(2)].2.5H(2)O (7), [Cd(3)(p-BDC)(3)(BIE)] (8), [Cd(3)(BTC)(2)(BIE)(2)].0.5H(2)O (9) and [Zn(BTCA)(0.5)(BIE)] (10), where CA = cinnamate anion, OX = oxalate anion, m-BDC = 1,3-benzenedicarboxylate anion, 5-OH-m-BDC = 5-OH-1,3-benzenedicarboxylate anion, p-BDC = 1,4-benzenedicarboxylate anion, BTC = 1,3,5-benzenetricarboxylate anion, BTCA = 1,2,3,4-butanetetracarboxylate anion, and BIE = 2,2'-bis(1H-imidazolyl)ether, were synthesized under hydrothermal conditions. In 1, a pair of BIE ligands bridge adjacent Zn(II) atoms to give a centrosymmetric dimer. In 2 and 3, BIE ligands connect Zn(II)-carboxylate chains to form hexagonal honeycomb 6(3)-hcb and square 4(4)-sql layers, respectively. In 4 and 5, m-BDC and 5-OH-m-BDC bridge Cd(II) atoms to give dimeric units, respectively, which are further linked by BIE ligands to form sql nets. In 6, the BIE ligands extend the Zn(II)-carboxylate chains into 2D sinusoidal-like sql nets. The undulated sql nets polycatenate each other in the parallel manner with DOC (degree of catenation) = 2, yielding a rare 2D --> 3D parallel polycatenation net. In 7, the BIE and p-BDC ligands link the Zn(ii) atoms to give a rare 3-fold interpenetrated 3-connected 10(3)-ths net. 8 contains unusual edge-sharing polyhedral rods formed by [Cd(3)(CO(2))(6)] clusters. Each rod is connected by the benzene rings of p-BDC in four directions into a simple alpha-Po topology. In 9, two kinds of different 2D Cd-BTC layers are alternately linked to each other by sharing Cd(ii) centers to form a 3D framework, which is further linked by two kinds of BIE ligand to produce a complicated 3D polymeric structure. 10 possesses a unique (3,4)-connected 3D framework with (8(3))(2)(8(5).10) topology. The structural differences described indicate the importance of carboxylate ligands and metals in the framework formation of coordination complexes. The infrared spectra, thermogravimetric and luminescent properties were also investigated in detail for the compounds.

Preparation and characterization of polyesterurethane/copper metallopolymers

A series of metallopolymers (CuMP) were prepared from a MDI-based polyesterurethane and copper ions as chloride by using different initial molar ratios urethane groups/copper ions ranging from 180:1 to 12:1. CuMP and the parent polymer (PU) were analyzed by atomic absorption spectrometry (AAS), ultraviolet and visible (UV–vis) absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetry (TGA) and tensile testing. The copper ions form coordination complexes with the nitrogen atoms of the urethane groups, the intermolecular complexation resulting in the crosslinking of the hard segments; as a consequence, the destruction of the original hydrogen bonding and crystallinity of the hard-segment domains takes place. The differences in viscoelastic and mechanical behaviors shown by CuMP in comparison with PU (higher soft-segment glass transition, storage modulus and tensile strength, and lower elongation at break) reveal the reinforcing effect of copper ions on the polymer matrix. CuMP compared with PU exhibit lower initial thermal stability, the final stage of their thermal decomposition process is catalyzed, whereas the intermediate decomposition products are more thermally stable. The implications and mechanisms behind these observations are discussed.

A nonmineralized approach to abrasion-resistant biomaterials

The tooth-like mouthparts of some animals consist of biomacromolecular scaffolds with few mineral components, making them intriguing paradigms of biostructural materials. In this study, the abrasion resistance of the jaws of one such animal, the bloodworm Glycera dibranchiata, has been evaluated by nanoindentation, nanoscratching, and wear testing. The hardest, stiffest, and most abrasion-resistant materials are found within a thin (<3 microm) surface layer near the jaw tip and a thicker (10-20 microm) subsurface layer, both rich in unmineralized Cu. These results are consistent with the supposition that Cu ions are involved in the formation of intermolecular coordination complexes between proteins, creating a highly cross-linked molecular network. The intervening layer contains aligned atacamite [Cu(2)(OH)(3)Cl] fibers and exhibits hardness and stiffness (transverse to the alignment direction) that are only slightly higher than those of the bulk material but lower than those of the two Cu-rich layers. Furthermore, the atacamite-containing layer is the least abrasion-resistant, by a factor of approximately 3, even relative to the bulk material. These observations are broadly consistent with the behavior of engineering polymer composites with hard fiber or particulate reinforcements. The alignment of fibers parallel to the jaw surface, and the fiber proximity to the surface, are both suggestive of a natural adaptation to enhance bending stiffness and strength rather than to endow the surface regions with enhanced abrasion resistance.

Mordant dyes as sensitisers in dye-sensitised solar cells

Many mordant dyes commonly used in the textile industry form coordination complexes at the surface of nanocrystalline TiO 2. Dyes having a salicylate chelating group are particularly effective. Forty-nine commercial mordant dyes were studied as sensitisers in a non-optimised dye-sensitised solar cell (DSSC) and their performance compared to the N3 ruthenium complex. Although N3 produced the highest output, six mordant dyes produced photocurrents >0.2 mA. UV–visible spectra of the dye-complexed photoanodes suggest that some mordant dyes are more strongly bound to the TiO 2 surface than N3. Photocatalytic oxidation of these dyes does not appear to occur in a DSSC environment.

Reactions of Indene and Indoles with Platinum Methyl Cations: Indene C-H Activation, Indole π vs. Nitrogen Lone-Pair Coordination.

Reactions of indene and various substituted indoles with [(diimine)PtII(Me)(TFE)]+ cations have been studied (diimine = ArN = C(Me) - C(Me) = NAr; TFE = 2,2,2-trifluoroethanol). Indene displaces the TFE ligand from platinum to form a stable π coordination complex that, upon heating, undergoes C-H activation with first order kinetics, ΔH‡ = 29 kcal/mol, ΔS‡ = 10 eu, and a kinetic isotope effect of 1.1 at 60 °C. Indoles also initially form coordination complexes through the C2=C3 olefin, but these undergo rearrangement to the corresponding N-bound complexes. The relative rates of initial coordination and rearrangement are affected by excess acid or methyl substitution on indole.

Affinity monolith chromatography

The combined use of monolithic supports with selective affinity ligands as stationary phases has recently given rise to a new method known as affinity monolith chromatography (AMC). This review will discuss the basic principles behind AMC and examine the types of supports and ligands that have been employed in this method. Approaches for placing affinity ligands in monoliths will be considered, including methods based on covalent immobilization, biospecific adsorption, entrapment, and the formation of coordination complexes. Several reported applications will then be presented, such as the use of AMC for bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, dye-ligand affinity chromatography, and biomimetic chromatography. Other applications that will be discussed are chiral separations and studies of biological interactions based on AMC.

Synthesis, Characterization and the Antioxidative Activity of Copper(II), Zinc(II) and Nickel(II) Complexes with Naringenin

New complexes of Cu(II), Zn(II) and Ni(II) with naringenin have been synthesized and characterized on the basis of elemental analyses, molar conductivities, 1H-n.m.r., i.r. spectra, u.v. spectra, thermal analyses, and fluorescence spectra. In addition, the suppression ratio for O2−· (a) and OH· (b) of the complexes were studied by spectrophotometric methods. The results show that the effect of the Cu(II)-complex IC50 (a) = 0.003 μm, IC50 (b) = 0.06 μm is the most remarkable, and the average scavenger ability of the complexes (IC50=0.06–2.67μm) against OH· is higher than that of the ligand (IC50 = 28.5 μm). Taken together, these results indicate that the scavenger effect can be enhanced by the formation of metal-ligand coordination complexes, and the transition-metal ions may have differential and selective roles.

Metal‐ion‐mediated healing of gels

Self-healing is common in biological systems. A cut or a wound heals with time by cell migration from the adjacent tissues followed by cell proliferation and remodeling, leaving behind only a scar or weld line. Healing is also seen in synthetic linear polymers. Two pieces of polymers are welded by the reptation of chains across the interface at temperatures above the glass-transition or melting temperature. Unlike linear polymers, crosslinked polymeric networks cannot heal naturally because of the lack of reptation ability of the network chains across an interface. However, several smart ways for healing crosslinked polymers have been reported in the recent past. One of the techniques makes use of repair chemicals that are embedded in hollow fibers or microcapsules and that initiate self-repair when released during crack propagation. Another technique uses a reversible Diels– Alder chemistry, in which a furan and a maleimide react around 80 8C to reform a cracked network. The aforementioned strategies cannot be used to heal lightly crosslinked and water-swollen polymer networks because of their soft nature and the presence of water. In this work, we meet the challenge of demonstrating a healing phenomenon in hydrophilic gels. We show that certain hydrogels that have flexible hydrophobic side chains with a terminal carboxyl group undergo healing at the ambient temperature mediated by transition-metal ions. Healing occurs by the formation of coordination complexes that are much stronger than other noncovalent interactions such as chain entanglements and hydrogen bonding. The weld so formed then grows in strength with time, eventually leading to the process of metal-ion-mediated healing of the gels.

Synthesis and Structural Characterization of a New Heterobimetallic Coordination Complex of Barium and Cobalt for Use as a Precursor for Chemical Vapor Deposition

Ba(dmae)2 (dmaeH=N,N-dimethylaminoethanol, C4H11NO) reacts with Co(acac)2 (acac=2,4-pentanedionate) to produce the trinuclear coordination complex [Ba2Co(acac)4(dmae)3(dmaeH)] in an 85% yield. Spectroscopic and single-crystal X-ray diffraction experiments indicate that the complex possesses a structure in which two barium atoms and a cobalt atom are bridged by acac and dmae groups. The barium centers are eight and nine coordinate with BaO7N and BaO7N2 coordination spheres while the cobalt is a more regular CoO5N octahedron. This 2:1 heterobimetallic molecular complex was investigated as precursor for the deposition of thin film by AACVD. The film was characterized by SEM and XRD. TGA shows that the complex starts thermal decomposition upon heating in nitrogen atmosphere at 105 degrees C to produce barium cobalt oxide material of a Ba2CoO3 composition with an orthorhombic structure. The synthetic approach detailed here represents a unique route to the formation of a heterobimetallic barium cobalt coordination complex.

Hypoxia impedes the formation of chromium DNA-adducts in a cell-free system

The metabolic reduction of hexavalent chromium [Cr(VI)] in the presence of DNA generates several lesions which impede DNA replication and gene transcription. However, the relative contribution of molecular oxygen to Cr-induced genetic damage is unclear. To elucidate the role of dioxygen in Cr genotoxicity, we studied the formation of Cr-induced lesions in DNA treated with either Cr(VI) and the physiological reductant, ascorbic acid (Asc), or Cr(III), under ambient and hypoxic (<1% oxygen) conditions. We found that hypoxia did not impede the reduction of Cr(VI) by Asc throughout a 2 h treatment. In contrast, Cr-DNA binding under these conditions was reduced up to 70% by hypoxia, and a 50–90% decrease in the frequency of Cr-induced Taq polymerase-arresting DNA adducts was also observed. In the presence of Cr(VI)/Asc, formation of Cr-DNA interstrand crosslinks (ICLs) under hypoxia was 50% or less of that under ambient conditions. Kinetic studies found that hypoxia reduced the rate at which Cr interacted with DNA, but not the ultimate steady state level of Cr-DNA binding. The inhibitory effect of hypoxia on Cr(VI)/Asc genotoxicity could not be explained solely by alterations in the reactivity of intermediate Cr(V) species because Cr(III)-DNA binding and Cr(III)-induced ICL formation were also impaired by hypoxia. Moreover, Cr(V) was generated to similar levels in ambient and hypoxic reactions. Hypoxia did not affect ICL formation by the inorganic chemotherapeutic agent cisplatin, suggesting that these effects were specific for Cr(III). Taken together, these results support a role for dioxygen in facilitating the formation of Cr-DNA coordination complexes.

Role of second-sphere coordination in anion binding: Synthesis, characterization and X-ray structure of hexaamminecobalt(III) chloride hydrogen phthalate trihydrate and sodium hexaamminecobalt(III) benzoate monohydrate

In an effort to utilize [Co(NH 3) 6] 3+cation as a new host for carboxylate ions, orange coloured crystalline solids of composition [Co(NH 3) 6]Cl(C 8H 5O 4) 2·3H 2O ( 1) and Na[Co(NH 3) 6](C 7H 5O 2) 4·H 2O ( 2) were obtained by reacting hot aqueous solutions of hexaamminecobalt(III) chloride with potassium hydrogen phthalate and sodium benzoate in 1:3 molar ratio, respectively. The title complex salts were characterized by elemental analyses and spectroscopic studies (IR, UV/Visible and NMR). Single crystal X-ray structure determinations revealed the formation of second-sphere coordination complexes based on hydrogen bond interactions. In complex salt 1 only two out of three ionisable chloride ions present in [Co(NH 3) 6]Cl 3 were replaced by two C 8 H 5 O 4 − ions whereas in complex salt 2 all the three ionisable chloride ions present in [Co(NH 3) 6]Cl 3 were replaced and the final product was an adduct with another mole of sodium benzoate in solid state. The crystal lattice is stabilized by electrostatic forces of attraction and predominantly N–H⋯O interactions.

Dual Functionality of the Anti-β1 Integrin Antibody, 12G10, Exemplifies Agonistic Signalling from the Ligand Binding Pocket of Integrin Adhesion Receptors

Although integrins are known to mediate connections between extracellular adhesion molecules and the intracellular actin cytoskeleton, the mechanisms that are responsible for coupling ligand binding to intracellular signaling, for generating diversity in signaling, and for determining the efficacy of integrin signaling in response to ligand engagement are largely unknown. By characterizing the class of anti-integrin monoclonal antibodies (mAbs) that stimulate integrin activation and ligand binding, we have identified integrin-ligand-mAb complexes that exhibit differential signaling properties. Specifically, addition of 12G10 mAb to cells adhering via integrin alpha4beta1 was found to trigger disruption of the actin cytoskeleton and prevent cell attachment and spreading, whereas mAb addition to cells adhering via alpha5beta1 stimulated all of these processes. In contrast, soluble ligand binding to either alpha4beta1 or alpha5beta1 was augmented or unaffected by 12G10. The regions of the integrin responsible for differential signaling were then mapped using chimeras. Surprisingly, a chimeric alpha5 integrin containing the beta-propeller domain from the ligand binding pocket of alpha4 exhibited the same signaling properties as the full-length alpha4 integrin, whereas exchanging or removing cytoplasmic domains had no effect. Thus the mAb 12G10 demonstrates dual functionality, inhibiting cell adhesion and spreading while augmenting soluble ligand binding, via a mechanism that is determined by the extracellular beta-propeller domain of the associating alpha-subunit. These findings therefore demonstrate a direct and variable agonistic link between the ligand binding pocket of integrins and the cell interior that is independent of the alpha cytoplasmic domains. We propose that either ligand-specific transmembrane conformational changes or ligand-specific differences in the kinetics of transmembrane domain separation underlie integrin agonism.

Coordination Complexes of Copper in Mass Exchange of Biologically Active Substances

Special features of the interaction of copper with organic compounds containing groups (ligands) susceptible to the formation of coordination complexes are considered. Some general properties of copper-containing compounds are described, which determine the main physicochemical characteristics of such complexes. The behavior of coordination complexes of copper with said ligands in chromatographic systems is analogous to the behavior of coordination complexes of silver with olefinic compounds.

Tuning the topologies of MnII complexes with 3-(2-pyridyl)pyrazole and carboxylate ligands by intramolecular hydrogen bonds and the geometries of pendant ligands: crystal structures and magnetic properties

In our efforts to investigate the influence of intramolecular hydrogen bonding interactions and the geometries of pendant ligands on the structures of low-dimensional coordination architectures, two kinds of ligands have been selected: a) a chelating ligand, 3-(2-pyridyl)pyrazole (L1), with a non-coordinated nitrogen atom as a good hydrogen bonding acceptor and b) three pendant monocarboxylato ligands with different aromatic backbones (L2, L3 and L4) , and their MnII complexes, [Mn(L1)2(L2)2] (1), [Mn(L1)2(L3)2] (2) and [Mn2(L1)2(L4)4] (3), have been prepared and structurally characterized by single crystal X-ray diffraction analysis. The results show clearly that the chelating 3-(2-pyridyl)pyrazole ligand plays the dominant role in the adjustment of the modes of the monocarboxylate ligands through strong intramolecular hydrogen bonding interactions and results in the formation of low-dimensional coordination complexes. The geometry of the anthracene ring also plays a vital role in determining the topology of 3, which further affects the magnetic interactions between the metal centers.

Terpyridine copperii–polycarboxylic acid architectures: formation of dimeric, helical, and cyclic nanostructures and their included-water molecule motifs

New crystalline architectures have been prepared employing the propensity of terpyridine-CuII adducts to form coordination complexes with carboxylate moieties.

Formation of Hexagonal Coordination Complexes

AbstractThe synthesis of the ligand 1,3‐bis(3′‐pyridylethynyl)benzene and the coordination complex formed with copper(II) acetate is described. The complex is hexagonal with two ligands bridged by paddlewheel‐shaped dimeric copper(II) acetate moieties. The complexes are packed in such a way that the benzene rings from two separate complexes penetrate into the central cavity. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

Diffusion barrier properties of carboxyl- and amine-terminated molecular nanolayers

Molecular nanolayers are attractive for preserving the integrity of Cu-dielectric interface in sub-50nm interconnect structures. Here, we demonstrate the use of carboxyl- and amine-terminated self-assembled molecular layers (SAMs) to immobilize Cu at the Cu∕SiO2 interface. Amine-terminated SAMs at the Cu∕SiO2 interface increase the Cu diffusion-induced device failure time by a factor of 3 compared to interfaces without a barrier. Carboxyl-terminated SAMs obtained by grafting succinyl chloride onto the amine-terminated SAM show more than an additional factor of 4 increase in failure time. Coordination complex formation though strong interactions between COOH and Cu+ at the Cu∕SAM interface is the likely reason for the effective immobilization of Cu.