Types Of Organic Ligands Research Articles

Syntheses, Structures, and Solution Studies of Multicomponent Macrocycles and Cages Based on Versatile Ligands.

Different types of multinuclear half-sandwich rhodium macrocycles and cages were designed and synthesized by using two similar multifunctional hydroxamate ligands (pyrazine-2-hydroxamic acid (NaHL1 ) and 4,4'-bipyridine-2-hydroxamic acid (KHL2 )) featuring one monodentate site and two pairs of chelating sites. The RhIII -PdII heterometallic macrocycles were constructed by using the semi-open palladium(II) source [Pd(en)Cl2 ] with two free acceptor sites. However, only one kind of macrocycle was found when the shorter ligand L1 was used, while in for the larger ligand, various spectroscopic techniques demonstrated the coexistence of hexanuclear and octanuclear macrocycles in solution and the proportions of both components depended on concentration and temperature. The palladium salt Pd(NO3 )2 , as a source of "naked" Pd2+ , was introduced to assemble the cuboid-shaped cage composed of two types of metal ions and three types of organic ligands. In addition, two silver(I)-containing mixed-metal complexes bridged by pyrazine were obtained, in which two forms of decanuclear complex with C2v and C2h point symmetry cocrystallized-one is a polymeric structure and the other is a discrete cage. However, the third form, with D2 point symmetry, was found in the larger cage.

The influence of surface modification, coating agents and pH value of aqueous solutions on physical properties of magnetite nanoparticles investigated by ESR method

The article presents the results of electron spin resonance (ESR) studies for aqueous solutions of functionalized superparamagnetic iron(II,III) oxide nanoparticles. The samples studied differed in type of organic ligands at the magnetite surface, type of coating agent and pH value of aqueous solutions. The ESR spectra of the samples were obtained at room temperature and at 230K. The field cooling (FC) experiment was performed for selected samples, and the effective anisotropy field (HK2) and the first order magnetocrystalline anisotropy constant (K1) was calculated. The process of the nanoparticles diffusion in different environments (human blood, human serum) forced by an inhomogeneous magnetic field was monitored and their interactions with different solvents have been discussed. It has been shown that ESR method is useful to observe the impact of organic ligands at the magnetite surface, type of coating agent and pH value of aqueous solutions on the properties of iron(II,III) oxide nanoparticles.

A linear heterometallic bismuth-copper coordination polymer containing two types of organic ligands.

In the linear coordination polymer catena-poly[[[aqua(1,10-phenanthroline-κ(2)N,N')copper(II)]-μ-pyridine-2,6-dicarboxylato-κ(4)O(2):O(2'),N,O(6)-[(nitrato-κ(2)O,O')bismuth(III)]-μ-pyridine-2,6-dicarboxylato-κ(4)O(2),N,O(6):O(6')] dihydrate], {[Bi(III)Cu(II)(C7H3NO4)2(NO3)(C12H8N2)(H2O)]·2H2O}n, the Bi(III) cation is O,N,O'-chelated by the two pyridine-2,6-dicarboxylate ligands and O,O'-chelated by the nitrate anion, the nine coordinating atoms conferring a tricapped trigonal prismatic environment on the metal centre. Each pyridine-2,6-dicarboxylate ligand uses one of its carboxylate O atoms to bind to an aqua(1,10-phenanthroline)copper(II) unit, the Cu-O dative bonds giving rise to the formation of a ribbon motif. The Cu(II) cation exhibits a square-pyramidal geometry. The ribbon motif propagates along the shortest axis of the triclinic unit cell and the solvent water molecules are hydrogen bonded to the same ribbon.

Two Organic–Inorganic Hybrids Assembled by Carboxylate-Bridging Lanthanide-Substituted Polyoxometalate Dimers with Copper–ethylendiamine Cations

Two new organic–inorganic hybrid carboxylate-bridging copper–lanthanide heterometallic polyoxotungstates K2[Cu(en)2(H2O)]2{[Cu(en)2]3[Ce(GeW11O39)(H2O)2]2(C2O4)}·11H2O (1) and K2 [Cu(en)2(H2O)]2{[Cu(en)2(H2O)]2[Tb(PW11O39)(CH3COO)(H2O)]2}·15H2O (2) (en = 1,2-ethylenediamine) have been prepared under hydrothermal conditions and characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), thermogravimetric (TG) analyses and X-ray single-crystal diffraction. X-ray structural analyses reveal that 1 exhibits the 1D zigzag chain architecture formed by dimeric oxalate-bridging {[Cu(en)2]3[Ce(GeW11O39)(H2O)2]2(C2O4)}6− units and [Cu(en)2]2+ linkers whereas 2 displays a typical hybrid acetate-bridging dimeric structure [(α-PW11O39)Tb(H2O)(η2,μ-1,1)–CH3COO] 2 10− modified by [Cu(en)2(H2O)]2+ fragments. Notably, both contain 2:2-type carboxylate-bridging monolanthanide-substituted Keggin-type dimeric moieties and two types of organic ligands. 1 represents the rare 1D Cu–Ln heterometallic germanotungstate containing mixed ligands of en and oxalate whereas 2 represents the rare dimeric organic–inorganic hybrid Keggin-type phosphotungstate containing both Cu–Ln heterometals and mixed ligands of en and acetate. Two new organic–inorganic hybrid copper–lanthanide heterometallic polyoxotungstates containing mixed organic ligands of en and carboxylate were successfully separated under hydrothermal conditions. 1 exhibits the 1D zigzag chain architecture formed by dimeric oxalate-bridging {[Cu(en)2]3[Ce(GeW11O39)(H2O)2]2(C2O4)}6− units by [Cu(en)2]2+ linkers, whereas 2 displays a typical hybrid acetate-bridging dimeric structure [(α-PW11O39)Tb(H2O)(η2,μ-1,1)–CH3COO] 2 10− modified by [Cu(en)2(H2O)]2+ fragments.

A Composite Based on {VO3}n n- Chain Containing Two Different Types of Organic Ligands

A Composite Based on {VO3}n n- Chain Containing Two Different Types of Organic Ligands

Structures and magnetic properties of Mn and Co inorganic–organic frameworks with mixed linear dicarboxylate ligands

The structures and magnetic properties of two transition metal frameworks that feature a mixture of two linear dicarboxylate ligands are reported. Compounds 1, Mn2(C4H4O4)(C6H8O4)(H2O)4·2H2O, and 2, Co6(C4H4O4)4(C6H8O4)(OH)2(H2O)4·5H2O, contain a mixture of succinate and adipate ligands but adopt significantly different structures. Compound 1 features layers of MnO6 dimers, intra-connected by carboxylate groups, with neighbouring dimers connected to each other via the adipate ligands in one direction and succinate ligands in the other. Extensive hydrogen bonding in the third dimension provides the main force holding layers together. Framework 2 has inorganic layers of CoO6 octahedra arranged into rings of 14 members each, with adipate ligands providing inter-layer connectivity. The structures of these two compounds are compared to Mn and Co dicarboxylate frameworks containing only one type of organic ligand, including Co(C6H8O4), compound 3, whose structure is reported in this work for the first time; they are found to be significantly different from those that form under similar conditions. Both compounds order magnetically near 2 K. Compound 1 is an antiferromagnet, in which the intra-dimer coupling dominates the magnetic behaviour, while framework 2 is most likely a canted antiferromagnet. Both compounds undergo magnetic phase transitions with increasing applied magnetic fields, at 14 kOe and 0.35 kOe in 1 and 2, respectively. The transition in the Mn compound is a simple spin flop but in the Co compound the suppression of the long range ordered state is also accompanied by the elimination of the ferromagnetic component of its magnetic interactions.

Study of synthesis and fluorescence of europium complex/copolymer composite optical resins by in situ preparation

The in situ preparation and the photo-physical properties of optical resins containing lanthanide complexes have been investigated. Composite resins with narrow bandwidth and intense fluorescence were obtained through a free radical copolymerization of methacrylic acid (MA), styrene (St), EuCl 3·6H 2O, and organic ligands, in which the binary or ternary Eu 3+ lanthanide ion complexes were synthesized in situ by a copolymerization process. The molecular structure, the dispersed morphology of the lanthanide complexes, and the luminescence properties of the optical resins were characterized. The relationships between the fluorescence properties of the optical resins and the types of organic ligands, and the relative molar ratio between the organic ligands and the lanthanides ion were investigated. Transmission electron microscopy (TEM) results showed that the lanthanide complexes, with a mean diameter below 20 nm, were homogeneously dispersed in the optical resins. This in situ composite resin showed stronger luminescence intensity and a longer luminescence lifetime than that made by the doping method at the same concentration.

1-D, 2-D, and 3-D Organic–Inorganic Hybrids Assembled from Keggin-type Polyoxometalates and 3d-4f Heterometals

A series of organic–inorganic hybrid polyoxometalate derivatives {[Cu(en)2]1.5[Cu(en)(2,2′-bipy)(H2O)n]Ce[(α-PW11O39)2]}6– [(Ln, n) = (CeIII, 0) for 1, (PrIII, 1) for 2)], {[Cu(en)2]2(H2O)[Cu(en)(2,2′-bipy)]Ln[(α-HPW11O39)2]}4– [Ln = GdIII for 3, TbIII for 4, ErIII for 5] and {[Cu(en)2]1.5[Cu(en)(2,2′-bipy)]Nd[(α-H5PW11O39)2]}3– for 6 (2,2′-bipy =2,2′-bipyridine and en = ethylenediamine) have been successfully synthesized under hydrothermal conditions and further characterized by elemental analyses, inductively coupled plasma (ICP) analyses, X-ray powder diffraction (XRPD), IR spectra, UV spectra, electron paramagnetic resonance (EPR) spectra, thermogravimetric (TG) analyses, and single-crystal X-ray diffraction. The common features of 1–6 are that they all consist of sandwich-type [Ln(α-PW11O39)2]11– polyoxoanions as the fundamental building blocks and copper coordination cations as bridges. 1 and 2 show the 1-D zigzag chains, and 3–5 exhibit the unprecedented 2-D structures built by [Ln(α-PW11O39)2]11– polyoxoanions and [Cu(en)2]2+ and [Cu(en)(2,2′-bpy)]2+ cations, whereas 6 displays the scarce 3-D framework with a (46·64) topology. As expected, 1–6 contain two types of organic ligands. Furthermore, the photocatalysis properties of rhodamine-B (RhB) upon a 500 W Hg lamp irradiation in the presence of 1, 2, 3, 4, 5, or 6 have been examined. The photoluminescence property of 4 has been investigated.

Surface Ligand Population Controlled Oriented Attachment: A Case of CdS Nanowires

Using two types of organic ligands having similar chemical structure but different physical properties and varying their dynamic population at the surface of zinc blende seed nanocrystals, self-assembled zinc blende semicircular-shaped bent nanowires of CdS are synthesized via a colloidal synthetic approach. It is found that the hydrophobic tail interaction of long-chain ligands puts strain on these thin nanowires (< 2 nm diameter) and bend them to some extent, forming strained nanowires.

Influence of reaction parameters on the photoluminescence properties of free standing functionalized silicon nanocrystals

AbstractWhile silicon nanostructures acquire novel optical properties due to miniaturization, the stability of light emission is severely limited because of exciton trapping due to surface oxidation coming along with the formation of defects. Grafting of organic molecules on a hydrogen-terminated silicon surface via hydrosilylation provides a promising route to stabilize their surface against oxidation. In this communication, we report on the effect of surface passivation on the optical properties of freestanding silicon nanocrystals (Si-NCs). The surface functionalization of hydrogen-terminated Si-NCs with organic molecules was achieved via liquid phase hydrosilylation. We demonstrate that surface functionalization does not preserve the original emission of hydrogen-terminated Si-NCs. It is observed that the emission spectrum of green emitting hydrogen-terminated Si-NCs is red shifted after surface functionalization. We find that the direction of shift does not depend on the type of organic ligands and the reaction conditions, however, the amount of shift can be altered. The factors influencing the shift in the emission spectra of functionalized Si-NCs with respect to hydrogen-terminated samples are discussed.

New Types of Luminescent Lanthanide Squarato-Aminophosphonates

Hydrothermal reactions of lanthanide nitrates with aminodiphosphonate ligand (H2O3PCH2)2−N−CH2−C6H4−COOH, H5L1) and squaric acid afforded a series of isostructural lanthanide(III) squarato-phosphonates, namely, Ln(HL2) (Ln = La, 1; Pr, 2; Nd, 3; Eu, 4; Gd, 5; Tb, 6; Er, 7) (H4L2 = HOOC−C6H4−CH2−N(C4O3H)(CH2PO3H2)), in which a new multifunctional squarato-phosphonate ligand (H4L2) was formed by in situ condensation reaction between the two types of organic ligands. The seven-coordinated lanthanide(III) ions in these compounds are bridged by the squarato-aminophosphonate moieties of the {HL2}3− anions into a double layer. Each {HL2}3− anion acts as septadentate metal linker, bridging with seven lanthanide ions by using one carboxylate oxygen, three squarato, and three phosphonate oxygens. These double layers are further cross-linked via the coordination of the carboxylate groups into a pillared layered architecture. The Eu, Tb, and Nd compounds exhibit strong luminescence in red light, green light, and near-IR regions, respectively.

Luminescent Colloidal Dispersion of Silicon Quantum Dots from Microwave Plasma Synthesis: Exploring the Photoluminescence Behavior Across the Visible Spectrum

AbstractAiming for a more practical route to highly stable visible photoluminescence (PL) from silicon, a novel approach to produce luminescent silicon nanoparticles (Si‐NPs) is developed. Single crystalline Si‐NPs are synthesized by pyrolysis of silane (SiH4) in a microwave plasma reactor at very high production rates (0.1–10 g h−1). The emission wavelength of the Si‐NPs is controlled by etching them in a mixture of hydrofluoric acid and nitric acid. Emission across the entire visible spectrum is obtained by varying the etching time. It is observed that the air oxidation of the etched Si‐NPs profoundly affects their optical properties, and causes their emission to blue‐shift and diminish in intensity with time. Modification of the silicon surface by UV‐induced hydrosilylation also causes a shift in the spectrum. The nature of the shift (red/blue) is dependent on the emission wavelength of the etched Si‐NPs. In addition, the amount of shift depends on the type of organic ligand on the silicon surface and the UV exposure time. The surface modification of Si‐NPs with different alkenes results in highly stable PL and allows their dispersion in a variety of organic solvents. This method of producing macroscopic quantities of Si‐NPs with very high PL stability opens new avenues to applications of silicon quantum dots in optoelectronic and biological fields, and paves the way towards their commercialization.

Synthesis, crystal structure, and magnetic properties of a copper(II) octacyanotungstate(V)-based magnet containing two types of organic ligands

Cu 3[W(CN) 8] 2(pyrimidine) 2(3-cyanopyridine) 2 · 4H 2O, a cyanide-bridged copper(II) octacyanotungstate(V) with two types of organic ligands (pyrimidine and 3-cyanopyridine), is prepared. In this compound, the coordination geometry of W is an 8-coordinated bicapped trigonal prism where five CN groups of [W(CN) 8] are bridged to five Cu ions, and the remaining three CN groups are free. The coordination geometries of the three types of Cu ions (Cu1, Cu2, and Cu3) are 6-coordinated pseudo-octahedron. The cyano-bridged-Cu2–W–Cu3-layer is linked by a Cu1 pillar unit, and a cavity along the a axis, which is occupied by 3-cyanopyridine molecules and zeolitic water molecules, exists. The present compound shows ferrimagnetism with a Currie temperature of 7 K, a saturation magnetization of 2.9 μ B, and a coercive field of 7 Oe at 2 K.

Amorphous arsenic chalcogenide films modified using rare-earth complexes

The optical absorption and current–voltage characteristic of amorphous arsenic chalcogenide As2X3 (X=S, Se) films modified by rare-earth complexes with organic mixed-ligands have been studied. The following two types of complexes were used: europium dipivaloylmethanate Eu(thd)3 and lanthanide diethyldithiocarbamates Ln(ddtc)3 (Ln=Pr, Eu). It was shown that the use of rare-earth mixed-complexes with similar volatility to the chalcogenide volatility permits the deposition of amorphous films by thermal evaporation. The decrease in absorption coefficient at the Urbach’s edge after introduction of the europium dipivaloylmethanate complexes containing oxygen in arsenic selenide has been revealed. The type of organic ligands, incorporated in the amorphous matrix, determines the shape of current–voltage characteristic. The observed results have been discussed on the basis of the different rigidity of the structure of amorphous arsenic chalcogenides.

Organic copper complexes as a new class of proteasome inhibitors and apoptosis inducers in human cancer cells

Here we report that organic copper complexes can potently and selectively inhibit the chymotrypsin-like activity of the proteasome in vitro and in vivo. Several copper compounds, such as NCI-109268 and bis-8-hydroxyquinoline copper(II) [Cu(8-OHQ) 2], can inhibit the chymotrypsin-like activity of purified 20S proteasome. In human leukemia cells, proteasome inhibition occurs within 15 min after treatment, followed by apoptosis. Neither proteasome inhibition nor apoptosis occurs in non-transformed, immortalized human natural killer cells under the same treatment. Furthermore, proteasome inhibition and apoptosis induction were detected in prostate cancer cells treated with the ligand 8-OHQ alone following pre-treatment with copper(II) chloride. None of these events occurred in cells treated with copper(II) chloride alone, 8-OHQ alone (without growth in copper-enriched media), or nickel(II) chloride pre-treatment followed by 8-OHQ. Furthermore, we found that copper-mediated inhibition of purified 20S proteasome cannot be blocked by a reducing agent and that organic copper compounds do not generate hydrogen peroxide in the cells, suggesting that proteasome inhibition and apoptosis induction are not due to copper-mediated oxidative damage of proteins. Our results suggest that certain types of organic ligands could bind to tumor cellular copper, forming potent proteasome inhibitors and apoptosis inducers at copper concentrations found in tumor tissues.

Cadmium binding by fractions of dissolved organic matter and humic substances from municipal solid waste compost.

The agricultural practice of amending soils with composted municipal solid waste (MSW) adds significant amounts of organic matter and trace metals, including Cd. Under these conditions, soluble organic complexes of Cd formed in the compost may be more significant than previously thought, due to Cd bioavailability and mobility in the soil environment. To study the relative importance of different types of organic ligands in MSW compost for the binding of Cd, six fractions of the dissolved organic matter (DOM) in addition to humic acid (HA) and fulvic acid (FA) were extracted and their complexation of Cd quantified at pH 7 using an ion-selective electrode (ISE). The highest complexing capacities (CC) for Cd were found for the most humified ligands: HA (2386 micromol Cd g(-1) C of ligand), predialyzed FA (2468 micromol Cd g(-1) C), and HoA, a fulvic-type, easily soluble fraction (1042 micromol Cd g(-1) C). The differences in CC for Cd of the various organic ligands were not directly related to total acid-titratable or carboxylic groups, indicating the importance of sterical issues and other functional groups. The strength of association between Cd and the organic ligands was characterized by calculating stability constants for binding at the strongest sites (pK(int)) and modeling the distribution of binding site strengths. The pK(int) values of the DOM fractions ranged between 6.93 (HiN: polysaccharides) and 8.11 (HiB: proteins and aminosugars), compared with 10.05 for HA and 7.98 for FA. Hence, the highly complex and only partially soluble organic molecules from compost such as HA and FA demonstrated the highest capacity to sequester Cd. However, strong Cd binding of organic ligands containing N-functional groups (HiB) in addition to a high CC of soluble, humified ligands like HoA indicated the relevance of these fractions for the organic complexation of Cd in solution.

Kinetics of Iron Oxide Dissolution as Enhanced by Organic Ligands

Previous studies indicate that colloids may be released in the subsurface environment upon the dissolution of cementitious iron oxides (Ryan and Gschwend, 1992). Our field investigation showed that the concentrations of both total and ferrous iron increased during an injection of natural organic matter (NOM), implying an NOM-enhanced dissolution of iron oxide and mobilization of the oxide colloids in s i tu (Liang et al. , 1993). Because of the lack of quantitative data, predictions on the rates and the extent of iron-oxide dissolution in a natural system are hindered. The current laboratory studies are aimed at developing and testing conceptual and mathematical models for iron oxide dissolution. Here experimental work is undertaken to determine the rates of dissolution of ferrihydrite as influenced by organic ligands, such as oxalate, citrate and ascorbate ions. The type of organic ligands, ligand concentrations, and pH were varied in order to determine the effect of each variable on the kinetics of the dissolution reaction. An important application of this project is to assess iron oxide colloid mobilization corresponding to the dissolution of the oxide in groundwater, which is investigated in column flowthrough systems.

Activation of metal-bound salicylaldoximes

Neutral, bis-complexes of oxovanadium(IV) with salicylaldoximes and salicylketoximes react with a range of nitriles to afford a novel organic ligand type; the prototypical reaction product [VVO2{C6H4(O)CHN–OC(Me)NH}] is characterised by single crystal X-ray diffraction and spectroscopic studies.

Cumene hydroperoxide decomposition in the presence of metal complex catalysts supported on amorphous SiO2

By the method of molecular deposition, ions of CrO 2 2+ VO3+ and MoO 2 2+ were supported on a matrix of amorphous SiO2. Different types of organic ligands were supported subsequently on the surface compounds so formed. The catalytic activity of the samples was studied in the decomposition of comene hydroperoxide.

The reactivity of acetylenes coordinated to cobalt : III. Reaction of the butene-2-olide-4 complexes, (C 4O 2R 1)Co 2(CO) 7 with acetylenes; formation of new types of organic ligands

The “lactone” complexes, (C 4O 2R 1,R 2)Co 2(CO) 7, [μ 2-carbonyl)[μ 2-spiro-(2,3-substituted-2-butene-4-olide-4-ylidene)] [bis(tricarbonyl-cobalt)(CoCo) derivatives, were found to react with acetylenes (R 3C 2R 4. This reaction yields the known acetylene complexes (R 3C 2R 4Co 2(CO) 6 and two isomeric compounds with the composition [(C 4O 2R 1,R 2)(R 3C 2R 4) 2]Co 2(CO) 5. Spectroscopic arguments and X-ray structure determination show that both isomers contain σ, π-C 5 ligands bonded to both Co atoms. The structures of these isomerswere identified.