Reactivity of surface complexes in the selective catalytic reduction of NO x on supported heteropoly compounds

The reactivity of surface complexes in the selective catalytic reduction of NO _x on supported heteropoly compounds has been investigated by in situ IR spectroscopy. The best performance is shown by CeO₂-supported catalysts. The conversion rate of the intermediate nitrate complexes obeys a zeroth-order equation, like the formation rate of the propylene activation products, namely, surface acetate and formate complexes. The conversion rate of the surface nitrate complexes is determined by the propylene oxidation selectivity, which, in turn, is related to the composition of the heteropoly compound. Among the heteropoly compounds examined, the most appropriate ones are those in which vanadium ions are in both anionic and cationic positions. These pair sites serve to activate propylene, and the activation product reacts efficiently with the nitrate complexes.     

A spectroscopic study of the iodine complexes of donors—pyridines,phenanthrolines, bipyridines and diazines

Ultraviolet—visible spectral data of iodine complexes of n- and π-donors have been interpreted by considering that the repulsion energy responsible for the blue shift of the iodine band is also experienced by the donor partner which causes the blue shift of the original band of the donor. This reasoning explains the spectral data of iodine complexes of benzene, pyridine-N-oxide and stilbazoles. Ultraviolet—vis. spectra of the iodine complexes of pyridine, aminopyridines and diazines have been reinvestigated and discussed in the light of the above reasoning. The above reasoning is extended to the CT spectra of iodine complexes of twin-site donors such as 1,10-phenanthroline, its methyl and chloro derivatives, 1,7 and 4,7-phenanthrolines, 2,2′-bipyridine and 4,4′-bipyridine. Arguments are presented which indicate that the donors used in this study form only 1:1 complexes with iodine. The thermodynamic parameters were evaluated for iodine complexes of the above twin-site donors. The kinetics of transformation of outer CT complexes between the donors and iodine to inner complexes is presented and discussed. Two CT bands are observed for the iodine complexes of 1,10-phenanthroline and its substituents. These bands are explained by assuming a structure for the 1,10-phenanthroline complex in which iodine is in dynamic equilibrium between the two nitrogens.     

Cyclic voltammetric studies of copper(II) dipeptide complexes. Evidence for copper(I) dipeptide complexes in aqueous media

The reduction of the title complexes was studied by cyclic voltammetry in aqueous media. It proceeds through a one-electron process generating intermediate copper(I) dipeptide complexes. The copper(I) dipeptide complexes are found to be short-lived and undergo transformations eventually generating Cu⁰ at the mercury electrode. The unchanged fraction of the copper(I) species is re-oxidised to the copper(II) complexes. The Cu⁰ generated undergoes a two-electron oxidation at a more anodic potential than the copper(I) complexes. pH-dependence of the title complexes is also investigated by cyclic voltammetry.     

Computational study of the interaction of indole-like molecules with water and hydrogen sulfide

The characteristics of the interaction between water and hydrogen sulfide with indole and a series of analogs obtained by substituting the NH group of indole by different heteroatoms have been studied by means of ab initio calculations. In all cases, minima were found corresponding to structures where water and hydrogen sulfide interact by means of X-H···π contacts. The interaction energies for all these π complexes are quite similar, spanning from -13.5 to -18.8 kJ/mol, and exhibiting the stability sequence NH > CH(2) ≈ PH > Se ≈ S > O, for both water and hydrogen sulfide. Though interaction energies are similar, hydrogen sulfide complexes are slightly favored over their water counterparts when interacting with the π cloud. σ-Type complexes were also considered for the systems studied, but only in the case of water complexes this kind of complexes is relevant. Only for complexes formed by water and indole, a significantly more stable σ-type complex was found with an interaction energy amounting to -23.6 kJ/mol. Oxygen and phosphorous derivatives also form σ-type complexes of similar stability as that observed for π ones. Despite the similar interaction energies exhibited by complexes with water and hydrogen sulfide, the nature of the interaction is very different. For π complexes with water the main contributions to the interaction energy are electrostatic and dispersive contributing with similar amounts, though slightly more from electrostatics. On the contrary, in hydrogen sulfide complexes dispersion is by far the main stabilizing contribution. For the σ-type complexes, the interaction is clearly dominated by the electrostatic contribution, especially in the indole-water complex.     

基于四齿配体的蓝光d8金属配合物及其OLED应用的研究进展

用于有机发光二极管(OLED)的红光和绿光磷光金属配合物材料在稳定性和发光效率方面均已达到了目前产业化应用的要求,而蓝光磷光配合物则在稳定性方面无法达到应用条件。高能量的激发态以及d-d态引起的配合物分解是造成蓝光磷光OLED器件稳定性差的原因之一。采用四齿配体开发d~8金属配合物是同时提升配合物发光效率和稳定性的途径之一,有望在蓝光磷光材料和器件应用方面取得突破。本文总结了基于四齿配体的蓝光铂(Ⅱ)和钯(Ⅱ)配合物的研究进展,通过探讨配体结构对配合物光物理性质和稳定性的影响,为继续开发具有应用前景的蓝光金属配合物材料提供了指导性方向。     

Zur reaktivität komplexgebundener carbocyclen: XV. Neue wege zu indenyl-diolefen-komplexen von cobalt und rhodium

The formation of (indenyl)rhodium(diolefin) complexes is described, using bis(indenyl) magnesium. On protonation of these complexes an η⁵-η⁶ shift of the indenyl ligand is observed. The corresponding cobalt complexes are obtained by lithium reduction of bis(indenyl)cobalt in the presence of the diolefin. The bidentate ligand 1,5-cyclooctadiene is readily replaced in these complexes by carbon monoxide. All compounds were characterised by ¹³C NMR spectroscopy.     

Switching from Metal- to Ligand-Based Oxidation in Cobalt Complexes with Redox-Active Bisguanidine Ligands

The control of the redox reactivity, magnetic and optical properties of the different redox states of complexes with redox-active ligands permits their rational use in catalysis and materials science. The redox-chemistry of octahedrally coordinated high-spin Co^II complexes (three unpaired electrons) with one redox-active bisguanidine ligand and two acetylacetonato (acac) co-ligands is completely changed by replacing the acac by hexafluoro-acetylacetonato (hfacac) co-ligands. The first one-electron oxidation is metal-centered in the case of the complexes with acac co-ligands, giving diamagnetic Co^III complexes. By contrast, in the case of the less Lewis-basic hfacac co-ligands, the first one-electron oxidation becomes ligand-centered, leading to high-spin Co^II complexes with a radical monocationic guanidine ligand unit (four unpaired electrons). Ferromagnetic coupling between the spins on the metal and the organic radical in solution is evidenced by temperature-dependent paramagnetic NMR studies, allowing to estimate the isotropic exchange coupling constant in solution. Second one-electron oxidation leads to high-spin Co^II complexes with dicationic guanidine ligand units (three unpaired electrons) in the presence of hfacac co-ligands, but to low-spin Co^III complexes with radical monocationic, peralkylated guanidine ligand (one unpaired electron) in the presence of acac co-ligands. The analysis of the electronic structures is complemented by quantum-chemical calculations on the spin density distributions and relative energies of the possible redox isomers.     

New dioxygen-inert triphenylantimony(v) catecholate complexes based on <Emphasis Type="Italic">o</Emphasis>-quinones with electron-withdrawing groups

New triphenylantimony(v) catecholate complexes were synthesized by oxidative addition of sterically hindered o-benzoquinones containing electron-withdrawing substituents in different positions of the carbon ring to triphenylantimony. The complexes were characterized using IR spectroscopy, NMR spectroscopy, and cyclic voltammetry. The oxygen-inertness of the complexes is shown by NMR spectroscopy and electrochemical studies. The introduction of electron-withdrawing substituents to the catecholate ligand shifts the first oxidation potential of the complexes to the electropositive region and thus deactivates the triphenylantimony(v) catecholate complexes in the reaction with molecular oxygen.     

Synthesis,characterization, semi-empirical study,and biological activities of organotin(IV) complexes with cyclohexylcarbamodithioic acid as biological active ligand

Cyclohexylcarbamodithioic acid has been synthesized by the reaction of cyclohexylamine with carbon disulfide at room temperature. Its complexes have been synthesized by the reaction of cyclohexylcarbamodithioic acid with organotin(IV) chlorides in 1?:?1/1?:?2 molar ratio. The ligand and complexes have been characterized by elemental analysis, infrared (IR), and multinuclear (¹H, ¹³C, and ¹¹⁹Sn) NMR spectroscopy. Elemental data show good agreement between calculated and found values of carbon, hydrogen, nitrogen, and sulfur. IR data show that the ligand is bidentate and complexes exhibit a five-coordinate geometry in the solid state, which is also confirmed by semi-empirical studies. NMR data show that the complexes exhibit tetrahedral geometry in solution state. The ligand and its complexes were screened for their in vitro mutagenic, antimicrobial, MIC, antioxidant activities, and cytotoxicity. Biological screening data demonstrate that complexes show significant activity against various bacterial and fungal strains and are good antioxidants. The cytotoxicity data show positive lethality for complexes as compared to ligand and can play a very significant role in drug development.     

Tertiary-poly-amine ligands as stabilisers of transition metal complexes with uncommon oxidation states

Abstract

Tertiary-amine ligands are known to be poorer [sgrave] donor ligands than the corresponding primary- or secondary-amine ligands. They are known to shift the redox potentials of given couples to the anodic direction relative to the corresponding complexes with primary- or secondary-amine ligands. A review of data in the literature and of recent results on nickel complexes with tetra-aza-macrocyclic ligands and copper complexes with open chain polyamine ligands suggests that the major source for these effects is the poorer solvation of the complexes with the tertiary-amine complexes due to the lack of hydrogen bonding between the complexes and the solvent, or the counter ions. Thus the stabilisation of low valent transition metal complexes by tertiary-amine ligands is due to thermodynamic reasons. On the other hand, tertiary-amine-macrocyclic ligands stabilise high valent complexes because the route to the formation of imine groups is kinetically inhibited in these complexes.     

Primary Photoprocesses in Thionine in Supramolecular Complexes with Cucurbit[7,8]urils in Water

Thionine (ThH⁺) molecules form monomeric ThH⁺@CB7 (1: 1) and dimeric 2ThH⁺@CB8 (2: 1) complexes with cucurbit[7,8]urils (CB7) and (CB8) in water. Unlike the case free ThH⁺ molecules, the absorption spectrum of the complexes is characterized by a hypsochromic shift of the maximum by 6 and 41 nm for ThH⁺@CB7 and 2ThH⁺@CB8, respectively. The ThH⁺@CB7 complexes exhibit fluorescence, unlike the nonfluorescing 2ThH⁺@CB8 complexes. The monomeric complexes undergo intersystem crossing to the triplet state with a lifetime of 14 μs. The dimeric complexes have a very low quantum yield of the triplet state. The triplet state of the dimeric complexes was populated by photosensitized excitation by triplet–triplet energy transfer. The lifetime of the triplet state is ≈50 μs.     

Stability of nonplanar N-methylporphyrins and their zinc complexes

Resistance of N-methyl-substituted porphyrins and their Zn(II) complexes to thermooxidative degradation and to the action of a DMSO-AcOH proton-donor solvent was studied by thermogravimetry and chemical kinetics. The fairly low stability of the complexes is caused by decreased planarity and, as a consequence, aromaticity of the macrorings and also by the tendency of the complexes to demethylation. The stability of the zinc complexes in AcOH varies in parallel with the degree of nonplanarity and resistance to thermooxidative degradation of their ligands.     

Syntheses,characterizations and bioactivities on HeLa cells and KB cells of two dinuclear manganese complexes with carboxylate bridges

To explore anti-tumor activities of manganese complexes, two complexes have been synthesized and characterized. Complex 1 is bridged by 1,10-phenanthroline and 2,4-biphenyl dicarboxylate. The two complexes have strong fluorescent emission and interact with DNA in an intercalative mode. The complexes also exhibit significant cytotoxic specificity and cancer cell inhibition.     

Speciation of Charged Complexes by Donnan Dialysis

Abstract

The assignment of metal complexes to various regimes on the basis of their dissociation kinetics is one type of metal speciation study. The most common scheme, which involves column ion-exchange as a means of separating free metal ions and metals in the form of highly labile complexes from other forms of metals in the sample, is demonstrated to categorize incorrectly stable, charged complexes such as iron(II) and nickel(II) o-phenanthroline as labile. Donnan dialysis is an alternative ion-exchange method for metal speciation studies. Data are provided which demonstrate that the above complexes are correctly assigned by the Donnan dialysis method. The relative labilities of ethylenediamine and triethylenetetramine complexes of iron (II) and nickel (II) are also correctly determined by Donnan dialysis.     

Self-Assembly and Ordering of Peptide-Based Cavitands in Water and DMSO: The Power of Hydrophobic Effects Combined with Neutral Hydrogen Bonds

Directional self-assembly of uncharged molecules in water is a major challenge in supramolecular chemistry. Herein, it is demonstrated that peptide-based cavitands wrap around a hydrophobic core (fullerene C₆₀) by a combination of the hydrophobic effect and hydrogen-bonding interactions to form highly ordered three-component complexes in water that resemble the molten-globule stage of protein folding. The complexes were characterized by DOSY NMR spectroscopy, small-angle X-ray scattering, and circular dichroism, and their structures were confirmed by X-ray crystallography. Enhancement of the CD signals by nearly one order of magnitude and increased hydrolytic stability of hydrazone bonds of the complexes relative to the nonassembled species were observed. In contrast, DMSO and DMSO/water mixtures were found to be highly disintegrative for these complexes. Interestingly, some cavitands can only be synthesized in the presence of the hydrophobic template followed by disassembly of the complexes.     

Structural and thermal decomposition characteristics of mixed-ligand complexes of Cu(II), Ni(II), Co(II) and Zn(II)

Mixed-ligand complexes of Cu(II), Ni(II), Co(II) and Zn(II) with 8-hydroxyquinoline and thiophene-2-carboxylic acid as two different ligands, have been isolated in pure state. The formation of these complexes has been inferred potentiometrically. The isolated complexes have been characterized by their elemental analyses, IR and electronic spectra, conductivity and magnetic measurements. Solid state dehydration of the hydrated complexes and subsequent decomposition of the anhydrous complexes have been studied by simultaneous DTA and TG techniques. The thermal stability order of the hydrated compounds is Cu>Co>Ni>Zn, but in the decomposition process the trend observed is Co>Zn>Ni>Cu. Some parameters like activation energy and order of reaction for each process have been computed.     

Syntheses,structures, and properties of Ni(II) complexes with 5,5′-bis(4-halogenphenyl)diazo-dipyrromethane

Ni(II) complexes with 5,5′-bis(4-halogenphenyl)diazo-dipyrromethane have been synthesized and characterized by X-ray crystallography. All the complexes have similar crystal structures in which Ni(II) is square-planar by coordinating to two pyrrole and two azo nitrogen atoms. The azo-pyrroles of the ligands can be converted to the hydrazone tautomer after complexing nickel. Moreover, the C–H?···?Ni interaction played an important role in directing self-assembly of the complexes. The UV-Vis spectra of the complexes showed great difference with the metal complexes of pyrrol-2-imine.     

Study of diketone/metal ion complexes by electrospray ionization mass spectrometry: Influence of Keto-Enol tautomerism and chelation

The formation and collisionally activated dissociation (CAD) behavior of a series of complexes containing cyclic or linear diketone ligands and alkali, alkaline earth, or transition metal ions are investigated. Electrospray ionization (ESI) is utilized for introduction of the metal ion complexes into a quadrupole ion trap mass spectrometer. The proximity of the carbonyl groups is crucial for formation and detection of ion complexes by ESI. For example, no metal ion complexes are observed for 1,4-cyclohexanedione, but they are readily detected for the isomers, 1,2-and 1,3-cyclohexanedione. Although the diketones form stable doubly charged complexes, the formation of singly charged alkaline earth complexes of the type (nL + M²⁺ ? H⁺)⁺ where L = 1,3-cyclohexanedione or 2,4-pentanedione is the first evidence of charge reduction. CAD investigations provide further evidence of charge reduction processes occurring in the gas-phase complexes. The CAD studies indicate that an intramolecular proton transfer between two diketone ligands attached to a doubly charged metal ion, followed by elimination of the resulting protonated ligand, produces the charge reduced complex. For transition metal complexation, the preference for formation of doubly charged versus singly charged complexes correlates with the keto-enol distribution of the diketones in solution.     

富勒烯系列配合物η2-C60[Ru(NO)(PPh3)]n的合成与光电性能

合成了一系列新的富勒烯钌配合物.通过元素分析、紫外-可见光谱、红外光谱、光电子能谱(XPS)和13C及31PNMR等多种手段对它们进行了表征.结果表明.该系列配合物分子内存在超共轭效应,共轭电子多.离域性好.通过光伏效应装置研究了它们的光电性能,结果显示该系列配合物具有良好的光电性能.     

Complex Formation Reactions of Promethazine Copper(II) and Various Biologically Relevant Ligands. Synthesis,Equilibrium Constants,Spectroscopic Characterization and Biological Activity

Binary and ternary complexes of copper(II) involving promethazine, N,N-dimethyl-3-(phenothiazin-10-yl)propylamine (Prom) and various biologically relevant ligands containing different functional groups, were investigated. The ligands (L) are dicarboxylic acids, amino acids, amides and DNA constituents. The ternary complexes of amino acids, dicarboxylic acids or amides are formed by simultaneous reactions. The results showed the formation of Cu(Prom)(L) complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. Amides form both Cu(Prom)(L) complexes and the corresponding deprotonated species Cu(Prom)(LH₋₁). The ternary complexes of copper(II) with (Prom) and DNA are formed in a stepwise process, whereby binding of copper(II) to (Prom) is followed by ligation of the DNA components. DNA constituents form both 1:1 and 1:2 complexes with Cu(Prom)²⁺. The stability of these ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters Δlog₁₀ K. The values of Δlog₁₀ K indicate that the ternary complexes containing aromatic amino acids were significantly more stable than the complexes containing alkyl- and hydroxyalkyl-substituted amino acids. The concentration distribution of various complex species formed in solution was also evaluated as a function of pH. The solid complexes [Cu(Prom)L)] where L=1,1-cyclobutanedicarboxylic acid (CBDCA), oxalic and malonic acid were isolated and characterized by elemental analysis, infrared, TGA, and magnetic susceptibility measurements. Spectroscopic studies of the complexes revealed that the complexes exhibits square planar coordination with copper(II). The isolated solid complexes have been screened for their antimicrobial activities using the disc diffusion method against some selected bacteria and fungi. The activity data show that the metal complexes are found to have antibacterial and antifungal activity.