Ru(II) and Zn(II) complexes of multicomponent ligands incorporating triazine-based tridentate ligands

Ru(II) and Zn(II) complexes of multicomponent ligands have been synthesised and characterised incorporating triazine-based coordinating motifs with pendant phenanthryl and phenyl–phenanthryl groups. At room temperature the ligands emit from intra-ligand charge-transfer (ILCT) states, the energy of which may be lowered significantly by metal–ion coordination (e.g. Zn(II)). The ILCT state is efficiently quenched in the Ru(II) complexes by energy transfer to a low-lying metal–ligand charge-transfer ³MLCT state.     

Antibacterial Co(II) and Ni(II) Complexes of N-(2-Furanylmethylene)-2-Aminothiadiazole and Role of SO(4), NO(3), C(2)O(4) and CH(3)CO(2) anions on Biological Properties

Co(II) and Ni(II) complexes with a Schiff base, N-(2-furanylmethylene)-2-aminothiadiazole have been prepared and characterized by their physical, spectral and analytical data. The synthesized Schiff-bases act as tridentate ligands during the complexation reaction with Co(II) and Ni(II. metal ions. They possess the composition [M(L)(2)]X(n) (where M=Co(II) or Ni(II), L=, X=NO(3) (-), SO(4) (2-), C(2)O(4) (2-) or CH(3)CO(2) (-) and n=1 or 2) and show an octahedral geometry. In order to evaluate the effect of anions upon chelation, the Schiff-base and its complexes have been screened for antibacterial activity against bacterial strains e.g., Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.     

Biologically Active Co(II) and Ni(II) Complexes of N-(2-Thienylmethylene)-2-Aminothiadiazole

Co(II) and Ni(II) complexes Schiff base, N-(2-thienylmethylene)-2-aminothiadiazole have been prepared and characterized by their physical, spectral and analytical data. The title Schiff-base acts as NNS donor tridentate during the complexation reaction with these metal ions having a composition, [M(L)(2)]X(n) where M=Co(II) or Ni(II), L=, X=NO(3) (-), SO(4) (2-), C(2)O(4) (2-) or CH(3)CO(2) (-) and n=1 or 2 and show an octahedral geometry. In order to evaluate the effect anions upon chelation, the Schiff-base and its new complexes have been screened for their antibacterial activity against bacterial strains e.g., Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.     

Study of multicomponent complexes between polycarboxylic acid,transition metal ions and non-ionic polymers

Multicompoent complexes of a typical polyelectrolyte like poly(acrylic acid) (PAA) have been prepared by incorporating transition metal ions (e. g. Cu(ll) and Ni(ll)) and non-ionic polymers (e. g. PVP, PEO) in the polyelectrolyte chain in a definite sequence. The formation of these complexes has been studied by several techniques, such as viscometry, potentiometry, conductometry, and IR spectroscopy. A scheme is suggested to explain the mode of formation of such complexes.     

Synthesis, Characterization and Biological Properties of Tridentate NNO, NNS and NNN Donor Thiazole-Derived Furanyl, Thiophenyl and Pyrrolyl Schiff Bases and Their Co(II), Cu(II), Ni(II) and Zn(II) Metal Chelates

2-Aminothiazole undergoes condensation reactions with furane-, thiophene- and pyrrole-2-carboxylaldehyde to give tridentate NNO, NNS and NNN Schiff bases respectively. These tridentate Schiff bases formed complexes of the type [M (L)(2)]X(2) where [M=Co(II), Cu(II), Ni(II) or Zn(II), L=N-(2-furanylmethylene)-2-aminothiazole (L(1)), N-(2-thiophenylmethylene)-2-aminothiazole (L(2), N-(2-pyrrolylmethylene)-2-aminothiazole (L(3)) and X=Cl. The structures of these Schiff bases and of their complexes have been determined on the basis of their physical, analytical and spectral data. The screening results of these compounds indicated them to possess excellent antibacterial activity against tested pathogenic bacterial organisms e.g., Escherichia coli, Staphylococcus aureous and Pseudomonas aeruginosa. However, in comparison, their metal chelates have been shown to possess more antibacterial activity than the uncomplexed Schiff bases.     

SEARCH FOH OPTIMUM CONDITIONS OF EXTRACTION OF METAL COMPLEXES WITH ALKYLIMIDAZOLES. III. STRUCTURE - EXTRACTABILITY RELATIONSHIPS FOR 1,4-DIMETHYLIMIDAZOLE COMPLEXES OF Co(II), Ni(II), Cu(II), Zn(II), AND Cd(II)

Stability constants of the 1,4-dimethylimidazole complexes of Co(II),Ni{II),Cu(II),Zn(II), and Cd(II) have been determined in aqueous solution and their structure has been elucidated. Conformational equilibria of the type octahedron-tetrahedron have been found in the case of the Co(II) and Sn(II) complexes. The extraction of all complexes has been shown to be dependent on their'molar contributions, d?n? expressed in per cent. The distribution constants have determined for each complex and the composition of the species extracted with organic solvent has been suggested.The measurements were run at 298?K, at the ionic strength of the aqueous phase of 0.5 maintained by means of KNO?3?.     

Study of CU(II)-methacrylic acid — methacrylamide copolymer interactions and formation of metal-copolymer complexes

The methacrylic acid-methacrylamide copolymer has been synthesized and characterized by known methods. The interaction of the copolymer with a typical transition metal ion (e.g. Cu²⁺) has been studied by several experimental techniques, e.g. viscometry, potentiometry, conductometry, IR, and UV spectrophotometry. Formation of metal-copolymer complexes of distinct stoichiometries have been predicted, and some schemes of complexation have been suggested to explain the mode of interaction between the components.     

Investigations of polyelectrolyte-transition metal ion association in mixed solvents

Summary Association between a typical polyelectrolyte, e.g. poly-(acrylic acid), and a divalent metal ion (e.g. Cu(II)) has been studied using different water-methanol mixtures. Preferential solvation coefficients (/c) have been calculated for various solvent compositions. Excellent agreement has been observed between minimum (/c), lowest [] and reduced viscosity (sp/c) of the complexes at a specific composition of the solvent. Interpretations have been sought in terms of polyelectrolyte conformational change at this solvent composition.     

Cationic Ruthenium‐Cyclopentadienyl‐Diphosphine Complexes as Catalysts for the Allylation of Phenols with Allyl Alcohol; Relation between Structure and Catalytic Performance in O‐ vs. C‐Allylation

A new catalytic method has been investigated to obtain either O‐ or C‐allylated phenolic products using allyl alcohol or diallyl ether as the allyl donor. With the use of new cationic ruthenium(II) complexes as catalyst, both reactions can be performed with good selectivity. Active cationic Ru(II) complexes, having cyclopentadienyl and bidentate phosphine ligands are generated from the corresponding Ru(II) chloride complexes with a silver salt. The structures of three novel (diphosphine)Ru(II)CpCl catalyst precursor complexes are reported. It appears that the structure of the bidentate ligand has a major influence on catalytic activity as well as chemoselectivity. In addition, a strong cocatalytic effect of small amounts of acid is revealed. Model experiments are described that have been used to build a reaction network that explains the origin and evolution in time of both O‐allylated and C‐allylated phenolic products. Some mechanistic implications of the observed structure vs. performance relation of the [(diphosphine)RuCp]⁺ complexes and the cocatalytic role of added protons are discussed.     

Synthesis,characterization and antitumour studies of metal chelates of N1-isonicotinoyl-3-methyl-4-(p-hydroxybenzilidene)-2-pyrazolin-5-one

The cobalt(II), nickel(II) and copper(II) complexes of N-Isonicotinoyl-3-methyl-4-(p-hydroxybenzilidene)-2-pyrazolin-5-one (IMHBP) with different counter anions have been prepared and characterized. An octahedral geometry has been assigned to the cobalt(II) and nickel(II) complexes and a square-planar structure to the copper(II) complexes. IMHBP acts as a neutral bidentate ligand in all these complexes by coordinating through the oxygen atoms of the amide group and carbonyl at position-5. The other coordination sites are satisfied by anions alone or anions and water molecules. The ligand and the complexes were screened for their possible antitumour activity. The copper(II) complexes are appreciably active in reducing mice tumours.     

Synthesis, Spectral Characterization and Biocidal Activity of Thermally Stable Polymeric Schiff Base and Its Polymer Metal Complexes

The polymer metal complexes of transition metal ions Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with a new polymeric Schiff base containing formaldehyde and piperazine moieties have been synthesized by the condensation and characterized by elemental analyses, infrared spectra, electronic spectra, magnetic susceptibility measurements and thermogravimetric analyses (TGA). The results of the electronic spectra and magnetic moments indicate that the polymer–metal complexes of Mn(II), Co(II) and Ni(II) have octahedral geometry, while the complexes of Cu(II) and Zn(II) show square planar and tetrahedral geometry, respectively. The analyses of the thermal curves of all the polymer metal complexes show better thermal stability than the polymeric Schiff base. All compounds show excellent antibacterial as well as antifungal activity against three types of bacteria and two types of fungi. The antimicrobial activities were determined by using the agar well diffusion method with 100 μg/mL concentrations of polymer metal complex.     

Carbonic Anhydrase Inhibitors Part 72 Synthesis and Antiglaucoma Properties of Metal Complexes of p-Fluorobenzolamide

Metal complexes of a heterocyclic sulfonamides possessing very strong carbonic anhydrase (CA) inhibitory properties, i.e., 5-(p-fluorobenzenesulfonylamido)-1,3,4-thiadiazole-2-sulfonamide (p-fluorobenzolamide) were prepared. The new complexes contained metal ions such as Zn(II), Cu(II), Co(II), Ni(II), Cd(II) and Mn(II). The new compounds were characterized by standard physico-chemical procedures, and assayed as inhibitors of three CA isozymes, CA I, II and IV. Very good inhibition has been evidenced both for the parent sulfonamides as well as for the prepared complexes, against all three investigated isozymes. Some of these new complexes as well as the parent sulfonamide, strongly lowered intraocular pressure (IOP) in normotensive rabbits when administered as a 2% solution into the eye.     

A different 'spin' on rhenium chemistry. synthetic approaches and perspectives of 17-electron rhenium complexes

Transition metal complexes of rhenium and technetium find wide application in nuclear medicine and the chemistry of these elements is still the focus of intense research efforts. For therapeutic and diagnostic applications, currently much attention is dedicated to the development of new targeting strategies aimed at appending the metal complexes to biological vectors (e.g. a peptide) for a site-specific delivery of the radionuclides. Advancements in radiopharmacy, however, will not only arise from the development of new targeted strategies but also from the exploration of the chemistry of these elements in their unusual oxidation states. In this respect the even number oxidation states of Re and Tc (i.e. +II, +IV and +VI) are relatively poorly understood. In particular, stable and substitutionally labile mononuclear 17-electron species of the elements (+II, d(5)) are a rarely encountered class of complexes. In this review we present our recent developments in the field of rhenium (II) chemistry with emphasis on the novel synthetic strategies we have recently introduced. We will also describe how the unique chemical and electronic properties of Re(II)-based complexes may provide a potentially new approach for applications in inorganic medicinal chemistry.     

Search for Optimum Conditions of Extraction of Transition Metal Complexes with Alkylimidazoles. I. Extraction of the Co(II), Ni(II), and Zn(II) Complexes of 1-Methylimidazole and of the Co(II) and Zn(II) Complexes of 2-Methylimidazole

Abstract

It has been shown that for the Co(II), Zn(II), and Ni(II) complexes of 1-methylimidazole and for the Co(II) and Zn(II) complexes of 2-methylimidazole, the partition coefficient D between the aqueous and organic phases is proportional to the degree of formation α _n of a definite complex. Tetrahedral species have been found to be extracted with the Co(II) and Zn(II) complexes of 2-methylimidazole and with the Zn(II) complexes of 1-methylimidazole.     

Tetrachloridocuprates(II)-Synthesis and Electron Paramagnetic Resonance (EPR) Spectroscopy

Ionic liquids (ILs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., synthesis of particles, magnetic or thermochromic materials. We present the synthesis and the results of electron paramagnetic resonance (EPR) spectroscopic analyses of a series of some new potential ionic liquids based on tetrachloridocuprates(II), [CuCl(4)](2-), with different sterically demanding cations: hexadecyltrimethylammonium 1, tetradecyltrimethylammonium 2, tetrabutylammonium 3 and benzyltriethylammonium 4. The cations in the new compounds were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. The EPR hyperfine structure was not resolved. This is due to the exchange broadening, resulting from still incomplete separation of the paramagnetic Cu(II) centers. Nevertheless, the principal values of the electron Zeemann tensor (g(║) and g(┴)) of the complexes could be determined. Even though the solid substances show slightly different colors, the UV/Vis spectra are nearly identical, indicating structural changes of the tetrachloridocuprate moieties between solid state and solution. The complexes have a promising potential e.g., as high temperature ionic liquids, as precursors for the formation of copper chloride particles or as catalytic paramagnetic ionic liquids.     

Influence of the metal centers of 2,6‐bis(imino)pyridyl transition metal complexes on ethylene polymerization/ oligomerization catalytic activities

Much work on bis(imino)pyridyl complexes with Fe(II) and Co(II) as ethylene polymerization catalysts has been reported in terms of designing new analogous ligands, while little work has been dedicated to the study of the effect of the metal center on catalyst performance. A series of bis(imino)pyridyl‐MCl₂ (M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II)) transition metal complexes were synthesized, for which single crystals of the Co(II) and Cu(II) complexes were obtained. The crystal structures indicated that these complexes had similar coordination geometries. Being applied to ethylene polymerization at 25 °C and employing 500 equiv. of methylaluminoxane as co‐catalyst, the complexes with Fe(II), Co(II) and Ni(II) centers showed, respectively, catalytic activities of 1.25 × 10⁶ g (mol Fe)^?1 h^?1 Pa for ethylene polymerization, and 3.98 × 10⁵ g (mol Co)^?1 h^?1 Pa and 5.13 × 10³ g (mol Ni)^?1 h^?1 Pa for ethylene oligomerization. In contrast, the complexes with Cu(II) and Zn(II) centers were inactive. Crystal structure data showed that the coordination interactions provided a comparatively reliable quantification of the selectivity of the bis(imino)pyridyl ligand for the studied metal ions, which was in reasonable agreement with the Irving–Williams list. Moreover, for the Ni(II) and Cu(II) complexes, the strong coordination bonds and small N(imino)? M? N(imino) angles were unfavorable for several steps in the mechanism, such as ethylene coordination to the metal center, ethylene migratory insertion and olefin chain growth. All of these will reduce the speed of the overall reaction, indicating a decrease of catalytic efficiency in a given period. The poor activity of the Zn(II) complex for ethylene polymerization may be related to the reduction process by the alkylating agent. Copyright © 2010 Society of Chemical Industry     

Synthetic, biochemical, antifertility and antiinflammatory aspects of manganese and iron complexes

Manganese(II) and iron(II) macrocyclic complexes of polyamide groups have been synthesized by the template codensation of diamines (2,6 diaminopyridine, 1,2 phenylenediamine and 1,3 phenylenediame) and triamine (diethylenetriamine) with phthalic acid in 1:2:2 molar ratios. On the basis of elemental analysis, IR, electronic, magnetic moment, M?ssbauer, mass and X-ray spectral studies, octahedral structure has been assigned to [M(N4macn)Cl2] (M = Mn(II) and Fe(II), n = 1 to 4) complexes. The complexes have been screened in vitro against a number of fungi and bacteria to assess their growth inhibiting potential. An attempt has been made to correlate the structural aspects of the compounds with their antiinflammatory and antifertility activities.     

Study of polymer-polymer complex formation involving phenolic copolymer,non-ionic polymers,and polyelectrolytes

Multicomponent interpolymer complexes have been prepared by interacting a phenolic copolymer of known composition with several non-ionic homopolymers, e.g., PVP, PEO, PVA and polyelectrolytes, such as PAA and PEI. The formation of these complexes has been studied by several techniques, such as viscometry, potentiometry, conductometry, and IR spectra. A scheme has been presented to explain the mode of interaction of the various component polymers.     

A New Class of Luminescent Platinum(II) Complexes of 1,3-Bis(N-alkylbenzimidazol-2′-yl)benzene-Type Ligands and Their Application Studies in the Fabrication of Solution-Processable Organic Light-Emitting Devices

A novel class of luminescent platinum(II) bzimb (1,3-bis(N-alkylbenzimidazol-2′-yl)benzene) complexes has been designed and synthesized. With the incorporation of various substituents on the anionic phenyl ring of the bzimb ligand, the emission color can be readily tuned. Their photophysical, electrochemical and electroluminescence properties have been studied. These platinum(II) bzimb complexes have been demonstrated to be capable of serving as phosphorescent dopants. Efficient solution-processable OLEDs (organic light-emitting devices), with a maximum external quantum efficiency of up to 4.85 %, can be achieved. This class of platinum(II) bzimb complexes represents a promising class of phosphorescent dopants for solution-processable OLEDs.     

Polymers containing metal chelate units. I. Immobilized mono- and binuclear chelates of nickel(II) and cobalt(II)

A number of polymer carriers with chelating groups such as diketones, diacylamines, and enaminoketones has been synthesized. The immobilized mono- and binuclear chelates have been prepared by the interaction of these polymeric ligands with nickel(II) and cobalt(II) acetates in alcohol. Spectral and magnetic data confirm the tetrahedral structure of the cobalt complexes and octahedral structure of the nickel complexes. The catalytic properties of the immobilized complexes in ethylene dimerization and butadiene polymerization have been investigated.