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From the apocalyptic era of antibiotic resistance, the scientific community around the world is engaged in designing and developing metal-based compounds to inhibit and control continuously rising microbial infections. Metal based triazole-derived compounds are being explored for antimicrobial actions and potentially applicable to provide effective and nontoxic drug candidates having preferred and improved pharmacological activity. Updating the existing literature supporting such details, this review combines the chemistry, synthetic aspects of formation of triazole Schiff bases, mechanism of bioactivity of metal complexes accompanied by the assessment of the biological efficacy including antibacterial, antifungal, enzyme inhibition and antioxidant activity. This review covers bioactive symmetrical and assymmetrical mono and bis-Schiff bases synthesized from condensation involving the amine group of 3-amino-1,2,4-triazole and 3,5-diamino-1,2,4-triazole with the carbonyl group of several aromatic aldehydes and ketones along with their transition metal complexes which were characterized by physical, spectral and chemical properties. In most of the studies highlighting the biomedical assessment of imine functionalized compounds, metal complexes showed outstanding results in comparison to free ligands. [ABSTRACT FROM AUTHOR]

Quinoxaline moieties have been subject of voluminous research for their use as precursors and intermediates in drug discovery, due to their diverse therapeutic potentials. Derivatives of quinoxaline have been reported to possess antibacterial, antifungal, antitubercular, antitumor, antidiabetic, anti-inflammatory, anticonvulsant, antiprotozoal and insecticidal activities as well as kinase inhibitors. Owing to the drug-resistance issues associated with existing drugs, strategies to improve the mode of action of these compounds by complexing them to transition metal ions are a current endeavor. Such combinations have demonstrated improved biological activities relative to the individual quinoxaline derivatives, which is attributed to increased liposolubility. The present manuscript reviews therapeutic roles of metal complexes of functionalized quinoxaline motifs for their application in drug development. The structure of the compounds, the DNA binding studies, electrochemical behavior, DFT studies, molecular docking studies, and the mechanism of action of the complexes are also included in the discussion. [ABSTRACT FROM AUTHOR]

In this article, we give a short overview of the theoretical background and properties of the unique polyoxovanadate K6[VIV15As6O42(H2O)]·8H2O (abbreviated V15) containing a cluster of the fifteen VIV ions and exhibiting layers of different magnetizations. Analysis of the magnetic and spectroscopic properties of this fascinating system constitutes a distinct trend in the study of complex nanoscopic polyoxometalates. V15 cluster exhibits strong magnetic anisotropy closely related to the unquenched orbital angular momentum in the degenerate ground state. The degeneracy is interrelated with the spin frustration in V15 which gives rise to a variety of interesting phenomena observed in this polyoxovanadate. We summarize the studies of the isotropic and antisymmetric exchange interaction and analyze its manifestations in magnetic properties, electron paramagnetic resonance, and inelastic neutron scattering spectra as well as in the spin-phonon relaxation in V15. We briefly discuss also a long coherence time (Rabi oscillations) first discovered in molecular magnets due to which the V15 cluster proved to be a prerequisite for the use of molecular magnets in quantum computing. [ABSTRACT FROM AUTHOR]

In this article, we give a short overview of the theoretical background and properties of the unique polyoxovanadate K6[VIV15As6O42(H2O)]·8H2O (abbreviated V15) containing a cluster of the fifteen VIV ions and exhibiting layers of different magnetizations. Analysis of the magnetic and spectroscopic properties of this fascinating system constitutes a distinct trend in the study of complex nanoscopic polyoxometalates. V15 cluster exhibits strong magnetic anisotropy closely related to the unquenched orbital angular momentum in the degenerate ground state. The degeneracy is interrelated with the spin frustration in V15 which gives rise to a variety of interesting phenomena observed in this polyoxovanadate. We summarize the studies of the isotropic and antisymmetric exchange interaction and analyze its manifestations in magnetic properties, electron paramagnetic resonance, and inelastic neutron scattering spectra as well as in the spin-phonon relaxation in V15. We briefly discuss also a long coherence time (Rabi oscillations) first discovered in molecular magnets due to which the V15 cluster proved to be a prerequisite for the use of molecular magnets in quantum computing. [ABSTRACT FROM AUTHOR]

Hydrothermal reactions of 1,3-bis(1,2,4-triazol-1-yl)benzene (btb) and M(NO3)2 (M = Co2+ (1), Cu2+ (2)) afforded two new coordination polymers, [Co(btb)2(NO3)(H2O)]n·NO3·H2O (1) and [Cu(btb)2(NO3)2]n (2), respectively. Single-crystal X-ray diffraction reveals that 1 crystallizes in the space group P21/m and 2 crystallizes in the space group Pī, both showing a double-stranded chain structure. The 1-D chains are interconnected via π⋯π interactions to lead to 2-D ladder-like supramolecular architectures. In addition, magnetic behavior and thermal stability of 1 and 2 have been investigated. For 1, weak antiferromagnetic interactions are observed at low temperature, and the data obey the Curie-Weiss law χM = C/(T−θ), with C = 3.22 cm3·mol−1·K and θ = −10.39 K. For 2, the decrease of the χT vs. T curve at low temperature is the result of intermolecular antiferromagnetic magnetic interactions. [ABSTRACT FROM AUTHOR]

Two transiton metal phosphonates, Cd2[OOCC5H3NPO3H]2·H2O (1) and Zn[OOCC5H4NPO3]·H2O (2), were synthesized by hydrothermal reactions. Single-crystal X-ray diffraction analyses show that both have a 3-D framework. In1, the asymmetric [Cd–NO5] octahedron is connected to the [P–CO3] tetrahedron through corner sharing and two neighboring [Cd–NO5] octahedra are bridged via a mutual plane [O1–O2–O3]. Compound2has a scales-like multilayer structure viewing frombandc. [Zn–O4] tetrahedra linked [P–CO3] tetrahedra through corner O sharing. The thermogravimetric properties and luminescence spectra of1and2were investigated. Compound2emitted a purple-blue light upon 323 nm excitation. Above 100 nm, red shifts in both compounds make them candidates for luminescent materials. [ABSTRACT FROM PUBLISHER]

The coordination behavior of the 2,6-dimethanol pyridine (H2-pdm) with Group 4 and 5 metal alkoxides was undertaken through a series of alcoholysis reactions. The products were crystallographically identified as: (OR)2M(μ2-pdm)[(μ-pdm)M(OR)2]2(M = Ti, OR = OPri(1· py), ONep (2· HONep, tol); Zr, OBut(3)), [M3(μ3-pdm)(μ-pdm)2(μ-ONep)2(ONep)4] (M = Zr (4), Hf (5)), [M(μ-pdm)(OR)3]2[M/OR = Nb/OEt (6), and Ta/ONep (7)] where μ = η1,η1,η2(O,N,O′), μ2 = η2,η1,η2(O,N,O′), μ3 = η1,η1,η3(O,N,O′), OEt = OCH2CH3, OPri = OCH(CH3)2, OBut = OC(CH3)3, and ONep = OCH2C(CH3)3. For each complex, pdm was a bichelating (O,N,O′) ligand generating trinuclear species coupled with a variety of additional bridging modes: μ, μ2, and μ3. Further analyses by multinuclear and DOSY NMR studies indicated that the structures were retained in solution. The coordination behavior of 2,6-dimethanolpyridine (H2-pdm) with Group 4 and 5 metal alkoxides was crystallographically determined. The pdm ligand was found to undergo a variety of tridentate, bridging coordination configurations: (OR)2 M(μ2–pdm)[(μ–pdm)M(OR)2]2(shown), M3(μ3–pdm)(μ–pdm)2(OR)6, or [M(μ–pdm)(OR)3]2. [ABSTRACT FROM AUTHOR]

A new iron(III)/vanadium(III) phosphate, K3[Fe3.26V0.74(OH)O(PO4)4(H2O)2]·2H2O (1), has been obtained by hydrothermal synthesis and characterized by single crystal X-ray diffraction, Scanning electron microscopy–energy dispersive X-ray spectroscopy, Inductively coupled plasma atomic emission spectroscopy (ICP), thermogravimetric analysis, and FTIR spectroscopy. Single crystal X-ray diffraction reveals a 3D open framework (monoclinic, space groupP21/n,a = 9.6391(7) Å,b = 9.8063(7) Å,c = 9.7268(7) Å,β = 100.71(1)°, andV = 903.38(11) Å3). This structure presents FeIIIand VIIIin a 4.4 : 1 M ratio with the metal ions in two different crystallographic sites. Both metallic centers have distorted octahedral environments, linked by PO4tetrahedra, forming channels along thea-axis. The asymmetric unit of K3[Fe3.26V0.74(OH)O(PO4)4(H2O)2]·2H2O presents a {M4(OH)O(PO4)4(H2O)2}3−anionic entity, charge balanced by three K+, which are located within the channels. It is also possible to distinguish M4O2units whose MIIIpolyhedra are linked by vertex and edges. [ABSTRACT FROM AUTHOR]

Two new supramolecular compounds, [Zn2(L)3(4,4′-bpy)(OH)]n(1) and [Cd(L)2(2,2′-bpy)(H2O)]·2H2O (2) (HL = 2-(4-isopropylbenzoyl)benzoic acid, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine), have been hydrothermally synthesized and characterized by elemental analysis, infra-red spectroscopy, thermal gravimetric analyzes, and single-crystal X-ray diffraction.1exhibits 1-D chain and2is 0-D mononuclear. They are both linked into 2-D supramolecular layers by non-covalent interactions. Luminescence properties were also investigated. [ABSTRACT FROM AUTHOR]

A systematic search of the Cambridge structural database was undertaken to quantify the trans influence in square planar and octahedral transition metal compounds. For square planar geometry, d8metal centers were studied, while octahedral searches focused on low-spin d6complexes. Two probe ligands (PL) were used to measure the effect of the trans ligand (TL), chloride, and triphenylphosphine (PPh3). For the TLs O=CX2, NR3, pyridine, and Cl−(X = any non-metal, R = H or hydrocarbon), the effects on the metal–probe ligand (M–PL) distance were statistically equal and were taken as essentially no trans influence. The other ligands studied showed significant decrease in the mean M–PL bond order, relative to the above ligands: SR2 = 0.941; S=CX2 = 0.887; PPh3 = 0.825; phenyl = 0.743; CR3 = 0.719; hydride = 0.685. Some variation in the trans influence is observed, based on the geometry of the metal center and the PL. In general, electron-donating, σ-bonding ligands lead to a larger trans influence, but π-bonding effects can also be important, particularly when the probe ligand also has π-bonding properties. [ABSTRACT FROM AUTHOR]

Two new coordination polymers, [Zn(p-CH3C6H5SO3)2(bpp)2] n (1) and [Cu2(SCN)2(NO3)2(bpp)4] n (2) (bpp = 1,3-bis(4-pyridyl)propane), have been synthesized and characterized. Single crystal X-ray diffraction analysis reveals that 1 and 2 exhibit 2-D layer networks composed of alternate left-handed and right-handed bpp-containing helical chains by sharing Zn(II) in 1 and Cu(II) in 2. Compound 1 exhibits a 2-D undulated double-helical network, while 2 shows a two-fold interpenetrated 2-D double-helical network. p-Toluene sulfonates select Zn2+ rather than Cu2+ to coordinate, while both SCN− and select Cu2+ rather than Zn2+, indicating that the specific organic ligand shows preference/selectivity when different types of metal ions are concurrently present. As a consequence, anionic ligands of different structures impose remarkable influence on the structures of the resultant compounds. Compound 1 shows a broad peak at 415 nm in its emission spectrum, indicating an efficient energy transfer. [ABSTRACT FROM AUTHOR]

A series of transition metal (Zn, Cu, Mn) complexes with chelidamic acid (2,6-dicarboxy-4-hydroxypyridine, H3CAM) and 4,4′-bipyridine (bipy), [Zn2(bipy)Cl2] n (1), {[Zn2(HCAM)(H2CAM)2] · (bipy) · 3.5H2O} n (2), [Mn3(HCAM)3(H2O)7] · (bipy) · 3H2O (3), [Mn2(HCAM)2(bipy) · (H2O)2] · 4H2O (4), [Cu2(HCAM)2(bipy) · (H2O)2] · 4H2O (5), and Cu2(HCAM)2(bipy) · (H2O)2 (6), have been synthesized by hydrothermal or solution methods and characterized by single-crystal X-ray diffraction. The structural analyses reveal that 1 exhibits a zigzag chain of Zn(II), Cl−, and 4,4′-bipyridine. In 2, a 1-D polymeric [Zn2(HCAM)(H2CAM)2] n chain and a discrete 4,4′-bipyridine assemble into a 2-D supramolecular network via H-bonds. Complex 3 consists of asymmetric units of Mn3(HCAM)3(H2O)7 that are linked by hydrogen bonds to form a 2-D H-bonded network. Complexes 4–6 are isomorphous and possess discrete structures. The photoluminescent properties of 1–6 at room temperature were studied. [ABSTRACT FROM PUBLISHER]

New chromium(III) complexes are synthesized by classical thermal and microwave (MW)-irradiated techniques. The Schiff bases 2-acetylfuran-S-benzyldithiocarbazate (L1H), 2-acetylthiophene-S-benzyldithiocarbazate (L2H), 2-acetylpyridine-S-benzyldithiocarbazate (L3H), and 2-acetylnaphthalene-S-benzyldithiocarbazate (L4H) were prepared by condensation of -S-benzyldithiocarbazate in ethanol with the respective ketones by using MW as well as conventional methods. The chromium(III) complexes have been prepared by mixing CrCl3 · 6H2O in 1 : 1 and 1 : 2 molar ratios with monofunctional bidentate ketimines. The structure of the ligands and their transition metal complexes were confirmed by elemental analysis, melting point determinations, molecular weight determinations, infrared (IR), electronic and electron paramagnetic resonance (EPR) spectral, and X-ray powder diffraction studies. On the basis of these studies it is clear that the ligands coordinated to the metal atom in a monobasic bidentate mode by S∩N donors. Thus, an octahedral environment around the chromium(III) has been proposed. The growth inhibiting potential of the ligands and complexes has been assessed against a variety of fungal and bacterial strains. [ABSTRACT FROM AUTHOR]

A series of air-stable, low-spin Ru(III) octahedral complexes [RuX(EPh3)L] (where X = Cl/Br; E = P/As; and L = dibasic tetradentate Schiff base derived by condensation of ethylenediamine with acetoacetanilide/acetoacetotoluidide/ethylacetoacetate in 1 : 2 molar ratio in ethanol) have been synthesized from RuX3(EPh3)3 (where X = Cl/Br and E = P/As) with Schiff bases in 1 : 1 molar ratio in benzene for 6 h. These complexes were characterized by elemental analysis, spectral methods (Fourier transform infrared (FT-IR), UV-Vis, 1H- and 13C-nuclear magnetic resonance (NMR) for the ligands, and electron paramagnetic resonance (EPR)), and are examined electrochemically. The complexes were efficient catalysts for oxidation of primary and secondary alcohols in their corresponding aldehydes and ketones in the presence of molecular oxygen. These complexes were also tested for their antibacterial and antifungal activities. [ABSTRACT FROM AUTHOR]

Using 3,5-pyrazoledicarboxylic acid (H3pdc), 2,2-bipyridine (2,2-bipy) and NaN3, a dinuclear nickel(II) compound with dissimilar bridges, [Ni2(2,2-bipy)2(pdc)(N3)(H2O)2] ⋅ 2H2O (1), has been isolated under hydrothermal conditions. Compound 1 is dinuclear, bridged by two nitrogens in the pyrazole ring of pdc3- and µ1,3 [image omitted]. The dinuclear units and lattice water molecules are further linked by extensive hydrogen bonds to form 2-D infinite planes, which are further linked through π-π stacking to construct a 3-D supramolecular structure. Variable temperature magnetic susceptibility of 1 from 2 to 300 K indicates anti-ferromagnetic interactions. The magnetic exchange coupling constants J = -12.65 cm-1 and zj ' = 3.34 cm-1 for 1 can be obtained through the fit of the magnetic data. [ABSTRACT FROM AUTHOR]

To understand the effects of picolinamide-like ligands on reaction equilibrium, a series of picolinamide derivatives were synthesized and the interactions between the diperoxovanadate complex [OV(O2)2L]- (L = D2O or HOD, abbr. bpV) and picolinamide ligands in solution were explored using multinuclear (1H, 13C, and 51V) magnetic resonance, COSY, and HSQC in 0.15 mol L-1 NaCl ionic medium for mimicking physiological conditions. Formation constants among the picolinamide-like ligands are N-(1-hydroxypropan-2-yl)-picolinamide ≈N-(2-hydroxypropyl)-picolinamide>N-(3-hydroxypropyl)-picolinamide>N-propyl-picolinamide. The substituting group influences the equilibrium by electronic effects. The interactions result in a series of new seven-coordinate diperoxovanadate species [OV(O2)2L']- (L' = picolinamide-like ligands). [ABSTRACT FROM AUTHOR]

Primary phosphine complexes of transition metals have been synthesized from salicylaldiminopropylphosphine. The complexes were characterized by elemental analysis, infrared, electronic, 1H NMR, 31P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate square planar geometry for copper, cobalt, and nickel complexes. The EPR spectra of copper complex in acetonitrile at 300 and 77 K were recorded. The biological activities of the ligand and metal complexes have been studied on microorganisms such as Salmonella typhi, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by the well-diffusion method. The zone of inhibition values were measured at 37°C for 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. The copper(II) complex oxidizes cinnamaldehyde using hydrogen peroxide as oxidant. [ABSTRACT FROM AUTHOR]

A three-dimensional complex, [CuL2(H2O)]2 (HL = 3-hydroxy-1-adamantanecarboxylic acid), C44H64Cu2O14, was synthesized under hydrothermal conditions from CuCO3 · Cu(OH)2 and HL. The crystal structure of the complex was determined by X-ray crystallography and its thermal behavior and IR spectra examined. The non-isothermal dehydration kinetics of the complex were investigated using the Achar differential method. [ABSTRACT FROM AUTHOR]

A CuII complex with 1,2-phenylenediacetate, {[Cu2(PDA)2(DMF)2] · 2H2O}n (H2PDA = 1,2-phenylenediacetic acid), was synthesized and characterized by elemental analysis, IR, UV, EPR, TG and single-crystal X-ray diffraction. The complex crystallizes in triclinic system, space group [image omitted] with a = 10.8156(3) Å, b = 11.2137(3) Å, c = 14.8172(1) Å, α = 72.0670(10)°, β = 81.8790(10)°, γ = 61.7230(10)°, V = 1505.71(6) Å3, Z = 2, and R1 = 0.0768 for 4387 observed reflections. The complex has a 1D structure, in which two adjacent copperII centers are linked by 1,2-phenylenediacetate ligands. The 1D structure are further aggregated via C-H·· · π interactions to a 2D sheet. [ABSTRACT FROM AUTHOR]

Dipeptides glycyl-L-serine and L-seryl-L-tyrosine are tridentate ligands in coordination with Cu(II) through their NH2-, N-(from deprotonated amide group) and O-atom (by COO- group), forming [CuII(LH-1)H2O]. The forth position of square-planar geometry of Cu2+ is occupied by H2O as terminal ligand. Solid-state linear dichroic IR-spectroscopy, UV-Vis, mass spectrometry with ESI and FAB, tandem mass spectrometry (HPLC-MS/MS), TGV and DSC methods, EPR and magnetochemistry data prove the formation of five-membered chelate rings with participation of Cu2+ both in solution and in solid state. [ABSTRACT FROM AUTHOR]

A cobalt(II) compound, [Co4(L)2(OH)2(phen)2(H2O)4] · 6H2O (1), and a copper(II) compound, [Cu2(L)2(H2O)2][Cu(H2O)6] · 6H2O (2) [where H3L is 2-hydroxy-3-[(2-sulfoethylimino)-methyl]-benzoic acid and phen is O-phenanthroline], were prepared and characterized. The tetranuclear cobalt complex 1, C44H62N6O28S2Co4, crystallizes in the monoclinic space group P21/c, with a = 11.847(10) Å, b = 19.061(15) Å, c = 12.635(10) Å, β = 105.483(9)°, and Z = 2; R1 for 4821 observed reflections [I > 2σ(I)] was 0.0679. Complex 1 is a centrosymmetric tetranuclear cobalt complex with all cobalts having distorted octahedral geometry. The molecule can be viewed as two planar [Co2(OH)(L)(Phen)H2O] units tied together by two terminal water molecules. The framework of 1 has the appearance of two connected face-sharing cubes, each with one vertex missing. The trinuclear copper complex 2, C20H44Cu3N2O26S2, crystallizes in the triclinic space group P1, with a = 7.524(1) Å, b = 7.902(2) Å, c = 16.885(4) Å, α = 88.993(6)°, β = 80.725(7)°, γ = 66.725(4)° and Z = 1; R1 for 4298 observed reflections [I > 2σ (I)] was 0.0360. Complex 2 is an ionic compound, in which the three Cu(II) centers have two coordination modes. The molecule has a centrosymmetric dinuclear copper coordinated anion and a hexa-aqua-copper cation. The sulfonic acid group has less coordination ability than carboxylate oxygen. [ABSTRACT FROM AUTHOR]

The coordination chemistry of N'-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)methylene)-2-hydroxybenzohydrazide with copper(II), nickel(II), cobalt(II), manganese(II), zinc(II), palladium(II), iron(III), ruthenium(III), uranyl(VI), and titanium(IV) has been studied. The ligand and its complexes was characterized by elemental and thermal analyses, magnetic moments and conductivity measurements as well as spectroscopic techniques such as infrared, mass spectra, nuclear magnetic resonance, electron spin resonance and electronic absorption spectra. The spectral data showed that the ligand is monobasic tridentate coordinated via the enolic carbonyl oxygen of the hydrazide moiety, azomethine nitrogen and pyrazolone oxygen atoms. [ABSTRACT FROM AUTHOR]

Three new compounds, [Cd(μ3-Hpdh)(μ2-Cl)]n (1), Mn(Hpdh)2(H2O)2 (2) and Zn(Hpdh)2 (H2O)2 (3) (H2pdh = pyridine-2,3-dicarbo-2,3-hydrazide), have been synthesized and characterized by elemental analysis, IR spectra, TG and single-crystal X-ray diffraction. Under hydrothermal conditions, H2pdh is generated by an in situ acylation of H2pda (H2pda = pyridine-2,3-dicarboxylic acid) with hydrazine hydrate. Complex 1 features a 2D layer structure constructed by a dinuclear Cd(II) building block. In complexes 2 and 3, hydrogen bonding interactions connect mononuclear structures into 3D supramolecular frameworks. [ABSTRACT FROM AUTHOR]

Hydrothermal reactions have been exploited in the syntheses of two new metavanadates, {[Co(dpa)2]2V4O12} · H2O (1) and {[Ni(dpa)2]2V4O12} · H2O (2), which were characterized by X-ray diffraction, IR and thermogravimetric analysis. Crystal data: C40H38N12O13Co2V4 (1) monoclinic. P2(1), a = 10.126(2), b = 17.639(4), c = 12.930(3) Å, α = 90°, β = 98.356(4)°, γ = 90°, Z = 2; C40H38N12O13Ni2V4 (2) monoclinic. P2(1), a = 10.1037(9), b = 17.6680(14), c = 12.8832(10) Å, α = 90°, β = 98.423(2)°, γ = 90°, Z = 2. The two complexes are isomorphic and their structures consist of a [V4O12]4- cluster bound to two [M(dpa)2]2+ moieties through the terminal oxygen atoms in a trans-conformation; the [V4O12]4- cluster adopts a chair-like configuration. [ABSTRACT FROM AUTHOR]

Two copper(II) triphosphonate compounds, Cu[(APTPH4)(phen)(H2O)] · 2.16H2O (1) and [Cu(APTPH4)(2,2'-bipy)(H2O)] · 2.63H2O (2), have been prepared by a low temperature hydrothermal reaction from 1-aminopropane-1,1,3-triphosphonic acid (APTPH6), CuO and a second ligand, phen = 1,10-phenanthroline, or 2,2'-bipy = 2,2'-bipyridyl. These two compounds were characterized by single crystal X-ray diffraction, elemental analysis, IR and TG. Crystal data for 1: Monoclinic, space group P21/c, a = 14.4830(7) Å, b = 9.1721(5) Å, c = 16.7403(8) Å, β = 90.101(2)°. For compound 2: Triclinic, space group P1, a = 7.1215(7) Å, b = 10.460(2) Å, c = 14.671(2) Å, α = 82.983(2)°, β = 83.882(2)°, γ = 80.617(2)°. In both compounds, each Cu2+ ion is five-coordinate with two oxygen atoms from the triphosphonate, two nitrogen atoms from the second ligand and one water molecule, to form a distorted square-pyramidal geometry. Both complexes have 3D supramolecular structures constructed by hydrogen bonds and π-π stacking interactions. [ABSTRACT FROM AUTHOR]

Two new coordination supramolecular complexes based on a versatile and unsymmetrical 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and MnII and NiII have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of MnCl2 · 4H2O with Hpot afforded a neutral mononuclear complex [Mn(pot)2(H2O)4] · 2H2O (1), which exhibits a three-dimensional (3-D) supramolecule through versatile intermolecular O-H ··· X (X=O, N and S) hydrogen bond interactions. When using NiCl2 · 6H2O instead of MnCl2 · 4H2O under similar reaction conditions, a neutral mononuclear complex [Ni(pot)2(H2O)4] (2) is also obtained, which does not exhibit intermolecular hydrogen bonds and π-π stacking interactions. It is very interesting that the pot anion exhibits different coordination modes in complexes 1 and 2. The IR spectra and the TGA for 1 and 2 have been investigated and discussed in detail. [ABSTRACT FROM AUTHOR]

Ruthenium(III) complexes of the type trans-[Ru(L)2(AsPh3)2]Cl (L = mono anions of 4-hydroxy-3-(p-X-phenylazo)-benzopyrane-2-one derivatives (For L1, X = H; L2, X = CH3; L3, X = Cl; and L4, X = NO2; AsPh3 = triphenylarsine) have been synthesized and characterized by elemental analysis, spectroscopic (IR, UV-VIS and ESR), magnetic and cyclic voltammetric techniques. The mechanism and the catalytic oxidation of benzyl alcohol, cyclohexanol and cinnamyl alcohol by trans-[Ru(L1)2(AsPh3)2]Cl with hydrogen peroxide as co-oxidant were described. [ABSTRACT FROM AUTHOR]

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L1), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L2) have been synthesized and structurally characterized. Complex Ni(L1)Cl2 · CH3CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L1)(CH3CN)Cl2 (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl2 · CH3CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl2 · CH3CN (4), for ethylene polymerization were studied under activation with MAO. [ABSTRACT FROM AUTHOR]

A new binuclear copper(II) complex [Cu2(oxpn)(IM2py)2](ClO4)2, containing four spin carriers with pyridyl-substituted nitroxide radicals has been synthesized and characterized structurally and magnetically (oxpn = N,N'-bis(3-aminopropyl)oxamido, IM2py = 2-(2'-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl). The structure of the complex consists of centrosymmetric trans oxamido-bridged copper(II) binuclear units and nitroxide radicals. The coordination geometry around each copper atom is distorted square pyramidal and the apical position is occupied by a nitrogen atom of the imidazoline ring of a radical ligand. Magnetic analysis indicates that the complex exhibits strong antiferromagnetic coupling between copper(II) ions through the oxamido bridge and a ferromagnetic interaction between copper(II) ions and radical ligands. The magnetic behaviour is discussed with reference to the crystal structure. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and tg-dsc study of Ln(tfa)3 · 3aza where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb and Er, tfa = trifluoroacetate and aza = 2-azacyclononanone are reported. The obtained X-ray powder diffraction patterns show that the compounds are divided in two isomorphous groups: La, Pr, Nd and Eu, Sm, Gd, Tb and Er. For all compounds, the thermodegradation under nitrogen gave the respective oxifluorides (LnOF) as the final product. The melting temperature intervals are 105-110°C, 100-112°C, 90-95°C, 79-101°C, 65-70°C, 75-90°C, 64-76°C and 50-65°C for the La, Pr, Nd, Sm, Eu, Gd, Tb and Er compounds, respectively, and it is verified that the lanthanide contraction induces a weaker intermolecular interaction between adjacent molecules in the solid state. [ABSTRACT FROM AUTHOR]

A new Schiff base ligand, 2,4-dichloro-6-(cyclopropyliminomethyl)phenol, and a copper(II) complex containing it have been synthesized and characterised. The ligand and complex crystallise in space groups Cmca and C2/c, respectively. In the complex, the Cu atom is four-coordinate (distorted tetrahedral), bonded to two imine N and two phenolate O atoms from two Schiff base ligands. Bond lengths associated with the donor atoms in the complex are different to those in the ligand. The structure is compatible with spectra of the bulk sample. [ABSTRACT FROM AUTHOR]

The oxo-bridged dinuclear complex [(μ-O){ReOCl2(pimH)}2] · 2H2O · 2DMF was prepared by reaction of trans -[ReOCl3(PPh3)2] and 2,6-bis(2-benzimidazolyl)pyridine (pimH2) in acetonitrile, with recrystallization from CH2Cl2/DMF. An X-ray crystallographic study shows that pimH is coordinated as a tridentate monoanionic chelate, with deprotonation of an imidazolyl N(1)H group. The axis of the molecule is formed by the O=Re–O–Re=O moiety, with the bridging oxygen lying on a crystallographic inversion center. The two O–Re=O angles are therefore equal [172.7(1)°]. [ABSTRACT FROM AUTHOR]

In this study, N -(4-{[(2-ethyl-2-methyl-1,3-dioxolan-4-yl)methyl]amino}butyl)- N ′-hydroxy-2-(hydroxyimino)ethanimidamide (L 1 H2) and N ′-hydroxy-2-(hydroxyimino)- N -(4-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]amino}butyl)ethanimidamide (L 2 H2) were synthesized by the reaction of N -[(2-ethyl-2-methyl-1,3-dioxolan-4-yl)methyl]butane-1,4-diamine or N -[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]butane-1,4-diamine and anti -chloroglyoxime. Ligands form mononuclear complexes [(LH)2M] with a metal  :  ligand ratio of 1  :  2 with M  =  Co(II)(H2O)2, Ni(II) and Cu(II). Zn(II) forms complexes [(LH)(H2O)(Cl)Zn] with a metal  :  ligand ratio of 1  :  1. The Co(II) complexes of the ligands are proposed to be octahedral with water molecules as axial ligands, the Ni(II) and Cu(II) complexes are proposed to be square planar, and the complexes of Zn(II) are tetrahedral. A chloride ion and a water molecule are also coordinated to the Zn(II) ion. Structural assignments are supported by elemental analyses, IR, 1 H- and 13 C-NMR spectra, UV–Visible spectroscopy, molar conductivity, magnetic susceptibility measurements and thermogravimetric analyses (TGA). [ABSTRACT FROM AUTHOR]

Tetranuclear heterometallic complexes, [Tb2Zn2(Bzo)10(phen)2] (1) and [Tb2Zn2(TPA)10(phen)2] (2) (Bzo- = C6H5CO-,2, TPA- = o-C4H3SCO-,2, phen = 1,10-phenanthroline), were synthesized by the rheological phase reaction method and characterized by elemental analysis, IR and X-ray crystallography. Both complexes are tetrameric and the carboxylate ligands display three coordination modes, bidentate bridging, bidentate chelating and tridentate chelating-bridging. The Zn atoms in complexes 1 and 2 are coordinated by two nitrogen atoms from one phen ligand, four oxygen atoms from two bidentate bridging and a tridentate chelating-bridging carboxylate group. However the coordination spheres around the Tb atoms are different. The Tb atom in 1 is eight-coordinate, while the Tb atom in 2 is seven-coordinate. Both complexes 1 and 2 exhibit green luminescence when irradiated by UV light. Compared with binary terbium benzoate, the introduction of the Zn2+ ion and phen enhances the luminescence intensity dramatically. [ABSTRACT FROM AUTHOR]

A new organic-inorganic hybrid vanadium oxide complex, [Ni(phen)(H2O)]2V4O12, 1 (phen = 1,10-phenanthroline), has been synthesized using a hydrothermal method and structurally characterized. Complex 1 exhibits a layered structure in which vanadium oxide chains, {V2O6}2n-, n, are linked to [Ni(phen)(H2O)]2+ subunits to form a two-dimensional (2D) topology. Crystals are triclinic, space group P1, with a = 7.869(2), b = 9.437(2), c = 20.992(4) Å, α = 89.95(3), β = 89.84(3), γ = 67.22(3)°, V = 1437.3(5) Å2 and Z = 2. Magnetic measurements indicate that 1 exhibits a weak ferromagnetic exchange interaction. [ABSTRACT FROM AUTHOR]

A new organic-inorganic hybrid vanadium oxide complex, [Ni(phen)(H2O)]2V4O12, 1 (phen = 1,10-phenanthroline), has been synthesized using a hydrothermal method and structurally characterized. Complex 1 exhibits a layered structure in which vanadium oxide chains, {V2O6}2n-, n, are linked to [Ni(phen)(H2O)]2+ subunits to form a two-dimensional (2D) topology. Crystals are triclinic, space group P1, with a = 7.869(2), b = 9.437(2), c = 20.992(4) Å, α = 89.95(3), β = 89.84(3), γ = 67.22(3)°, V = 1437.3(5) Å2 and Z = 2. Magnetic measurements indicate that 1 exhibits a weak ferromagnetic exchange interaction. [ABSTRACT FROM AUTHOR]

Two series of dicopper(II) complexes derived from bis( N- salicylidine)dicarboxylic acid dihydrazides (H 4 L n ) of general formula [Cu 2 (L n )· x H 2 O]· y H 2 O and [Cu 2 (H 2 L n )Cl 2 · x H 2 O]· y H 2 O have been synthesized and characterized, where n refers to the number of carbon atoms in the aliphatic spacer between the two N- salicylideneacylhydrazine units. Magnetic susceptibility measurements for neutral dicopper(II) complexes [Cu 2 (L n )· x H 2 O]· y H 2 O indicate significant antiferromagnetic coupling between copper(II) centers. The -2 J values obtained from the Bleany-Bowers equation are within the range 121-223 cm -1 , suggesting association of the coordinated copper(II) units Cu(ONO) via phenoxy bridges. This leads to a polynuclear structure in which the dimeric units are connected with the aliphatic spacer. From the best-fit values of the mole fraction of paramagnetic uncoupled copper(II) centers ( ρ ), the degree of association in these polynuclear copper(II) complexes has been estimated. The chloro dicopper(II) complexes [Cu 2 (H 2 L n )Cl 2 · x H 2 O]· y H 2 O with n = 0, 2 and 3 also show strong antiferromagnetic exchange coupling (-2 J = 215-423 cm -1 ), suggesting a polynuclear structure in which the copper(II) is in a distorted square-pyramidal environment, bound in the equatorial plane with a monoanionic ONO tridentate acylhydrazone unit and the μ-phenoxy oxygen and the axial site occupied by a chloride. The dicopper(II) complexes with n = 1 and 4 show weak antiferromagnetic exchange coupling (-2 J = 16-20 cm -1 ). In these complexes the chloride ion may occupy the fourth equatorial site while the μ-phenoxy is in the apical position. [ABSTRACT FROM AUTHOR]

5,5′-methylene bis( N -salicylideneacetylhydrazine) (H 4 LMe) and 5,5′-methylene bis( N -salicylidenebenzoylhydrazine) (H 4 LPh) were prepared and characterized by elemental analysis, IR, Uv-Vis, 1 Hnmr and EI mass spectra. These acylhydrazones were found to act as dinucleating bis(tridentate) ligands and a number of copper(II) complexes with formulas: i) [{Cu 2 (LMe) H 2 O} x ] and [{Cu 2 (LPh)0.5H 2 O} x ]1.5H 2 O, ii) [{Cu 2 (H 2 LMe)Cl 2 } x ] and [{Cu 2 (H 2 LPh)Cl 2 } x ] iii) [{Cu 2 (H 2 LMe)} x ] x (NO 3 ) 2 and [{Cu 2 (H 2 LPh)} x ] x (NO 3 ) 2 were prepared and characterized. Magnetic susceptibility measurements at different temperatures (4.5-300 K) revealed that both neutral [{Cu 2 (LMe)H 2 O} x ] and [{Cu 2 (LPh)0.5H 2 O} x ] x 1.5H 2 O (-2J = 197-200 cm -1 ) and nitrate [{Cu 2 (H 2 LMe)} x ] x (NO 3 ) 2 and [{Cu 2 (H 2 LPh)} x ] x (NO 3 ) 2 (-2J = 199-203 cm -1 ) complexes show strong antiferromagnetic spin-spin coupling, implying association via phenoxy oxygens and coplanar Cu 2 O 2 bridges with the Cu(II) coordination plane. The chloro complexes, on the other hand, show weak antiferromagnetic exchange coupling (-2J = 6-9 cm -1 ) implying association but with perpendicular Cu 2 O 2 bridges. [ABSTRACT FROM AUTHOR]

A novel compound formed by copper(II) and picolinic acid of formula [Cu(PCA) 2 (H 2 O) 2 ] (PCA = picolinate) has been synthesized. The complex crystallizes in the monoclinic space group P 2 1 / c with a = 5.4479(11), b = 10.910(2), c = 10.396(2) Å, β = 98.22(3)° and Z = 2. X-Ray analysis reveals that the Cu(II) ion lies in the usual distorted octahedral environment; two nitrogen atoms and two oxygen atoms from the PCA form the basal plane and two oxygen atoms from coordinated water molecules occupy the axial position. [Cu(PCA) 2 (H 2 O) 2 ] units are connected in a three-dimensional structure by intermolecular hydrogen bonds. [ABSTRACT FROM AUTHOR]

The interactions of cephalexin (Hcepha) with transition and d 10 metal ions have been investigated. The complexes [M(cepha)Cl]nH 2 O [M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II)] were characterized by physicochemical and spectroscopic methods. The IR and 1 H NMR spectra of the complexes suggest that cephalexin behaves as a monoanionic tridentate ligand. In vitro antibacterial activities of Hcepha and the complexes were tested. [ABSTRACT FROM AUTHOR]

In line with our investigations of rhenium nitrosyl complexes, we have studied the reaction of [ReCl 3 (NO)(OPPh 3 )(PPh 3 )] with pyridine. The [ReCl 2 (NO)(py) 3 ] complex obtained in this reaction has been characterised by IR, electronic spectra and magnetochemical measurements; ligand field parameters and the electronic structure have been determined. The crystal and molecular structure of [ReCl 2 (NO)(py) 3 ] has been solved by the heavy atom method. Crystals of [ReCl 2 (NO)(py) 3 ] contain distorted octahedral molecules with the pyridine ligands in the mer -arrangement. The nitrosyl group is coordinated linearly to the rhenium atom as NO + . [ABSTRACT FROM AUTHOR]

The complex [ReO(Me 4 tu) 4 ] 3+ , with Me 4 tu = tetramethylthiourea, is characterized in nonaqueous media. Its structure is studied in acetonitrile solution by 1 H and 13 C NMR and its electrochemical behavior in the same solvent is analyzed by means of cyclic voltamperometric measurements. Heteronuclear correlation and variable temperature NMR experiments suggest that the complex ion shows a similar structure in solution and in the solid state. At low temperatures (below 0°C) free rotation of the dimethylamine groups around the thiocarbonyl carbon-nitrogen bond is restricted and the dissolved complex adopts the rigid structure observed in the solid state. Cyclic voltamperometric results suggest that the redox behavior of this compound can be explained through an E r C i E r mechanism (a chemical reaction coupled between two electron-transfer reactions). An initial one electron reduction of the complex from Re(V) to Re(IV) followed by an irreversible chemical reaction, leads to a new electroactive species of Re(IV)*, which is reduced to Re(III). The ability of [ReO(Me 4 tu) 4 ](PF 6 ) 3 to serve as a precursor for other Re(V) complexes by ligand substitution is established, in acetone solution, with different kinds of incoming ligands: diethyldithiocarbamate (Et 2 dtc), ethylenediamine (en) and pyridine (py). The previously known complexes $ [{\mathop{\rm Re}\nolimits} _2^{\rm V} {\rm O}_3 ({\rm Et}_2 {\rm dtc})_4 ] $ , [Re V O 2 (en) 2 ](PF 6 ) and [Re V O 2 (py) 4 ](PF 6 ) are easily synthesized under mild conditions with high yields. [ABSTRACT FROM AUTHOR]

A novel solid oxovanadium(V) complex, monoaqua(8-hydroxyquinolinato)dioxovanadium(V), VO 2 (H 2 O)(Q) (Q = 8-hydroxyquinolinate ion) was synthesized and characterized by FTIR and UV/Vis spectroscopy, voltammetric measurements and Hartree-Fock ab initio calculations on the models of the ligand Q and the respective phenol QH. Electrochemical measurements in solution clearly showed complex formation between NH 4 VO 3 and 8-hydroxyquinoline, revealing an electrode reaction of the intermediate NH 4 [VO 2 (Q)OH] species on the mercury electrode in 0.1 M NH 3 /NH 4 Cl buffer (pH 9.85) as a reversible process at -0.700 V ( vs . Ag | AgCl | KCl sat reference electrode). The square-wave voltammogram of an aqueous solution of the VO 2 (H 2 O)(Q) complex obtained with thermal deamination of NH 4 [VO 2 (Q)OH] presented a new reversible peak at -0.720 V. [ABSTRACT FROM AUTHOR]

In this study, 1,2-dihydroxyimino-3,7-di-aza-9,10- O -α-methyl benzal decane (LH 2 ) was synthesized starting from 1,2- O -α-methyl benzal-4-aza-7-amino heptane (RNH 2 ) and antichloroglyoxime. With this ligand, complexes were synthesized using Ni(II) and Cu(II) salts with a metal : ligand ratio of 1 : 2. However, the reaction of the ligand with salts of Zn(II) and Cd(II) gave products with metal : ligand ratio of 1 : 1. Structures of the ligand and its complexes are proposed based on elemental analyses, IR, 13 C- and 1 H-NMR spectra, magnetic susceptibility measurements and thermogravimetric analyses (TGA). [ABSTRACT FROM AUTHOR]