Synthesis,characterization and antitumor activity of benzalde- hyde nitrogen mustard picolinoyl hydrazone complexes

CuII, NiII, CoII, ZnII and CdII complexes of picolinamido-4-bis(2-chloroethyl)aminobenzaldimine (PBAB) have been synthesized and characterized by elemental analysis, conductivity, i.r. u.v.-vis. and e.p.r. spectra. The results suggest a square planar structure for the CuII complex, a tetrahedral geometry for the ZnII and CdII complexes and an octahedral structure for the CoII and NiII complexes. The complexes have been screened for antitumor activity against SMMC-7721 human liver cancer cell line; all of them exhibit biological activity at high concentrations for the cell line studied and a synergic effect between CuII and PBAB is evident.     

Synthesis of a dehydroabietyl derivative bearing a 2-(2'-hydroxyphenyl)benzimidazole unit and its selective Cu²+ chemosensing

A dehydroabietyl derivative 2 bearing a 2-(2'-hydroxyphenyl)benzimidazole unit was synthesized and its sensing behaviors toward metal ions were investigated by UV-Vis and fluorescence spectroscopy methods. In THF solution, compound 2 exhibited excellent selectivity for CuII over miscellaneous other metal ions including CrII, MnII, CoII, NiII, ZnII, CdII, AlIII, MgII, PbII, HgII, NaI, LiI and KI evidenced through the quenching of the fluorescence of the benzimidazole fragment. The reaction between 2 and Cu2+ was found to be stoichiometric with the formation of a 1:1 complex.     

Metallic complexes from 2-furaldehyde semicarbazone and 5-methyl-(2-furaldehyde) semicarbazone

The synthesis and characterization of CoII, NiII, CuII and CdII complexes with 2-furfuralsemicarbazone (FSC) and 5-methyl 2-furfuralsemicarbazone (MFSC) are reported. These ligands lead to the complexes: [ML2X2] or [MLX2] (L = FSC or MFSC) whose structures were determined using elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra as well as by n.m.r. FSC and MFSC act as bidentate ligands in most of the CoII, NiII, CuII and CdII complexes. MFSC is a monodentate ligand in [NiBr2(MFSC)4].     

Polymer complexes. Part XVI. Structural chemistry of poly-(5-vinylsalicylidene)aniline complexes

Transition Metal Chemistry - Poly(5-vinylsalicylidene)aniline homopolymer and polymer complexes of 5-vinylsalicylideneaniline with CuII, CoII, NiII, CdII and $? UO_{2}^{2+}$ have been...     

Structural chemistry of some new azo complexes

The preparation of 2-thiouracil (H2L) and its 5-(2-thiazolylazo)thiouracil (H2L') complexes with CoII, NiII, CuII, ZnII and CdII are reported. The new complexes have been characterized by elemental analyses, solid reflectance, infrared spectra and magnetic susceptibilities. These measurements suggest that, the ligand is bound to the metal ion through nitrogen and/or sulphur atom behaving as mono- or bidentate ligand. Thermal decomposition studies of these metal complexes are explained to give more information on the structure of the investigated chelates. On the basis of the v(OH) bending frequencies and the insolubility of the complexes in common organic solvents, polymeric structures have been proposed.     

New insights into the visible-light-induced DNA cleavage activity of dipyridoquinoxaline complexes of bivalent 3d-metal ions

Dipyridoquinoxaline (dpq) complexes of bivalent 3d-metal ions, viz., [FeII(dpq)3](PF6)2 (1), [CoII(dpq)3](ClO4)2 (2), [NiII(dpq)3](ClO4)2 (3), [CuII(dpq)2(H2O)](ClO4)2 (4), [ZnII(dpq)3](ClO4)2 (5), and [ZnII(dpq)2(DMF)2](ClO4)2 (5a) (DMF = N,N-dimethylformamide), are prepared and their photoinduced DNA cleavage activity studied. Structural characterization for the complexes 1 and 5a is done by single-crystal X-ray crystallography. All the complexes show efficient binding propensity to calf thymus DNA with a binding constant (K) value of approximately 10(5) M(-1). Complexes 1, 2, and 4 show metal-based cyclic voltammetric responses at 1.2, 0.4, and 0.09 V (vs SCE) in DMF 0.1 M [Bun4N](ClO4) assignable to the respective FeIII/FeII, CoIII/CoII, and CuII/CuI couples. The NiII and ZnII complexes do not show any metal-based redox process. The dpq-based reductions are observed in the potential range of -1.0 to -1.7 V vs SCE. DNA melting and viscosity data indicate the groove-binding nature of the complexes. Control experiments using distamycin-A suggest a minor groove-binding propensity of the complexes. The complexes exhibit photoinduced cleavage of supercoiled pUC19 DNA in UV light of 365 nm. The diamagnetic d6-FeII and d10-ZnII complexes are cleavage-inactive on irradiation with visible light. The paramagnetic d7-CoII and d9-CuII complexes exhibit efficient DNA cleavage activity on photoirradiation at their respective d-d band. The paramagnetic d8-NiII complex displays only minor DNA cleavage activity on irradiation at its d-d band. The DNA cleavage reactions at visible light under aerobic conditions involve the formation of hydroxyl radical. The CoII complex shows photocleavage of DNA under an argon atmosphere. Theoretical calculations on the complexes suggest a photoredox pathway in preference to a type-2 process forming singlet oxygen for the visible-light-induced DNA cleavage activity of the 3d-metal complexes. The theoretical data also predict that the photoredox pathway is favorable for the 3d7-CoII and 3d9-CuII complexes to exhibit DNA cleavage activity, while the analogous 3d6-FeII and 3d8-NiII complexes are energetically unfavorable for the exhibition of such activity under visible light. The CoII and CuII complexes are better suited for designing and developing new metal-based PDT agents than their cleavage-inactive FeII, NiII, and ZnII analogues.     

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of conjugated 3-(benzylidene/salicylidene)-β-diketones (having no enolisable γ-carbon proton) and their reactions

Transition Metal Chemistry - The synthesis and structural characterization of new metal(II) chelates (M = CoII, NiII, CuII and ZnII) of neutral conjugated bidentate β-diketone ligands, having...     

Seven-coordination versus six-coordination in divalent first-row transition-metal complexes derived from 1,10-diaza-15-crown-5

The complexes of the heptadentate receptor N,N'-bis(benzimidazol-2-ylmethyl)-1,10-diaza-15-crown-5 (L2) with MnII, CoII, NiII, CuII, and ZnII are reported. The X-ray crystal structures of the ZnII and NiII complexes show that whereas the ZnII ion is seven-coordinated in a (distorted) pentagonal-bipyramidal coordination environment, the NiII ion is only six-coordinated in a distorted octahedral coordination environment. Theoretical calculations on the [M(L2)]2+ systems (M = Mn, Co, Ni, Cu, or Zn) performed at the density functional theory (DFT; B3LYP) level have been used to obtain information about the structure and electronic properties of these complexes, as well as to rationalize their preferences for a pentagonal-bipyramidal or an octahedral coordination. We have found that for the MnII, CoII, CuII, and ZnII complexes, geometry optimizations lead systematically to pentagonal-bipyramidal coordination environments around the metal ions. However, for the NiII complex, two minimum-energy conformations were obtained, with the metal ion being in octahedral (o-[Ni(L2)]2+) or pentagonal-bipyramidal (pb-[Ni(L2)]2+) coordination. The stabilization of the octahedral geometry in the NiII complex can be considered as the result of the Jahn-Teller effect operating in pentagonal-bipyramidal geometry, which in an extreme case leads to an octahedral coordination. Spectrophotometric titrations carried out in dimethyl sulfoxide (DMSO) and CH3CN/DMSO (9:1) solutions indicate the following stability sequence for the complexes of L2: CoII approximately NiII > ZnII > MnII. The variations in the geometry and stability of the complexes may be rationalized in terms of the different occupations of the frontier molecular orbitals along the first-row transition-metal series. Finally, a time-dependent DFT approach was used to investigate the absorption spectrum of the [Cu(L2)]2+ complex based on the optimized geometries at the B3LYP level, also confirming a pentagonal-bipyramidal coordination in solution for this compound.     

Solution and solid studies of some metal complexes with cytosine and its derivatives

Stability constants for the binary (1?:?1) complexes of CoII, NiII, CuII, ZnII, CdII, CaII, SrII and BaII with cytosine, cytidine, 5-bromocytosine, 5-azacytosine and 5-fluorocytosine were determined in aqueous solution (Ionic strength, μ = 0.1?mol?dm^?3 NaNO₃) potentiometrically at 25, 35 and 45°C. Experimental pH titration data were analyzed using the BEST computer program in order to evaluate formation constants of various intermediate species formed in the above binary systems. Enthalpy and entropy changes for the formation of binary complexes were calculated. On the basis of solution studies, efforts were made to prepare the binary complexes with 5-azacytosine ligand. Isolated solid complexes were characterized by different techniques and spectroscopic studies suggested a polymeric nature for the complexes, with OH and 5-azacytosine acting as bridging ligands.     

Application of voltammetric methods for the analysis of gold and other transition metals in quartzite rock

Simple, rapid and accurate voltammetric methods viz. DCP, DPP and DPASV have been presented for the trace determination of gold and other transition metals in quartzite rock sample. The analysis has been performed using 0.1 M(NH4)2 tartrate, 0.1 M NaClO4 and 1 M NaOH as supporting electrolyte with 0.001% gelatin as maximum suppressor. The results show the presence of CuII(10.70), CoII(4.72), FeIII(66.96), AuIII(0.066), ZnII(1.68) and CdII(0.62) mg x g(-1) metal ions from the sample. Gold produced a well defined wave/peak with E1,2/Ep = -0.61 V/-0.64 V vs SCE, in 1 M NaOH supporting electrolyte. The quantitative analysis of metal inos was carried out by the method of standard addition. Statistical treatment of the observed voltammetric data reveals high accuracy and good precision of determination. The observed voltammetric results are comparable with those obtained using AAS method.     

Functional tetrametallic linker modules for coordination polymers and metal-organic frameworks

The new biphenol-based tetranucleating ligand, 2,2',6,6'-tetrakis(N,N-bis(2-pyridylmethyl)aminomethyl)-4,4'-biphenolate, dbpbp2-, comprises two linearly disposed phenolato-hinged dinucleating heptadentate units, each of which offer one O and three N donors to a total of four metal ions. The ligand has been isolated as the zinc chloride complex [Zn4(dbpbp)Cl4]2+, and the ZnII ions have been completely or partially substituted by CuII, FeIII, CoII, and CoIII in metathesis reactions. Similarly, the chloride ligands of [Zn4(dbpbp)Cl4]2+ have been exchanged for solvent molecules (acetonitrile and/or water) and bridging carboxylate ligands. The resulting complexes have been characterized by single-crystal X-ray diffraction, ESI mass spectrometry (ESI-MS), cyclic voltammetry (CV), and EPR spectroscopy. The structures containing [M4(dbpbp)Cl4]2+ with M = ZnII or CuII exhibit 2-D polymeric honeycomb sheets in which intermolecular M...Cl interactions bridge between adjacent [M4(dbpbp)Cl4]2+ cations. Two mixed-metal tetrabenzoate complexes [M4(dbpbp)(O2CC6H5)4]2+/3+ have also been prepared, namely a stoichiometric CuII2ZnII2 complex and a nonstoichiometric FeIII/ZnII system. In the latter case, ESI-MS identifies FeZn3, Fe2Zn2, and Zn4 species, and X-ray crystallography suggests an average composition of Fe0.8Zn3.2. Preparation of a CoII4 complex by metathesis was considerably more difficult than preparation of [Cu4(dbpbp)Cl4]2+, requiring both a large excess of the cobalt source and the presence of auxiliary benzoate. In the presence of 2 equiv of benzoate per starting [Zn4(dbpbp)Cl4]2+ unit and excess CoII, dioxygen binds as peroxide at each end of the molecule to give the CoIII4 complex [Co4(dbpbp)(O2)2(O2CC6H5)2]4+. This latter complex, together with new tetra- and hexametallic benzenedicarboxylato- and benzenetricarboxylato-bridged complexes of dinuclear [Co2(O2)(bpbp)]3+ units (bpbp- = 2,6-bis(N,N-bis-(2-pyridylmethyl)aminomethyl)-4-tert-butyl-phenolate), is a module for potential construction of 1-D and 2-D coordination polymers/metal-organic frameworks (MOFs) capable of reversible O2 binding.     

Molecular tectonics of mixed-ligand metal-organic frameworks: positional isomeric effect, metal-directed assembly, and structural diversification

A series of nine mixed-ligand metal-organic frameworks (MOFs) have been prepared by the combination of a bent dipyridyl linker 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole (bpt) and three benzenedicarboxylate isomers (pa = phthalate, ip = isophthalate, and tp = terephthalate), respectively, with different metal ions such as CoII, NiII, CuII, ZnII, and CdII. The framework structures of these neutral polymeric complexes have been determined by the X-ray single-crystal diffraction technique. Structural analysis reveals that the benzenedicarboxylate isomers display versatile coordination modes to manage the metal ions to form 1-D chain or ribbon arrays, which are further extended via the exo-bidentate bpt connectors to give rise to a variety of coordination networks, such as a simple (4,4) layer, 2-D double layer with decorated (4,4) topology, 2-D layer with decorated (3,6) topology, 2-D bilayer with 82.10 topology (2-fold interpenetration), 3-D polythreaded architecture (1-D + 2-D), and 2-fold interpenetrating porous lattice of (4,4) layers. The accessorial secondary interactions such as hydrogen bonding and/or aromatic stacking are also helpful for the extension and stabilization of the final supramolecular aggregates. This work evidently indicates that the isomeric effect of the anionic benzenedicarboxylate is significant in the construction of these network structures, which are also well regulated by the metal centers. The ZnII and CdII MOFs exhibit strong solid-state luminescence emissions at room temperature, which originate differently from intraligand transition or ligand-to-metal charge transfer. Thermal stability of these crystalline materials has been explored by thermogravimetric analysis of mass loss. The 3-D host frameworks of MOFs 8 and 9 show similar porous cavities, and their desorption/adsorption behaviors of guest solvents have also been investigated.     

Antitumor activity of transition metal(II) complexes with all- trans retinoic acid

Five complexes of transition metals with all-trans retinoic acid (HRA) have been prepared and characterized by elemental analysis, molar conductance, t.g.–d.t.a, i.r., and u.v.-vis. spectroscopy, and 1H-n.m.r. spectrometry. The general formula of these complexes is ML2 ·nH2O where L=RA, M=MnII, CoII, NiII, CuII, ZnII, and n=3 or 4. They have been studied for their antitumour activity against human bladder cancer line EJ (EJ cells) with respect to proliferation, induce differentiation, P21 and mutation P53 expressions in vitro.     

Mononuclear and binuclear chelates derived from potassium benzenesulfonyldithiocarbazate

Benzenesulfonyldithiocarbazate (PhSO2NHNHCSS−) (HBDC−) complexes of CoII, NiII, ZnII, CdII, PdII, PbII, CuI and AgI have been prepared and characterized by elemental analyses, molar conductivities, spectral (vis., i.r, n.m.r.), thermal (t.g.a., d.t.a.) and magnetic moment measurements. The molar conductivities for the complexes lie in the non-electrolyte range. The i.r. spectral data indicate that KHBDC behaves either as monoanionic bidentate or dianionic tridentate ligand. The O=S=O group participates in bonding via bridge formation in dimeric (1:1) complexes. Different stereochemistries are proposed for the CoII, NiII and PdII complexes on the basis of the spectral and magnetic studies. T.g.a. and d.t.a. data suggest a mechanism for degradation of the complexes as a function of temperature. This revised version was published online in June 2006 with corrections to the Cover Date.     

四硫富瓦烯四硫纶桥联金属邻菲啰啉配合物的合成与性质

以2,3,6,7-四(2’-氰乙硫基)四硫富瓦烯为桥配体的前驱物, 合成了标题配合物μ-(ttftt)-[M(phen)]2 (M＝MnII, FeII, CoII, NiII, CuII, ZnII). 配合物的结构和性质经由元素分析、核磁共振波谱、红外光谱、紫外-可见光谱、荧光光谱、摩尔电导率和量子化学计算表征, 研究了电氧化还原和对Li/SOCl2电池的催化特性. 发现铁和钴配合物具有较高的催化活性且有利于电池的大电流和低温放电, 在25 ℃和电流密度25 mA/cm2条件下铁配合物使电池的电压和容量分别提高了133 mV和218 mAh.     

Solid state self-assembly synthesis of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with a bis-Schiff base

Four-coordination compounds of the bis-Schiff base, bis(o-vanillin)-o-phenylenediamine, with CoII, NiII, CuII and ZnII were obtained in high yield by a self-assembly solid state reaction of the metal acetates with o-vanillin and o- phenylenediamine at 60°C. The complexes were characterized by elemental analyses, i.r., u.v., molar conductivities and by powder XRD. The spectroscopic data show that the complexes are pure and are non-electrolytes.     

Formation constants and thermodynamic parameters of α-pyridoin thiosemicarbazones with divalent metal ions

The proton–ligand stability constants of -pyridoin thiosemicarbazone, -pyridoin 2–methylthiosemicarbazone, -pyridoin 4–methylthiosemicarbazone and -pyridoin (4–phenylthiosemicarbazone) as well as the formation constants of their chelates with CuII, NiII, CoII, ZnII and MnII have been determined. The Calvin–Bjerrum pH titration techniques, as modified by Irving and Rossotti, were employed in aqueous media at different ionic strengths and temperatures. The stability constants of the complexes follow the order: CuII > NiII > CoII > ZnII >MnII which is in accord with the Irving–Williams series. The chelates derived from -pyridoin 4–phenylthiosemicarbazone have relatively higher stability constants, which may be attributed to the presence of the benzene ring in the chain.     

Transition metal ion directed supramolecular assembly of one- and two-dimensional polyrotaxanes incorporating cucurbituril

This paper reports a synthetic strategy to construct one- and two-dimensional (1D and 2D) polyrotaxanes, in which a number of rings are threaded onto a coordination polymer, by the combination of self-assembly and coordination chemistry. Our approach to construct polyrotaxanes with high structural regularity involves threading a cucurbituril (CB) "bead" with a short "string" to form a stable pseudorotaxane, followed by linking the pseudorotaxanes with metal ions as "linkers" to organize into a 1D or 2D polyrotaxane. A 4- or 3-pyridylmethyl group is attached to each end of 1,4-diaminobutane or 1,5-diaminopentane to produce the short "strings", which then react with the cucurbituril "bead" to form stable pseudorotaxanes. The reaction of the pseudorotaxanes with various transition metal ions including CuII, CoII, NiII, AgI, and CdII produces 1D or 2D polyrotaxanes, in which many molecular "beads" are threaded onto 1D or 2D coordination polymers as confirmed by X-ray crystallography. The overall structure of a polyrotaxane is the result of interplay among various factors that include the coordination preferences of the metal ion, spatial disposition of the donor atoms with respect to the CB beads in the pseudorotaxane, and the size and coordination ability of the counteranion.     

Nineteen-membered pentaazamacrocyclic complexes bearing tetraamide groups

A new series of CoII, NiII, CuII and ZnII complexes incorporating pentaazamacrocyclic ligands has been prepared via the template condensation of o-aminobenzoic acid with succinic or phthalic acids in the presence of diethylenetriamine. The overall geometry and mode of bonding have been deduced on the basis of elemental analyses, i.r., 1H-n.m.r., e.p.r. and u.v.-vis. spectral studies, and conductivity and magnetic susceptibility measurements. An octahedral geometry is proposed for all the complexes, where five coordination sites are occupied by the macrocyclic nitrogens and the sixth by an anion.     

Synthesis and spectral studies of cobalt(II), nickel(II) and copper(II) complexes of 1-(2-hydroxy-1-naphthyl)-3-(4-X-phenyl)-2-propen-1-ones and their pyridine adducts

Transition Metal Chemistry - Metal(II) chelates of the type ML2nB [M = CoII, NiII and CuII; L = 1-(2-hydroxy-1-naphthyl)-3-(4-X-phenyl)-2-pro-pen-1-one, (X = H, Cl or Me); B = H2O or Py; n = 0, 2]...