Synthesis and characterization of binary and heterobimetallic complexes of dithiofuroate with 3d-metal ions

New complexes [M(dtf)2] (M=MnII or CuII), Cr(dtf)3 and V(dtf)4 (dtf=dithiofuroate) and heterobimetallic complexes M[Cd(dtf)4] (M=VO2+, MnII, FeII, CoII, NiII or ZnII) have been prepared in H2O−EtOH and characterized by elemental analyses, magnetic susceptibility measurements and spectroscopic studies. The known complexes Fe(dtf)3, Co(dtf)3, Ni(dtf)2, and Zn(dtf)2 have been screened towards the bacteria Pseudomonas spergillus and Bacillus spergillus. In vitro results of the binary complexes on P-815 (murine mastocytoma) indicate that these complexes show significant inhibition of [3H]thymidine and [3H]uridine incorporation in DNA and RNA in the tumour cells. This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

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.     

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.     

Facially coordinating cyclic triamines, part I. The coordination chemistry of cis-3,5-diaminopiperidine and substituted derivatives

An efficient and convenient method for the preparation of cis-3,5-diaminopiperidine (dapi) has been established and the coordination chemistry of this ligand with CoII, CoIII, NiII, CuII, ZnII, and CdII has been investigated in the solid state and in aqueous solution. Potentiometric measurements revealed a generally high stability for the bis complexes of the divalent cations with maximum stability for NiII (log beta2 = 21.2, beta2 = [M(dapi)2][M](-1)[dapi](-2), 25 degrees C, mu = 0.1 mol dm(-3)). Cyclic voltammetry established quasi-reversible formation of [Ni(dapi)2]3+ with a redox potential of 0.91 V (versus NHE) for the Ni(II/III) couple. [Co(dapi)2]3+ was prepared by aerial oxidation of the corresponding CoII precursor. The two isomers trans-[Co(dapi)2]3+ (1(3+), 26%) and cis-[Co(dapi)2]3+ (2(3+), 74%), have been separated and isolated as solid Cl- and CF3SO3- salts. In a non-aqueous medium 1(3+) and 2(3+) reacted with paraformaldehyde and NEt3 to give the methylidene-imino derivatives 3(3+) and 4(3+), in which the two piperidine rings are bridged by two or one N-CH2-O-CH2-N bridges, respectively. Crystal structure analyses were performed for H3dapi[ZnCl4]Cl, 1Cl3 x 2H2O, 2Cl3 x H2O, 3[ZnCl4]Cl, 4[ZnCl4]Cl, [Ni(dapi)2]Cl2 x H2O, [Cu(dapi)2](NO3)2, [Cu(dapi)Cl2], [(dapi)ClCd-(mu2-Cl)2-CdCl(dapi)], and [Co(dapi)(NO2)(CO3)]. The stability of [M(II)(dapi)]2+ and [M(II)(dapi)2]2+ complexes in aqueous solution, particularly the remarkably high tendency of [M(dapi)]2+ to undergo coordinative disproportionation is discussed in terms of the specific steric requirements of this ligand. Molecular mechanics calculations have been performed to analyze the different types of strain in these complexes. A variety of alkylated derivatives of dapi have been prepared by reductive alkylation with formaldehyde, benzaldehyde, salicylaldehyde, and pyridine-2-carbaldehyde. The NiII complexes of the pentadentate N3,N5-bis(2-pyridinylmethyl)-cis-3,5-diaminopiperidine (py2dapi) and the hexadentate N3,N5,1-tris(2-pyridinylmethyl)-cis-3,5-diaminopiperidine (py3dapi) have been isolated as crystalline ClO4- salts [Ni(py2dapi)Cl]ClO4 and [Ni(py3dapi)](ClO4)2 x H2O and characterized by crystal structure analyses.     

Isolation of a pentadentate ligand and stepwise synthesis, structures, and magnetic properties of a new family of homo- and heterotrinuclear complexes

A neutral pentadentate ligand, di(pyrazolecarbimido)amine (Hdcadpz), and its adduct with HClO4, [H2dcadpz]+[ClO4]-, were for the first time isolated from our previously reported [Cu3(dcadpz)2(Hpz)2(ClO4)2](ClO4)2.H2O by the use of (NH4)2S to remove the CuII ions and characterized by IR, EA, UV, NMR, MS, and X-ray crystallography. Reactions of copper(II) or nickel(II) nitrate with Hdcadpz in a 1:2 molar ratio generated two mononuclear precursors of [Cu(dcadpz)2] (1) and [Ni(dcadpz)2].2/3DMF (2). Furthermore, three new linear homo- and heterotrinuclear complexes of the same motif [M{M'(dcadpz)2}M] (M=CoII, NiII, M'=CuII, NiII), [{Co(pdm)}2{Cu(dcadpz)2}](NO3)4 (3), [{Ni(pdm)}2{Cu(dcadpz)2}](NO3)4 (4), and [{Ni(MeOH)(H2O)2}2{Ni(dcadpz)2}](NO3)4 (5), were synthesized from these two precursors (pdm=2,6-pyridinedimethanol) and characterized by X-ray crystallography. Magnetic studies show that the central Cu(dcadpz)2 motif is antiferromagnetically coupled with both the terminal Co(II) atoms via the dcadpz- ligand in 3 with a J value of -5.27 cm(-1) and ferromagnetically coupled with both the terminal Ni(II) atoms in 4 with a J value of 2.50 cm(-1), while 5 behaves only as a Curie paramagnet between 2 and 300 K due to the diamagnetic character of the central square-planar Ni(II) atom.     

Tetraamide macrocyclic complexes of transition metals with ligands derived from hydrazine

Succinic acid or phthalic acid react with hydrazine hydrate and formaldehyde in the presence of metal ions to give the macrocyclic complexes [ML1Cl2] or [ML2Cl2][M = FeII, CoII, NiII, CuII and ZnII]. The resulting cyclization has been identified, on the basis of i.r. and 1H-n.m.r. studies. The coordination of amide groups through nitrogen and the overall geometry of the complexes have been assigned on data obtained from elemental analyses i.r., u.v.-vis., magnetic moments, e.p.r and conductivity studies. All the complexes exhibit an octahedral geometry, except copper which is square planar, where the amide group coordinates through nitrogen, and are air stable. The observed low molar conductivity values suggest the non-ionic nature of all the compounds.     

DNA cleavage on photoexposure at the d-d band in ternary copper(II) complexes using red-light laser

Ternary copper(II) complexes [Cu(L1)B](ClO4) (1, 2) and [Cu(L2)B](ClO4) (3, 4), where HL1 and HL2 are tridentate NSO- and ONO-donor Schiff bases and B is a heterocyclic base, viz. dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 1 and 3) or dipyrido[3,2-a:2',3'-c]phenazine (dppz, 2 and 4), were prepared and their DNA binding and photoinduced DNA cleavage activity studied. Complex 1, structurally characterized by single-crystal X-ray crystallography, shows an axially elongated square-pyramidal (4 + 1) coordination geometry in which the monoanionic L1 binds at the equatorial plane. The NN-donor dpq ligand exhibits an axial-equatorial binding mode. The complexes display good binding propensity to calf thymus DNA, giving a relative order 2 (NSO-dppz) > 4 (ONO-dppz) > 1 (NSO-dpq) > 3 (ONO-dpq). They cleave supercoiled pUC19 DNA to its nicked circular form when treated with 3-mercaptopropionic acid (MPA) by formation of hydroxyl radicals as the cleavage active species under dark reaction conditions. The photoinduced DNA cleavage activity of the complexes was investigated using UV radiation of 365 nm and red light of 633, 647.1, and 676.4 nm (CW He-Ne and Ar-Kr mixed gas ion laser sources) in the absence of MPA. Complexes 1 and 2, having photoactive NSO-donor Schiff base and dpq/dppz ligands, show dual photosensitizing effects involving both the photoactive ligands in the ternary structure with significantly better cleavage properties when compared to those of 3 and 4, having only photoactive dpq/dppz ligands. Involvement of singlet oxygen in the light-induced DNA cleavage reactions is proposed. A significant enhancement of the red-light-induced DNA cleavage activity is observed for the dpq and dppz complexes containing the sulfur ligand when compared to their earlier reported phen (1,10-phenanthroline) analogue. Enhancement of the cleavage activity on photoexposure at the d-d band indicates the occurrence of metal-assisted photosensitization processes involving the LMCT and d-d band in the ternary structure.     

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].     

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.     

Metal-assisted red light-induced DNA cleavage by ternary L-methionine copper(II) complexes of planar heterocyclic bases

Ternary copper(II) complexes [Cu(l-met)B(Solv)](ClO4) (1-4), where B is a N,N-donor heterocyclic base like 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 3) and dipyrido[3,2-a:2'],3'-c]phenazene (dppz, 4), are prepared and their DNA binding and photo-induced DNA cleavage activity studied (L-Hmet =L-methionine). Complex 2, structurally characterized by X-ray crystallography, shows a square pyramidal (4 + 1) coordination geometry in which the N,O-donor L-methionine and N,N-donor heterocyclic base bind at the basal plane and a solvent molecule is coordinated at the axial site. The complexes display a d-d band at approximately 600 nm in DMF and exhibit a cyclic voltammetric response due to the Cu(II)/Cu(I) couple near -0.1 V in DMF-Tris-HCl buffer. The complexes display significant binding propensity to the calf thymus DNA in the order: 4(dppz) > 3(dpq) > 2(phen> 1(bpy). Control cleavage experiments using pUC19 supercoiled DNA and distamycin suggest major groove binding for the dppz and minor groove binding for the other complexes. Complexes 2-4 show efficient DNA cleavage activity on UV (365 nm) or red light (632.8 nm) irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. The DNA cleavage activity of the dpq complex is found to be significantly more than its dppz and phen 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...     

Complexes of cyclocarbohydroxamic acids with cobalt(II), nickel(II) and copper(II)

A spectroscopic investigation of the reactions of cyclopropanecarbohydroxamic acid (CPAH) with CoII and of cyclohexylacetohydroxamic acid (CHAH) with CoII, NiII and CuII in aqueous solution reveals the sole formation 1:2 complexes at equilibrium. Stability constants (log2 at 25°C and I=0.1 mol dm–3) are 9.11, 9.91, 11.70 and 24.18 for [Co(CPA)2], [Co(CHA)2], [Ni(CHA)2] and [Cu(CHA)2], respectively. Spectral and magnetic studies of the isolated complexes indicate octahedral coordination via the oxygen atoms of the hydroxamate group for the CoII and NiII complexes but a square planar geometry for the CuII complex.     

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.     

Tuning the selectivity/specificity of fluorescent metal ion sensors based on N2S2 pyridine-containing macrocyclic ligands by changing the fluorogenic subunit: spectrofluorimetric and metal ion binding studies

Two new fluorescent chemosensors for metal ions have been synthesized and characterized, and their photophysical properties have been explored; they are the macrocycles 5-(2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L5) and 5-(5-chloro-8-hydroxyquinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L6). Both systems have a pyridyl-thioether-containing 12-membered macrocycle as a binding site. The coordination properties of these two ligands toward CuII, ZnII, CdII, HgII, and PbII have been studied in MeCN/H2O (1:1 v/v) and MeCN solutions and in the solid state. The stoichiometry of the species formed at 25 degrees C have been determined from absorption, fluorescence, and potentiometric titrations. The complexes [CuL5](ClO4)(2).1/2MeCN, [ZnL5(H2O)](ClO4)2, [HgL5(MeCN)](ClO4)2, [PbL5(ClO4)2], [Cu3(5-Cl-8-HDQH-1)(L6H-1)2](ClO4)(3).7.5H2O (HDQ=hydroxyquinoline), and [Cu(L6)2](BF4)(2).2MeNO2 have also been characterized by X-ray crystallography. A specific CHEF-type response of L5 and L6 to the presence of ZnII and CdII, respectively, has been observed at about pH 7.0 in MeCN/H2O (1:1 v/v) solutions.     

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.     

Mono and trinuclear complexes of alpha-oximinoacetoacetylpyridine-4-phenylthiosemicarbazone

Complexes of several transition metal ions with alpha-oximinoacetoacetyl pyridine-4-phenylthiosemicarbazone (H3OAPT) have been prepared. Attempts were made to elucidate their geometries by elemental analysis, molar conductance, magnetic measurements and by some spectroscopic (IR, ESR and electronic) techniques. All the investigated metal ions form mononuclear complexes except for CuII, which forms mononuclear and trinuclear complexes with its chloride and acetate salts, respectively. The IR spectra show that the ligand behaves as a mono or binegative tridentate. Moreover, it acts as a trinegative hexadentate in the trinuclear CuII complex. The protonation constants (logK1H = 9.9 and log K2H = 6.0), as well as the stability constants of the metal complexes, are determined by the pH-titration of H3OAPT and its metal(II) complexes against 0.01 M NaOH. CuII complexes possess square-planar stereochemistry while CoII and NiII have an octahedral one. The crystal field parameters of CoII and NiII complexes are evaluated.     

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.     

Metal-assisted esterification: glutaric acid-iron(II) complexes in the gas phase

Transition metal ions are routinely used to assist organic reactions; however, direct detection of the intermediates in such reactions is uncommon. Here, we demonstrate a transition metal ion-assisted reaction between glutaric acid (L) and methanol, using electrospray ionization mass spectrometry (ESI-MS). Esterification of glutaric acid does not occur in aqueous methanol solution under ESI conditions, but the FeII-bound acid cluster, [FeII L2 - H]+, adds methanol and dehydrates to give rise to an abundant product ion with a 14 Da increased mass. The occurrence of methyl esterification is supported by collision-induced dissociation and isotopic labeling data, which indicate that the sequence by which the product ion is generated is loss of water, followed by the addition of methanol. Electrospray ionization conditions, specifically the tube lens offset voltage, strongly affect the reaction efficiency, presumably through control of the dehydration process. Other transition metal ions, such as NiII, ZnII, CoII and CuII, also show distinctive metal-assisted reactions.     

Tetranuclear CoII, MnII, and CuII complexes of a novel binucleating pyrazolate ligand preorganized for the self-assembly of compact [2 x 2]-grid structures

A straightforward synthesis toward the preparation of the rigid pyrazolate ligand L(H) featuring bipyridyl side-arms is described, starting from 2,2'-bipyridyl-N-oxide as the sole organic building block. In this context, optimized procedures for the synthesis of the organic intermediates 6-acetyl-2,2'-bipyridine 1 and 6-methylcarboxy-2,2'-bipyridine 2 are reported. The new ligand comprises two proximate terpyridine-like binding sites and is shown to form discrete [2 x 2]-grid complexes with CoII, MnII, and CuII in a highly selective self-assembly process, even in the presence of excess metal precursor. The thus obtained complexes [Co4L4][Na(NO3)4](NO3) (3), [Mn4L4](PF6)4 (4), and [Cu4L4](ClO4)4 (5) are fully characterized, including X-ray crystallographic analyses, and their magnetic properties are discussed. All three complexes show weak to moderate antiferromagnetic coupling between the four nuclei. The stability of the grid structures proved very high, as dissociation or exchange between metal ions in solution was not observed in a set of competition experiments.