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.     

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...     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

New macrocyclic complexes containing amide,imine and secondary amine functions

New double-ring octa-aza macrocyclic complexes, synthesized by condensation of oxamide-N,N-diethanoic acid with diethylenetriamine in 1:2 ratio in the presence of CuII, NiII or CoII, have been characterized by elemental analyses, i.r., u.v., magnetic susceptibility and conductivity measurements. The complexes are non-electrolytes, in which each metal ion is in a spin-free state in a pseudo- octahedral geometry. The high magnetic moments are attributed to a ferromagnetic effect.     

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.     

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 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.     

Thiosalicylic acid-immobilized Amberlite XAD-2: metal sorption behaviour and applications in estimation of metal ions by flame atomic absorption spectrometry

Thiosalicylic acid (TSA)-modified Amberlite XAD-2 (AXAD-2) was synthesized by coupling TSA with the support matrix AXAD-2 through an azo spacer. The resulting chelating resin was characterized by elemental analyses, thermogravimetric analysis (TGA) and infrared spectra. The newly designed resin quantitatively sorbs CdII, CoII, CuII, FeIII, NiII and ZnII at pH 3.5-7.0 when the flow rate is maintained between 2 and 4 ml min-1. The HCl or HNO3 (2 mol l-1) instantaneously elutes all the metal ions. The sorption capacity is 197.5, 106.9, 214.0, 66.2, 309.9 and 47.4 mumol g-1 of the resin for cadmium, cobalt, copper, iron, nickel and zinc, respectively, whereas their preconcentration factor is between 180-400. The breakthrough volume of HCl or HNO3 for elution of these metal ions was found to be 4-8 ml. The limit of detection (LOD) for CdII, CoII, CuII, FeIII, NiII and ZnII was 0.48, 0.20, 4.05, 0.98, 1.28 and 3.94 micrograms l-1, respectively, and the limit of quantification (LOQ) was found to be 0.51, 0.29, 4.49, 1.43, 1.58 and 4.46 micrograms l-1, respectively. The loading half time, t1/2, for the cations was found to be less than 2.0 min, except for nickel for which the value was 13.1 min. The determination of each of these six cations is possible in the presence of other five, if their concentration is up to 4 times. All six metals were determined in river water (RSD approximately 0.7-7.7%) and tap water samples (RSD approximately 0.3-5.7%). The estimation of Co was made in the samples of multivitamin tablets (RSD < 2.3%). The results agree with those quoted by manufacturers.     

Metal ion directed synthesis of 14–16 membered tetraimine macrocyclic complexes

A new series of 14–16 membered tetraazatetraimine macrocyclic complexes [ML1X2]-[ML3X2] [M=CoII, NiII and ZnII] and [CuL1]X2-[CuL3]X2 [X=Cl or NO3] have been synthesized by the template condensation of dibenzoylmethane with primary diamines in MeOH. The complexes were characterized by elemental analysis, i.r, 1H-n.m.r., e.p.r. and u.v-vis spectroscopy, as well as by conductivity and magnetic susceptibility measurements. The copper complexes exhibit square planar geometry, whereas an octahedral geometry is suggested for all other complexes.     

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.     

Complexes of 2-furaldehyde 4-phenyl semicarbazone

The synthesis of Co^II, Ni^II, Cu^II and Cd^II complexes of 2-furfural 4-phenyl semicarbazone (FPSC) with stoichiometric formulae: [M(FPSC)₂X₂] (M = Co, Ni or Cu; X = Cl or Br), [CuCl₂(FPSC)] and [(CdCl₂)₂(FPSC)] has been obtained for the first time. The complexes were characterized by elemental analysis, molar conductivity, magnetic measurements, i.r., far i.r. and electronic spectra. FPSC is deduced to act as a bidentate ligand in the Co^II, Ni^II and Cu^II complexes and as a tetradentate one in [(CdCl₂)₂(FPSC)].     

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...