Substitution behaviour of novel dinuclear Pt(II) complexes with bio-relevant nucleophiles

The novel dinuclear Pt(II) complexes [{trans-Pt(NH(3))(2)Cl}(2)(μ-pyrazine)](ClO(4))(2) (Pt1), [{trans-Pt(NH(3))(2)Cl}(2)(μ-4,4'-bipyridyl)](ClO(4))(2)·DMF (Pt2), and [{trans-Pt(NH(3))(2)Cl}(2)(μ-1,2-bis(4-pyridyl)ethane)](ClO(4))(2) (Pt3), were synthesized. Acid-base titrations, and temperature and concentration dependent kinetic measurements of the reactions with biologically relevant ligands such as thiourea (Tu), glutathione (GSH) and guanosine-5'-monophosphate (5'-GMP) were studied at pH 2.5 and 7.2. The reactions were followed under pseudo-first-order conditions by stopped-flow and UV-vis spectrophotometry. (1)H NMR spectroscopy was used to follow the substitution of chloride in the complex [{trans-Pt(NH(3))(2)Cl}(2)(μ-4,4'-bipyridyl)](ClO(4))(2)·DMF by guanosine-5'-monophosphate (5'-GMP) under second-order conditions. The results indicate that the bridging ligand has an influence on the reactivity of the complexes towards nucleophiles. The order of reactivity of the investigated complexes is Pt1 > Pt2 > Pt3.     

Substitution behaviour of amine-bridged dinuclear Pt(II) complexes with bio-relevant nucleophiles

Complexes of the type [Pt2(N,N,N',N'-tetrakis(2-pyridylmethyl)diamine(HO)2]4+ and [Pt2(N,N,N',N'-tetrakis(2-pyridylmethyl)diamine(Cl)2]2+ were used to study their reactions with a series of bio-relevant nucleophiles, viz. thiourea, L-methionine and guanosine-5'-monophosphate (5'-GMP2-) as a function of nucleophile concentration and temperature. The reactions with the sulfur containing nucleophiles (thiourea and L-methionine) were followed under pseudo-first-order conditions by stopped-flow and UV-Vis spectrophotometry. The reaction with 5'-GMP2- was carried out under second order conditions and studied by NMR spectroscopy. The results indicate that the bridged dinuclear complexes remain intact after coordination of the studied nucleophiles for an extended period of time, which differs significantly from that reported for other multinuclear platinum complexes in the literature.     

Electronic spectra of Cu(II) crystal complexes with S-methylthiosemicarbazones

Electronic spectra for a series of coordination compounds of copper(II) with tridentant ligands of salicyl aldehyde S-methylthiosemicarbazone and 8-quinoline aldehyde S-methylthiosemicarbazone were investigated. Coordinations of central ions were determined on the basis of X-ray data and IR spectra. Electronic transitions were detected by processing the diffusion-reflection spectra according to theKubelka-Munk theory. Identifications proved the presence of bands corresponding to intraligand transition, charge transfer spectra and the transition of d-d type which are the result of the elimination of d-orbital degeneration for Cu(II) ions in the crystal field. The effect of the symmetry of coordination polyhedrons is discussed.

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Elektronenspektren von Cu(II) Kristall-Komplexen mit S-Methylthiosemicarbazonen

Zusammenfassung Es wurden Elektronenspektren einer Serie von Koordinationsverbindungen des Kupfer(II) mit tridentaten Liganden (Salizylaldehyd-S-methylthiosemicarbazon und 8-Chinolinylaldehyd-S-methylthiosemicarbazon) untersucht. Die Zentralionkoordination wurde durch Röntgenstrahlenuntersuchungen und auf Grund der IR-Spektren festgestellt. Die Elektronenübergänge wurden nach derKubelka-Munk-Theorie aus den diffusen Reflexionsspektren ermittelt. Die Banden wurden den Intraligandübergängen, dem charge-transfer-Spektrum und den d-d-Typ-Übergängen, die als Resultat der Entartungsbeseitigung der Cu(II)-d-Orbitale im Kristallfeld verschiedener Symmetrie entstehen, zugeschrieben.

     

Spectroscopic evaluation of Co(II), Ni(II) and Cu(II) complexes derived from thiosemicarbazone and semicarbazone

Co(II), Ni(II) and Cu(II) complexes were synthesized with thiosemicarbazone (L(1)) and semicarbazone (L(2)) derived from 2-acetyl furan. These complexes were characterized by elemental analysis, molar conductance, magnetic moment, mass, IR, electronic and EPR spectral studies. The molar conductance measurement of the complexes in DMSO corresponds to non-electrolytic nature. All the complexes are of high-spin type. On the basis of different spectral studies six coordinated geometry may be assigned for all the complexes except Co(L)(2)(SO(4)) and Cu(L)(2)(SO(4)) [where L=L(1) and L(2)] which are of five coordinated square pyramidal geometry.     

Three new polynuclear tetracarboxylato-bridged copper(II) complexes: Syntheses, X-ray structure and magnetic properties

The synthesis, crystal structure and magnetic measurements of three new polynuclear tetracarboxylato-bridged copper(II) complexes, i.e. {[Cu₄(phen)₂(μ-O₂CC₂H₅)₈] · (H₂O)}_n (1), [Cu₂(μ-O₂CC₆H₄OH)₄(C₇H₇NO)₂] · 6H₂O (2) and [Cu₂(μ-O₂CCH₃)₄(C₇H₇NO)₂] (3) (phen = 1,10-phenanthroline, O₂CC₆H₄OH = 3-hydroxy benzoate, C₇H₇NO = 4-acetylpyridine) are reported. All compounds consist of dinuclear units, in which two Cu(II) ions are bridged by four syn,syn-η¹:η¹:μ carboxylates, showing a paddle-wheel cage type with a square-pyramidal geometry, arranged in different ways. The structure of compound 1 consists of an one-dimensional structure generated by an alternating classical dinuclear paddle-wheel unit and an unusual dinuclear Cu₂(μ-OCOC₂H₅)₂(μ-O₂CC₂H₅)₂(phen)₂unit, which are connected to each other via a syn,anti-triatomic propionato bridge in an axial-equatorial configuration. The adjacent chains are connected to generate a 2D structure through the face-to-face π–π interaction between phen rings. Structures of compounds 2 and 3 both consist of a symmetric dinuclear Cu(II) carboxylate paddle-wheel core and pyridyl nitrogen atoms of 4-acetylpyridine ligand at the apical position, and just differ in the substituents of the equatorial ligands.

The magnetic properties have been measured and correlated with the molecular structures. It is found that in the two classical paddle-wheel compounds the Cu(II) ions are strongly antiferromagnetically coupled with J = −278.5 and −287.0 cm⁻¹ for complexes 2 and 3, respectively. In compound 1 the magnetic susceptibility could be fitted with two different, independent Cu(II) units, one strongly coupled and one weakly coupled; the paddle-wheel dinuclear unit has the strongest antiferromagetic coupling with a value for J of −299.5 cm⁻¹, whereas the Cu(II) ions in the propionato-bridged dinuclear unit of 1 display a very weak antiferromagnetic coupling with a value for J = −0.75 cm⁻¹, due to the orthogonality of the magnetic orbitals. Also the exchange within the chain is therefore very weak. The magneto-structural correlations for complexes 1, 2, and 3 are discussed on the basis of the structural parameters and magnetic data for the complexes.     

Complexes of Co(II), Ni(II) and Cu(II) with lapachol

Complexes of naturally occurring hydroxynaphtho-quinone, lapachol (2-hydroxy-3(3-methyl-2-buthenyl)-1,4-naphthoquinone = HL) with Co(II), Ni(II) and Cu(II) have been prepared by reaction of the corresponding acetates with the ligand (HL) in ethanol. The molecular and crystal structures were determined for [CoL₂(EtOH)₂] (1), [NiL₂(EtOH)₂] (2), and [CuL₂(py)₂] (3). In all cases the deprotonated lapachol behaves as chelating bidentate ligand. The complexes were also characterized by elemental analyses, cyclic voltammetry, and FAB-MS.     

Hydrothermal syntheses,crystal structures and antibacterial activities of two Cu(II) complexes with quinolones

Hydrothermal reactions of ciprofloxacin with Cu(ClO₄)₂?·?6H₂O, and ofloxacin with Cu(CH₃COO)₂?·?4H₂O, yield two metal complexes: [Cu(H-Cip)₂]?·?(ClO₄)₂?·?6H₂O (1) and [Cu(Ofl)₂?·?H₂O]?·?2H₂O (2), which were characterized by elemental analysis, IR and single crystal diffraction analyses. Compounds 1 and 2 were screened for antibacterial activities against Staphylococcus aureus, Escherichia coli, Candida albicans and pseudomonas aeruginosa.     

EPR, IR and electronic spectral studies on Ni(II) and Cu(II) complexes with N-donor tetradentate [N4] macrocyclic ligand

Nickel(II) and copper(II) complexes are synthesized with a novel tetradentate macrocyclic ligand, i.e. 2,6,12,16,21,22-hexaaza;3,5,13,15-tetraphenyltricyclo[15,3,1,1(7-11)] docosa;1(21),2,5,7,9,11(22),12,15,17,19-decaene (L) and characterized by the elemental analysis, magnetic susceptibility measurements, mass, (1)H NMR, IR, electronic and EPR spectral studies. All the complexes are non-electrolytic in nature. Thus, these may be formulated as [M(L)X(2)] [M=Ni(II), Cu(II) and X=Cl(-), NO(3)(-) and (1/2)SO(4)(2-)]. Ni(II) and Cu(II) complexes show magnetic moments corresponding to two and one unpaired electron, respectively. On the basis of IR, electronic and EPR spectral studies an octahedral geometry has been assigned for Ni(II) and tetragonal geometry for Cu(II) complexes.     

Spectrophotometric study of coproporphyrin-I complexes of copper(II) and cobalt(II)

The reagent 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) was used for the spectrophotometric determination of copper(II) and cobalt(II) in the presence of pyridine and imidazole catalysts. Optimum conditions were investigated and the methods were applied to the determination of parts per billion levels of copper(II) and cobalt(II). The Sandell sensitivities of the recommended procedures were 0.568 μm cm⁻² and 0.464 μg cm⁻² (for A = 0.001) for copper and cobalt, respectively. The relative standard deviations were 2.0% for copper and 1.0% for cobalt. The kinetics of the reaction of CPI with copper(II) and cobalt(II) in the presence of the catalysts and the influence of the temperature were studied, and their kinetic constants determined.The influence of light on the photodecomposition of CPI was also studied.     

Synthesis and characterization of Cu(II) complexes of pyrazine-2,3-dicarboxylicacid

Four copper(II) coordination polymers, {[Cu(pz(COO)₂)(H₂O)]₄·HBr}_n (1), {[Cu(pz(COO)₂)(NH₃)₂]·H₂O}_n (2), {[Cu₃H₂(pz(COO)₂)₄(H₂O)₃]·2H₂O}_n (3) and {[Cu₂(pz(COO)₂)₂(NH₃)₂(H₂O)₃][Cu(pz(COO)₂)(NH₃)(H₂O)₂][Cu(pz(COO)₂)(NH₃)(H₂O)]·2H₂O}_n (4) were synthesized using pyrazine-2,3-dicarboxylic acid, CuBr₂, 2-(2-aminoethylamino)ethanol/triethanol amine/ammonia in a methanol:water (1:1) solution, and the mixed ligand complexes were characterized by spectroscopic methods, thermal and elemental analysis, and magnetic susceptibility. Complexes 2 and 4 were also characterized by means of single crystal X-ray crystallography. The characterizations show that the complexes have polynuclear molecular structures, except for complex 2, and all of the complex structures form polymeric chains. Complex 4 has a pseudo-merohedral twin structure.     

Heterobinuclear and Heterotrinuclear complexes of Oxorhenium(V) with Cu(II), Ni(II), Fe(III), UO2(VI) and Th(IV) in the solid state

New heteronuclear complexes containing oxorhenium(V), Cu(II), Ni(II), Fe(III), UO₂(VI) and Th(IV) ions were prepared by the reaction of the complex ligand, [ReO(H₄L)Cl]Cl₂, where H₄L = 8,17-dimethyl-6,15-dioxo-5,7,14,16-tetrahydrodibenzo[a,h][14]annulene-2,11-dicarboxylic acid, with the previous transition and actinide salts. Three heteronuclear Cu(II) complexes were isolated depending on the ratio of [ReO(H₄L)Cl]Cl₂?:?Cu(II) ion. When the ratios were 1?:?0.5, 1?:?1 and 1?:?2, the heteronuclear complexes {[ReO(H₃L)Cl]₂CuCl₂(OH₂)₂}SO₄ · H₂O (I), [ReO(H₃L)Cl₂Cu(OH₂)₂(SO₄)] (II) and {ReO(H₂L)Cl[Cu(OH₂)₃ SO₄]₂} (III) were obtained, respectively. Heteronuclear complexes of the other metal cations were obtained by mixing [ReO(H₄L)Cl]Cl₂ with the metal salt in the ratio 1?:?1 to obtain the heteronuclear complexes [ReO(H₃L)Cl₂Ni(OH₂)₂](NO₃)₂ (IV), [ReO(H₃L)Cl₃Fe(OH₂)₃](NO₃)₂ (V), [ReO(H₃L)ClUO₂(NO₃)₂ (OH₂)]Cl (VI) and [ReO(H₃L)Cl₃Th(NO₃)₂(OH₂)]NO₃ · 2H₂O (VII). The complex ligand coordinates with the heterometal ion via the carboxylate group, and the infrared bands ν_as COO and ν_s COO indicate that the carboxylate acts as a unidentate ligand to the heterometal cations. Cu(II) and Fe(III) cations in the heteronuclear complexes have octahedral geometry, while Ni(II) is square planar. Thermal studies explored the possibility of obtaining new heteronuclear complexes pyrolytically in the solid state from the corresponding mother complexes. The structures of the complexes were elucidated by conductance, IR and electronic spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy.     

Nickel(II) and copper(II) complexes of unsymmetrical tetradentate reduced Schiff base ligands

Two new reduced Schiff base ligands, [HL¹ = 4-{2-[(pyridin-2-ylmethyl)-amino]-ethylimino}-pentan-2-one and HL² = 4-[2-(1-pyridin-2-yl-ethylamino)-ethylimino]-pentan-2-one] have been prepared by reduction of the corresponding tetradentate unsymmetrical Schiff bases derived from 1:1: 1 condensation of 1,2-ethanediamine, acetylacetone and pyridine-2-carboxaldehyde/2-acetyl pyridine. Four complexes, [Ni(L¹)]ClO₄ (1), [Cu(L¹)]ClO₄ (2), [Ni(L²)]ClO₄ (3), and [Cu(L²)]ClO₄ (4) with these two reduced Schiff base ligands have been synthesized and structurally characterized by X-ray crystallography. The mono-negative ligands L¹ and L² are chelated in all four complexes through the four donor atoms to form square planar nickel(II) and copper(II) complexes. Structures of 3 and 4 reveal that enantiomeric pairs are crystallized together with opposite chirality in the nitrogen and carbon atoms. The two Cu^II complexes (2 and 4) exhibit both irreversible reductive (Cu^II/Cu^I; E_pc, −1.00 and −1.04 V) and oxidative (Cu^II/Cu^III; E_pa, +1.22 and +1.17 V, respectively) responses in cyclic voltammetry. The electrochemically generated Cu^I species for both the complexes are unstable and undergo disproportionation.     

Polarized spectroscopy and hybrid materials of chiral Schiff base Ni(II), Cu(II), Zn(II) complexes with included or separated azo-groups

Chiral Schiff base complexes containing azo-groups, bis(N-R-1-naphtylethyl-4-phenyldiazenylsalicydenaminato) nickel(II), copper(II), and zinc(II) complexes affording a distorted square planar trans-[MN₂O₂] coordination geometry were prepared newly. Organic/inorganic hybrid materials in polymethylmethacrylate (PMMA) cast films of them (a containing type) or the analogous chiral Schiff base complexes, bis(N-R-1-phenylethyl-3,5-dichlorosalicydenaminato) nickel(II), copper(II), and zinc(II), and azobenzene (AZ) (a separated type) were assembled for comparison of polarized UV light induced molecular arrangement caused by Weigert effect. Investigation of parameters for optical anisotropy of metal complexes as well as AZ suggested that the degree of increasing optical anisotropy of the containing type is higher than that of the separated type based on π-π^∗ (of which characteristic band appeared around 380 nm), n-π^∗, and d-d bands of polarized absorption electronic spectra. Rigid nickel(II) or zinc(II) complexes are easy to increase optical anisotropy than flexible copper(II) complexes for both types.     

Synthesis of new Cu(II), Ni(II) and Co(II) complexes with a bis-amide ligand functionalized with pyridine moieties: Spectral, magnetic and electrochemical studies

Three new copper(II), nickel(II) and cobalt (II) dinuclear complexes with a bis-amide ligand derived from tartaric acid have been prepared and characterized. For this purpose, the ligand (R,R)-(+)-di-N,N′-methylpyridino-tartramide (dmpt) was synthesized via the classical aminolysis of (R,R)-(+)-dimethyltartrate with pyridylmethylamine. The molecular structures of the complexes Na[Cu₂(dmptH₋₃)(CO₃)] · 8H₂O (1) and [Ni₂(dmptH₋₂)₂] · 9.75H₂O (2) were elucidated by X-ray diffraction, and the complex [Co₂(dmptH₋₃)(μ-OH)] · NaClO₄ · 5H₂O (3) by XAS. The crystal structure of (1) shows that the two metallic centres are in a square planar environment. Each copper(II) is bound to pyridyl and deprotonated amidic nitrogen atoms and to the oxygen atoms of hydroxyl and carbonato groups. In complex (2), both nickel atoms are in a distorted octahedral environment with an identical set of donors atoms, N₄O₂, coming from four nitrogen atoms of two pyridylmethylamido moieties and two oxygen donor atoms of alcohol groups. XAS analysis of complex (3) allows us to propose a CoN₂O₄ chromophore, with two nitrogen atoms coming from pyridyl and amidic groups and two bridged oxygen atoms from a deprotonated alcohol group and an hydroxyl group; the hexacoordination is achieved by two water molecules. The spectroscopic, electrochemical and magnetic properties of these complexes were investigated.     

Synthesis and Characterization of A Vic-Dioxime Derivative and Investigation of its Complexes with Ni(II), Co(II), Cu(II) and UO2(VI) Metals

In this study, 1,2-dihdroxyimino-3,7-di-aza-9,10-O-iso-propylidene decane (LH₂ ) was synthesized starting from 1,2-O-iso-propylidene-4-aza-7-aminoheptane (RNH₂ ) and anti-chloroglyoxime. Complexes of this ligand with Ni(II), Co(II), Cu(II) and UO₂(VI) salts were prepared. Structures of the ligand and its complexes are proposed based on elemental analyses, IR, ¹³C and ¹H NMR spectra magnetic susceptibility measurements and thermogravimetric analyses (TGA).     

The role of chiral dopants in organic/inorganic hybrid materials containing chiral Schiff base Ni(II), Cu(II) and Zn(II) complexes

Chiral Schiff base complexes containing azo-groups, bis(N-R-1-cyclohexylethyl-4-phenyldiazenylsalicydenaminato) nickel(II), copper(II) and zinc(II) complexes, and without azo-groups, bis(N-R-1-cyclohexylethyl-3,5-dichlorosalicydenaminato) nickel(II), copper(II) and zinc(II) complexes, affording a distorted square planar trans-[MN₂O₂] coordination geometry were prepared. Organic/inorganic hybrid materials in polymethylmethacrylate (PMMA) spincoat films of the complexes (both the azobenzene (AZ) containing type and the latter complexes of the AZ separated type) were assembled for a comparison of polarized UV light induced molecular arrangement caused by the Weigert effect. Investigation of the parameters for the optical anisotropy of the metal complexes as well as AZ suggested that the degree of increasing optical anisotropy of the containing type was higher than that of the separated type based on π-π^∗ (of which a characteristic band appeared around 380 nm) and n-π^∗ bands of polarized absorption electronic spectra. In the AZ containing type, the rigid nickel(II) or zinc(II) complexes easily increase the optical anisotropy compared to the flexible copper(II) complexes. In the AZ separated type, interestingly, enhancement of some CD bands suggests the role of chiral dopants of some complexes without azo-groups for AZ.     

Ligand assembly and metal ion complexation: syntheses and X-ray structures of Ni(II) and Cu(II) benzoate and 4-tert-butylbenzoate complexes of cyclam

The syntheses and X-ray structures of trans-[Ni(O-benzoato)₂(cyclam)], trans-[Cu(H₂O)₂(cyclam)]-(benzoate)₂·2H₂O and trans-[Cu(H₂O)₂(cyclam)](4-t-butyl-benzoate)₂ (where cyclam is 1,4,8,11-tetraazacyclotetradecane) are described. The nickel complex has a tetragonally distorted octahedral coordination geometry with cyclam occupying the equatorial plane in a stable trans-III arrangement, with benzoate ligands filling the axial positions. The structure closely resembles the arrangement in the previously described hydrogen-bonded (metal-free) ligand assembly [(cyclamH₂)·(4-t-butyl benzoate)₂]·2(benzoic acid) if the latter benzoic acid moieties, which do not interact directly with the cyclam moiety, are ignored. The 2?:?1 fragment thus may be viewed as a ligand assembly “preorganized” for nickel ion complexation. In contrast to the nickel structure, the two trans-axial sites in both copper structures are occupied by aqua rather than O-carboxylate ligands. Although they do not form part of the inner coordination sphere in either complex, the two carboxylate anions remain hydrogen bound to the (coordinated) cyclam ligand, with the mode of packing being generally similar in each complex.     

Spectral,magnetic, biological,and thermal studies of metal(II) complexes of some unsymmetrical Schiff bases

New nickel(II) and copper(II) complexes with unsymmetrical Schiff bases derived from aromatic 2-hydroxy aldehydes were synthesized and characterized by elemental analyses, melting points, ¹H-NMR, magnetic susceptibility, thermogravimetric analysis, differential scanning calorimetry (DSC), infrared (IR), and electronic spectral measurements. Comparison of IR spectra of the Schiff bases and their metal complexes indicated that the Schiff bases are tetradentate, coordinated via the two azomethine nitrogens and the two phenolic oxygens. Magnetic moments and electronic spectral data confirm square-planar geometry for the complexes. Thermal studies reveal a general decomposition pattern, whereby the complexes decomposed partially in a single step due to loss of part of the organic moiety. A single endothermic profile, corresponding to melting point, was observed from the DSC of all complexes, except those whose ligand contained the nitro group, which decomposed exothermally without melting. The Schiff bases and their complexes were screened in vitro against 10 human pathogenic bacteria. The metal(II) complexes exhibited higher antibacterial activity than their corresponding Schiff bases.     

Steric effect on construction of Cu(II) complexes with pyridine carboxamide ligands

The structures of three new Cu(II) complexes with pyridine carboxamide ligands (Me₂bpb, 6-Me₂-Mebpb, and 6-Me₂-Me₂bpb) have been determined. 6-Methyl-substituted pyridyl bpb ligands produced dimeric compounds with Cu(II) ions, and weak interactions between dimers can make even polymeric compounds, while bpb ligands without 6-methyl substitution produced monomeric Cu(II) complexes. The large distortion effects of 6-methyl-substitution are shown in Cu(II) complexes with 6-methyl-substituted pyridyl bpb ligands. This result suggests that the steric effect of 6-methyl-substitution plays important role for distortion of the structure, and 6-methyl-substitution can also influence to make polymeric compounds with interactions between Cu(II) ions and neighbor carbonyl oxygen atoms. In addition, the voltammetric behaviors of the Cu complexes were examined and classified into two groups, with/without 6-methyl group. The complexes without 6-methyl group show reversible redox waves at −1.6 V, and the complexes with 6-methyl group do irreversible redox ones at −1.3 V, indicating that the presence of the methyl group of 6-position of the complex makes the reduction of the complexes easier.