Showing papers in "Transition Metal Chemistry in 2005"

Synthesis, characterization and biological evaluation of manganese(II), cobalt(II), nickel(II), copper(II), and cadmium(II) complexes with monobasic (NO) and neutral (NN) Schiff bases

Abstract: New complexes of MnII, CoII, NiII, CuII, and CdII with bis(acetophenone) ethylenediamine and 5-chlorosalicylideneaniline or 5-bromosalicylideneaniline have been prepared and characterized on the basis of elemental analyses, thermogravimetric analyses, magnetic measurements, electronic and i.r. spectra. The antimicrobial activities of the complexes, ligands, control (dimethyl formamide) and metal salts were tested against Salmonella typhi (bacteria), Saccharomyces cerevisae (yeast), and two fungal species Lasiodiplodia theobromae and Fusarium oxysporum. The results are discussed.

Ruthenium(II) N -heterocyclic Carbene Complexes in the Transfer Hydrogenation of Ketones

Abstract: Six ruthenium-N-heterocyclic carbene complexes (2–7) have been prepared and the new compounds characterized by C, H, N analyses, 1H-n.m.r. and 13C-n.m.r. The reduction of ketones to alcohols via transfer hydrogenation was achieved with catalytic amounts of complexes (2–7) in the presence of t-BuOK.

Palladium(II) Schiff base complexes derived from sulfanilamides and aminobenzothiazoles

Abstract: Schiff bases (HL) derived from sulfanilamides or aminobenzothiazoles add to Pd(OAc)2 to give complexes of the type PdL2 (1–7) in moderate to excellent yields. Reactions of Schiff bases containing pyrimidine groups, however, gave several products arising from competing coordination of the pyrimidine nitrogen. Palladium complexes and Schiff bases have been investigated as antifungal agents against Aspergillus niger and Aspergillus flavus.

Synthesis and characterization of cobalt(II), nickel(II), copper(II), palladium(II) and dioxouranium(VI) complexes of the antipyrine schiff base of 3-formylsalicylic acid

Abstract: A new Schiff base has been synthesized from 4-aminoantipyrine and 3-formylsalicylic acid. The ligand has a dianionic tetradentate compartmental OONO donor system. The cobalt(II), nickel(II), copper(II) and dioxouranium(VI) complexes exist in phenolato-bridged dinuclear species, while palladium(II) gives a mononuclear complex with free –COOH groups. The complexes have been characterized by elemental analyses, i.r., u.v.-vis, thermal and magnetic measurements.

Synthesis, Characterization and DNA-binding Properties of Three 3d Transition Metal Complexes of the Schiff Base Derived from Diethenetriamine with PMBP

Abstract: A new ligand H2L, 1,7-di(1-phenyl-3-methyl-5-pyrazolone-4-benzylidene)diethenetriamine and its three transition metal complexes, ML · nH2O [M=Cu(II), n=2; M=Zn(II), n=0.5; M=Ni(II) (1), n=3] have been synthesized in anhydrous EtOH and characterized on the basis of elemental analyses, molar conductivities, i.r. spectra, u.v. spectra and thermal analyses. In addition, the DNA-binding properties of the ligand and its complexes have been investigated by absorption, fluorescence and viscosity measurements. The experimental results indicated that the ligand and the complex (1) can bind to DNA , but the other two complexes can’t; the binding affinity of the complex (1) is higher than that of the ligand and the intrinsic binding constant kb of the complex (1) is 7.893×105 m−1.

Synthesis and Antibacterial Activity of Ceftriaxone Metal Complexes

Abstract: Ceftriaxone (H2ceftria) interacts with transition metal(II) ions to give [M(ceftria)] complexes (M=Mn, Co, Cu and Cd) and [Fe(ceftria)Cl] which were characterized by physicochemical and spectroscopic methods. Their spectra indicated that the ligand is probably acting as a dianionic pentadentate N2O3 chelating agent. The complexes have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of ceftriaxone.

Study on the interaction of platinum(IV), gold(III) and silver(I) ions with DNA

Abstract: Fluorescence, absorption spectra have been produced by the interaction of platinum(IV), silver(I) and gold(III) ions with the berberine–DNA system (berberine, Scheme 1). Platinum(IV) and gold(III) ions show different effects from that of silver(I) ion on the spectral characteristics of the berberine–DNA system. Quenching fluorescence is seen with platinum(IV) and gold(III) ions addition, whereas increasing fluorescence is observed for silver(I) ions. The addition of gold(III) and silver(I) ions cause an increase in absorption of the berberine–DNA system. The above results suggest that different metal ions exhibit different affinities when binding to DNA correlates well with the ions’ charge, structure and the coordination ability.

Coordination modes of diphosphines in silver(I)-diphosphine complexes mediated by 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz)

Abstract: Silver (I) complexes [Ag2(tptz)(dppm)2(DMF)](BF4)2·2DMF (1), [Ag(tptz)(dppe)]n(BF4)n·2nH2O·nMeOH (2), [Ag2(tptz)2(dppp)2](BF4)2(3) and [Ag2(tptz)2(dppb)](BF4)2(4) were obtained from the reactions of AgBF4 and diphosphine Ph2P(CH2) nPPh2 (Lpp, n=1–4) in the presence of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) in MeOH–DMF. Single crystal analyses showed that the closed metallocyclic unit [Ag2(Lpp)2]2+ with double Lpp bridges was obtained in (1) and (3) with an odd number of n, while an open metallochain (Ag2Lpp)2+ with a single bridge formed in (2) and (4) with n being even. Coordination modes for the diphosphines are directly related to the rigid tptz ligand with a large π-system.

Synthesis and Antimicrobial Activity of New Schiff Bases Having the –SiOR Group ( R = CH 3 or CH 2 CH 3 ), and their Transition Metal Complexes

Abstract: Two new Schiff base ligands containing −SiOCH3 or −SiOCH2CH3 groups, 4-{[(3-trimethoxysilanepropyl)imino]methyl}benzene-1,3-diol (1) Hmsb and 4-{[(3-triethoxysilanepropyl)imino]methyl}benzene-1,3-diol (5) Hesb, have been synthesized by the reaction of 2,4-dihydroxybenzaldehyde with 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. Six new transition metal [CuII, NiII and CoII complexes of these Schiff Base ligands were prepared. The complexes are formed by coordination of N, O atoms of the ligands. Their structures were confirmed by elemental analyses, 1H nmr, i.r. and u.v.–vis. spectral data. The analytical data shows that the metal-to-ligand ratio in the Schiff Base complexes contains silane in 1:2. In addition, the antimicrobial activity of (1) Hmsb and (5) Hesb Schiff ligands, and their [M(msb)2] and [M(esb)2] type coordination compounds, were investigated

Five-coordinate cobalt(II), nickel(II) and zinc(II) complexes derived from 2-pyridine-2-yl-3-(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one. The crystal structure of the cobalt(II) complex

Abstract: The synthesis of cobalt(II), nickel(II) and zinc(II) complexes of 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)1,2-dihydroquinazolin-4(3H)-one is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.-vis.,i.r., 1D n.m.r., 2D hetcor and mass) and thermal studies. The cobalt(II) complex crystallizes as pink crystals in the monoclinic crystal system, space group P21/n with a = 10.066(6) Angstrom over circle, b= 15.929(9) Angstrom over circle, c = 12.624(7) Angstrom over circle, \alpha =90.00(9)degrees, \beta = 110.850 (8)degrees, \gamma = 90.00, V = 1891.5(18) Angstrom over circle (3) and Z = 4. The geometry around the cobalt atomis distorted trigonal bipyramidal with T = 0.83 [structuralparameter, T = (\beta - \alpha)/60; where \alpha and \beta are the two basal angles in a five coordinate complex].

Electrochemical characterization of phthalocyanine derivatives carrying a bulky triester unit on each benzo group

Abstract: The focus of the present work is to gain more insight into the electrochemical behavior of newly synthesized Co II , Zn II , Cu II , and Pd II phthalocyanines with tetra-tricarbethoxyethyl substituents at the peripheral position. A more exhaustive electrochemical study of the complexes was done to determine the desired wisdom for the usage of the complexes as a functional material. A comparative study of the voltammetric measurements of these complexes showed that while Zn II , Cu II , and Pd II phthalocyanines exhibited up to four common phthalocyanine ring reductions, Co II phthalocyanine gave a metal-centered oxidation, a reduction and a ligand-centered reduction process. By contrast observation of the splitting of the second reduction process of Pd II phthalocyanine suggests aggregation of the complex. Diffusion coefficients of all complexes were determined by both the cyclic voltammetry and the potential step chronocoulometry techniques. Diffusion coefficients of the reduced and oxidized forms of the redox couples of the complexes were also calculated by the potential step chronocoulometry technique. Diffusion coefficients of the reduced forms of the electrode products of the complexes were found to be slightly higher than that of the oxidized forms.

Template syntheses involving the carbon acid nitroethane. Synthesis and characterization of copper(II) complexes of a 16-membered tetraaza macrocycle

Abstract: New square-planar Cu(II) complexes of 3,11-dimethyl-3,11-dinitro-1,5,9,13-tetraazacyclohexadecane and 1,11-diamino-6-methyl-6-nitro-4,8-diazaundecane cations have been prepared from the one-pot template condensation of [Cu(pn)2]2+ (pn=1,3-diaminopropane) in MeOH with CH2O and EtNO2 in the presence of a noncoordinating base. Reduction of the nitro group in the (3,11-dimethyl-3,11-dinitro-1,5,9,13-tetraazacyclohexadecane)copper(II) cation, may be achieved by Zn/acid reduction. The Cu(II) complex of the reduced form of the ligand, namely (3,11-diammonio-3,11-dimethyl-1,5,9,13-tetraazacyclohexadecane)copper(II), has also characterized. With the macrocyclic ligand, rac and meso isomers have been identified, the meso form being the major product. Elemental analyses, i.r. and u.v.–vis. spectroscopy, f.a.b. mass spectra conductometric, magnetic measurements and cyclic voltammetry have been used to characterize the complexes.

Synthesis and Characterization of Transition Metal Methanesulfonates and their Catalytic Behavior in Biginelli Reactions

Abstract: A series of transition metal methanesulfonates were prepared and characterized by FTIR and TG. Characteristic peaks for the methyl and sulfonyl groups were observed in the i.r. spectra. The number of crystal waters and the process of dehydration and decomposition were determined by TG. The catalytic behavior of transition metal methanesulfonates in Biginelli one-pot cyclocondensation of aldehydes, 1,3-dicarbonyl compounds and urea in absolute EtOH under refluxing temperatures was investigated. The products, 3,4-dihydropyrimidinones, were characterized by elemental analysis, 1H n.m.r. and FTIR. The experimental results showed transition metal methanesulfonates were efficient for the Biginelli reaction.

Bis(2,2′-bipyridine)cobalt(III) complexes containing asymmetric ligands: Synthesis, DNA-binding and photocleavage studies

Abstract: Three new CoIII complexes: [Co(bpy)2(pdtb)]3+ (1), [Co(bpy)2(pdta)]3+ (2) and [Co(bpy)2(pdtp)]3+ (3) have been synthesized and characterized. The DNA binding behavior of the CoIII complexes has been investigated by spectroscopic methods and viscosity measurements. The results indicate that the size and shape of the intercalated ligand have a marked effect on the binding affinity of complexes involving CT-DNA. Complexes (2) and (3) have been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation. Photocleavage mechanisms are proposed.

The Mercury(II) Catalyzed Ligand Exchange Between Hexacyanoferrate(II) and Pyrazine in Aqueous Medium

Abstract: The kinetic and mechanistic studies of HgII catalyzed exchange of coordinated cyanide in hexacyanoferrate(II) by pyrazine (Pz) were monitored by following the appearance of the yellow complex [Fe(CN)5Pz]3− at 440 nm corresponding to metal ligand charge transfer (MLCT) transitions at temp=25.0±0.1 °C, pH=2.5±0.02 and ionic strength, I=0.1 m (KNO3). The effect of pH, ionic strength and the concentrations of [Fe(CN)6]4− and Pz on the rate of reaction were also studied and explained. To investigate the dependency of catalytic activity of HgII, the initial rates were determined at several concentrations of HgII, keeping the concentration of other reactants constant. The kinetic observations suggest that the substitution follows an interchange dissociative (I d ) mechanism and proceeds via formation of a solvent-bound intermediate. The repetitive spectral scan is also provided as evidence for the exchange of cyanide ions by pyrazine in [Fe(CN)6]4−. Activation parameters have also been evaluated and provided support for the proposed mechanistic scheme.

Biomimetic oxovanadium(IV) and (V) complexes with a tridentate (N,N,O)-donor hydrazonic ligand. Two X-ray crystal structure modifications of (2-acetylpyridine-benzoylhydrazonato)dioxovanadium(V)

Abstract: Two oxovanadium(IV) and (V) complexes with 2-acetylpyridine-benzoylhydrazone have been prepared and characterized. The analytical methods used included elemental analysis, i.r., FAB+ m.s., 51V-n.m.r. and e.p.r. X-ray diffractometry from single crystals as well as from microcrystalline material were also performed. Molecular modeling was used to calculate the complex structures in a vacuum and their vibrational frequencies. Octahedral coordination is suggested for the complex acetylacetonato(2-acetylpyridine-benzoylhydrazonato)-oxovanadium(IV) (1), for which good agreement was verified between calculated and observed i.r. data. Two crystal structure modifications of (2-acetylpyridine-benzoylhydrazonato)dioxovanadium(V) (2) have been determined by X-ray diffraction methods. In both crystalline modifications the molecular structure of the complex shows a distorted trigonal bipyramidal VN2O3 coordination. The molecular structure, found experimentally for (2), was compared with the theoretically calculated one. The results validate the theoretical method.

Synthesis, Crystal Structure and NLO Properties of a Novel Ruthenium(II) Complex with Unusual Coordination Mode

Abstract: A new Schiff base 4-[N-hydroxyethyl-N-(methyl)amino]benzaldehyde S-methyl dithiocarbazate (HL, where H is a dissociable proton) and the ruthenium complex [Ru(bpy)2L]PF6 (bpy = 2,2′-bipyridine) have been synthesized. The structural determinations of the ligand and its ruthenium complex, by X-ray crystallography, show that the ligand is coordinated as a monoanionic bidentate N, S-donor, forming a four-member chelate ring with a bite angle of 65.91°. The complex shows intense MLCT transitions in the visible region. Fluorescent and electrochemical properties have been also studied. The complex in DMF solution exhibited a strong two-photon absorption (t.p.a.) at 532 nm nanosecond laser pulses. The t.p.a. coefficient β, t.p.a. cross-section σ and the third-order optical nonlinearity χ(3) of the complex and the ligand have been determined by the Z-scan technique.

In vitro inhibitory effect of polyoxometalates on human tumor cells

Abstract: H7[NiV13O38] was synthesized from K7[NiV13O38] using an ion exchange method. Then Pr2H[NiV13O38] was obtained by double decomposition of H7[NiV13O38] with Pr2(CO3)3. The actual amount of praseodymium measured by elemental analysis coincides with the designed amount of praseodymium in Pr2H[NiV13O38]. The i.r. spectra suggested that the [NiV13O38]7− anion did not collapse after the ion exchange and double decomposition. The 51V n.m.r. spectrum of Pr2H[NiV13O38] showed four peaks and their ratio of the relative intensity was 4:4:4:1. This result agrees with the chemical environment of V atoms in the [NiV13O38]7− anion. In vitro antitumor activities of polyoxometalates on several human tumor cells have been investigated using the MTT method. Pr2H[NiV13O38] is the most effective polyoxometalate tested in this study for inhibiting KB cell. Pr2H[NiV13O38] also showed remarkable inhibitory effect on some other tumor cells: HCT, Bel, B16, BCAP and ESCL cells. These results indicate that Pr2H[NiV13O38] is a potent broad spectrum antitumor agent. The structure type of polyoxometalates greatly influences their antitumor activity: the order of structure type for inhibiting KB cell is: [NiV13O38]7− > [Mo␣7O24]6− > Anderson structure ≫ Keggin structure ≫ Dawson structure. Moreover, the nature of the polyatom in the polyoxometalates also greatly influences their antitumor activity: the polyatom order for inhibiting KB cell is: V > Mo ≫ W. On the other hand, the nature of the counter cation and the heteroatom in the polyoxometalates exerted a relatively small influence on the inhibitory effect against the KB cell, although the praseodymium salt of [NiV13O38]7− showed a higher antitumor activity than its potassium salt.

Synthesis, characterization and ascorbic acid oxidase mimetic catalytic activity of copper(II) picolyl hydrazone complexes

Abstract: Four new picolyl hydrazones were prepared via Schiff-base condensation of picolonic acid hydrazide with α-formyl-(L1), α-acetyl-(L2), α-benzoyl-(L3) pyridine and α-formyl-(L4) thiophene. Copper(II) complexes of these hydrazones and a series of copper(II) complexes containing (L2) and various anions (Cl, Br, NO3, SCN, SO4, ClO4, AcO, PF6 and BF4) have been synthesized. Elemental, thermal analysis, molar conductivity, magnetic moment measurements and spectral (i.r., electronic and e.s.r.) studies have been used to characterize the prepared compounds. The overall structure and reactivity of the reported copper(II) chelates critically depend on the ligand structure and the nature of counter anion incorporated in the complex molecule. Octahedral [complex (7)], square-pyramidal [complex (8)] and square-planar monomeric species [complexes (1–6), (9) and (10)] and a dimeric structure with oxygen bridge in square-planar geometry [complexes (11) and (12)] were suggested. The reported copper(II) complexes exhibit promising oxidase catalytic activity towards the aerobic oxidation of vitamin C. A linear correlation exists between the oxidase catalytic activity and the Lewis-acidity of the central copper(II) ion created by the donating properties of the parent ligand, as well the irregularity of the coordination environment. The probable mechanistic implications of the catalytic oxidation reactions are discussed.

Copper(II) complexes with 18-membered decaaza macrocycles: synthesis, characterization and catalytic activity

Abstract: New square-planar copper(II) complexes of 18-membered decaaza macrocyclic ligands: 5,6,14,15-tetramethyl-1,3,4,7,8,10,12,13,16,17-decaazacyclooctadecane (Me4[18]aneN10); 1,10-dimethyl-(Me2Me4[18]aneN10); 1,10-diethyl-(Et2Me4[18]aneN10); 1,10-dipropyl-(Pr2Me4[18]aneN10); 1,10-dibutyliso-(Bu2Me4[18]aneN10) and 1,10-dibenzyl-5,6,14,15-tetramethyl-1,3,4,7,8,10,12,13,16,17-decaazacylooctadecane [(Benzyl)2Me4[18]aneN10)] have been prepared by a one-pot template condensation of formaldehyde and 2,3-butanedihydrazone with alkyl and benzylamine in the presence of copper(II) ion. The complexes of the decaaza macrocycle have been characterized by elemental analyses, i.r., u.v.–vis., conductometric and magnetic measurements. The spectra of [Cu(R2Me4[18]ane N10)](ClO4)2shows that the four nitrogen (α-diimine) atoms are coordinated to the copper(II) ion. These complexes are found to be effective catalysts for the selective oxidation of tetrahydrofuran to yield the corresponding tetrahydrofuran-2-one and a small amount of tetrahydrofuran-2-ol and 4-hydroxybutyraldehyde, using diluted H2O2 as the oxidant.

Synthesis, characterization and antitumour activities of some synthetic curcuminoid analogues and their copper complexes

Abstract: The cytotoxic and antitumour activities of four curcuminoid analogues, namely 1,7-diphenyl-1,6-heptadiene-3,5-dione (HL1), 1,7-bis(4-methoxyphenyl)-1,6-heptadiene-3,5-dione (HL2), 1,7-bis(3,4-dimethoxyphenyl)-1,6-heptadiene-3,5-dione (HL3), 1,7-bis(3,4-dihydroxyphenyl)-1,6-heptadiene-3,5-dione (HL4) and their CuII complexes were investigated.The Cu complexes were found to be more active as antitumour agents compared to the free curcuminoids, in both in vitro studies and in increasing the life span of tumour bearing mice. The synthesis and characterization of the curcuminoid analogues and their CuII chelates employing u.v., i.r., 1 H-n.m.r., e.s.r. and mass spectral studies are also included in this report.

New Soluble Coordination Chain Polymers of Nickel(II) and Copper(II) ions and their Biological Activity

Abstract: A new tetraoxime ligand, (2E, 3E, 9E, 10E)-1, 4, 8, 11-tetraazacyclotetradecane-2, 3, 9, 10-tetrone tetraoxime has been prepared by the template condensation of 1,3-propanediamine and cyanogen-di-N-oxide, obtained by treating (E, E)-dichloroglyoxime in CH2Cl2 with Na2CO3 at −10 °C. The coordination chain polymers {[(pnngH2)2Ni]n (5) and [(pncgH2)2Cu]n(6)} of two transition metal ions, [Ni(II) and Cu(II)] with the vic-dioxime ligand have been prepared. The oxime ligand acts as a polydentate ligand bending through nitrogen atoms in the presence of a base, as do most of the vic-dioximes. In the complexes, the chloride ions coordinate to the nickel and copper ions. The structures of these novel vic-dioxime compounds are proposed on the basis of the elemental analyses, molar conductance data, i.r., and U.v.–visible are presented. Elemental analyses indicate a ligand metal ratio of 1:1 in the coordination polymers. Conductivity measurements have shown that mono- and polynuclear complexes are non-electrolytes. In addition, anti-microbial activities of the compounds have been investigated.

Complexes of iron(II), iron(III) and zinc(II) with condensation derivatives of 2-acetylpyridine and oxalic or malonic dihydrazide. Crystal structure of tris[(1-(2-pyridyl)ethylidene)hydrazine]iron(II) perchlorate

Abstract: Complexes of zinc and iron with N′, N′2-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (H2L1) and N′ ,N′2-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide (H2L2) were prepared. ZnII complexes with both ligands have an octahedral geometry. In the complex of ZnII with H2L1, the ligand is coordinated as a tridentate species in the monoanionic form, building two five-membered rings around ZnII. Three remaining coordination sites are occupied by water molecules, and in the outer sphere there is a ClO 4− ion. In the other ZnII complex, the H2L2 ligand is coordinated in the enol form as a tetradenate species, forming a five-memebered, a six-membered and a seven-membered ring, the remaining coordination sites being occupied by water molecules, while in the outer sphere there are two ClO 4− ions. The FeIII complex with H2L2 is a high-spin octahedral complex. The ligand is coordinated in the enol form, in a tetradentate fashion via pyridine and hydrazone nitrogens. The remaining two coordination sites in the complex are occupied by water molecules and a Cl− ion, and in the outer sphere there are two Cl− anions. The octahedral FeIII complex obtained from the reaction of FeCl3·6H2O and H2L1 in absolute ethanol has the formula [Fe(HL1)Cl2(H2O)]·1.5H2O. However, during coordination of the H2L1 ligand to FeIII in water, oxidative degradation of the side chain (–CO–CO–) and reduction of FeIII to FeII occurs, affording octahedral tris(1-(2-pyridyl)ethylidenehydrazine] ironII perchlorate, as confirmed by X-ray structure analysis.

Copper(II), nickel(II), cobalt(II) and zinc(II) complexes of 2-[2-(6-methylbenzothiazolyl)azo]-5-dimethylaminobenzoic acid: synthesis, spectral, thermal and molecular modelling studies

Abstract: Complexes of copper(II), nickel(II), cobalt(II), and zinc(II) with 2-[2-(6-methylbenzothiazolyl)azo]-5-dimethylaminobenzoic acid have been prepared and characterized by elemental analysis, vibrational spectra, magnetic susceptibility measurements, conductance measurements and e.p.r. spectra. Stability constants have been evaluated potentiometrically. Electronic spectra, magnetic susceptibility measurements and molecular modeling studies support a distorted square planar geometry around the metal ions. Vibrational spectra indicate the coordination of the azo group, nitrogen of benzothiazole, the carboxylate anion and the acetate ion on complexation with the metal ion. All complexes are found to be monomers. The stability of the complexes follow the order: copper(II) > nickel(II) > cobalt(II) > zinc(II).

Synthesis and antibacterial activity of cefoxitin metal complexes

Abstract: Cefoxitin (Hcefoxi) interacts with transition metal ions to give [M(cefoxi)Cl] complexes [M=Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)] which were characterized by physicochemical and spectroscopic methods. A tetrahedral geometry is suggested for their structure, where the cefoxitin behaves as a monoanionic tridentate ligand. The complexes have been screened for antibacterial activity against several bacteria, and the results show that they are less active than the parent cefoxitin.

Palladium salicylaldimine complexes containing boronate esters

Abstract: Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na2PdCl4 afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes. Condensation of salicylaldehyde (2-HOC6H4C(O)H) with H2NC6H4Bpin (pin=1,2-O2C2Me4) afforded the boron-containing Schiff bases, 2-HOC6H4C(H)=NC6H4Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na2PdCl4 afforded complexes of the type PdL2 (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.

Synthesis and structural characterization of a fully conjugated macrocyclic tetraaza(14)-membered Schiff base and its bivalent metal complexes

Abstract: A novel 14-membered macrocyclic Schiff base derived from 3-cinnamalideneacetoacetanilide and o-phenylenediamine acts as a tetradentate and strongly conjugated ligand to form a cationic solid complex with CuCl2/NiCl2/CoCl2/ZnCl2. The ligand and the complexes were characterized by the usual spectral and analytical techniques. The main i.r. band of the macrocyclic Schiff base was compared to that of its metal complexes. The C=N bands are shifted to the lower wave number. The cyclic voltammogram of the copper complex shows that the macrocyclic ligand is able to stabilize the copper(III) oxidation state. The e.s.r. spectra of the copper complex in DMSO solution at room temperature and liquid N2 temperature were recorded and their salient features thoroughly discussed. The antimicrobial screening tests were also recorded and gave good results in the presence of metal ions in the ligand system.

Biophysical and biochemical investigation on the binding of a manganese–cyanonitrosyl complex with DNA

Abstract: The interaction of a cyanonitrosyl–manganate complex with DNA has been studied by uv–vis spectroscopy, circular dichroism, fluorescence and gel electrophoresis techniques As the DNA 260 nm band remained insensitive to interaction, the interaction ratio was determined by monitoring the CN−→ Mn LMCT band observed at 222 nm, and the interaction ratio was found to be in the complex (D): DNA (P)=1:030 from the spectrophotometric titration The above-mentioned physical measurements indicate that the binding mode is not intercalative and the cyanonitrosyl system is a groove binder

Mononuclear manganese(II) and manganese(III) complexes of N 2 O donors involving amine and phenolate ligands: absorption spectra, electrochemistry and crystal structure of [Mn(L 3 ) 2 ](ClO 4 )

Abstract: A number of mononuclear manganese(II) and manganese(III) complexes have been synthesized from tridentate N2O aminophenol ligands (HL1–HL5) formed by reduction of corresponding Schiff bases with NaBH4. Three types of tridentate N2O aminophenols have been prepared by reducing with NaBH4which are (a) Schiff bases obtained by bromo salicylaldehyde reaction with N,N-dimethyl/N,N-diethyl ethylene diamine (HL1, HL2), (b) Schiff bases obtained by condensing salicylaldehyde/bromo salicylaldehyde and picolyl amine (HL3, HL4), (c) pyridine-2-aldehyde and 2-aminophenol (HL5). All the manganese complexes have been prepared by direct addition of manganese perchlorate to the corresponding ligands and were characterized by the combination of i.r., u.v.–vis spectroscopy, magnetic moments and electrochemical studies. The u.v.–vis spectra of all of the manganese(III) complexes show two weak d–d transitions in the 630–520 nm region, which support a distorted octahedral geometry. The electron transfer properties of all of the manganese(III) complexes (1–4 and 6) exhibit mostly similar characteristics consisting two redox couples corresponding to the Mn III → Mn II reductions and Mn III → Mn IV oxidations. The electronic effect on the potential has also been studied by changing different substituents in the ligands. In all cases, an electron-donating group stabilizes the higher oxidation state and electron withdrawing group prefers the lower oxidation state. The cyclic voltammogram of [Mn II (L5)2] shows an irreversible oxidation Mn II → Mn III at −0.88 V, followed by another quasi-reversible oxidation Mn III → Mn IV at +0.48 V. The manganese(III) complex (3) [Mn(L3)2]ClO4has been characterized by X-ray crystallography.

Synthesis, Characterization and Anti-oxidative Activity of Cobalt(II), Nickel(II) and Iron(II) Schiff Base Complexes

Abstract: Six complexes, M(HL)2 · nH2O (M=Co, Ni and Fe; n=4) with two ligands, 2-carboxy-benzaldehydebenzoylhydrazone (H2L1) and 2-carboxybenzaldehyde-(4′-methoxy)benzoylhydrazone (H2L2), have been synthesized and characterized on the basis of elemental analyses, molar conductivities, i.r. spectra and thermal analyses. In addition, the suppression ratio for O 2 - (a) and the suppression ratio for OH· (b) were determined with a 72 spectrophotometer. The 50% inhibition [IC50 (a) and IC50 (b)] of the complexes were studied. This study demonstrated that the complexes have activity in the suppression of O 2 - (a) and OH· (b). In general, the antioxidative activities increased as the concentration of these complexes increased up to a selected extent. The complexes exhibit more effective antioxidants than the ligands and the series of the ligand (H2L2) are better than the series of the ligand (H2L1) do.