Showing papers in "Transition Metal Chemistry in 1999"

Antimicrobial activity studies of the binuclear metal complexes derived from tridentate Schiff base ligands

Abstract: Three novel tridentate Schiff base ligands derived from␣the 3-hydroxysalicylaldehyde (H2L1), 4-hydroxysalicylaldehyde (H2L2) and 5-bromosalicylaldehyde (H2L3) with a new amine N-(pyridyl)-2-hydroxy-3-methoxy-5-aminobenzylamine (2) have been prepared. The ligands and their metal complexes have been characterized by elemental analyses, conductivity and magnetic susceptibility measurements, i.r., electronic absorption and 1H and 13C n.m.r. spectroscopy. All complexes are binuclear and, in some, the H2O molecules are coordinated to the metal ion. Antimicrobial activities of the ligands and their complexes have been tested against to the Bacillus subtilis IMG 22 (bacteria), Micrococcus luteus LA 2971 (bacteria) Saccharamyces cerevisiae WET 136 (yeast), and Candida albicans CCM 314 (yeast). Thermal properties of all complexes have been studied by t.g. and d.t.a techniques.

Antimicrobial activity studies of mononuclear and binuclear mixed-ligand copper(II) complexes derived from Schiff base ligands and 1,10-phenanthroline

Abstract: Mixed-ligand complexes of copper(II) with 1,10-phenanthroline and various Schiff bases have been prepared and characterized by elemental analysis, electronic and i.r. spectra, magnetic moment and molar conductance data. The Schiff base behave as bidentate ligands, and the mixed-ligand copper(II) complexes of the ligands HL1′′, HL2′′ and HL4′′ are binuclear. The conductivity data for all the complexes are consistent with those expected for an electrolyte. Antimicrobial activities of some of the ligands and complexes have been tested against Bacillus megaterium and Candida tropicalis. 1H and 13C n.m.r. spectra have been recorded in order to solve the solution structure of the ligands. Thermal properties of all complexes have been studied by the d.t.a. and t.g.a. techniques.

Transition metal complexes of bidentate Schiff base ligands

Abstract: New Schiff base ligands derived from vanillin (HL1), 4-dimethylaminobenzaldehyde (HL2) and 3,5-di-t-butyl-4-hydroxybenzaldehyde (HL3) with N-(pyridyl)-3-methoxy-4-hydroxy-5-aminobenzylamine (2) and their copper(II), cobalt(II), nickel(II), oxovanadium(IV) and zinc(II) transition metal complexes have been synthesized and characterized by elemental analyses, electronic and i.r. spectra, molar conductance data and by 1H and 13C n.m.r. spectra. The results indicate that the ligands coordinate through azomethine nitrogen and phenolic oxygen to the metal ions. In like manner, it was found that the pyridine and amine nitrogen atoms are not coordinated to the metal ions. The 1H and 13C n.m.r. spectral data confirmed the suggested structure for the Schiff base ligands, and the mass spectra results confirmed the proposed structure of the ligands. The antimicrobial activity properties of the ligands and their metal complexes have been studied.

Cobalt(ii) complexes with 2-aminoacetophenone n(4)-substituted thiosemicarbazones

Abstract: Cobalt(II) complexes with 2-aminoacetophenone thiosemicarbazone and three N(4)-substituted thiosemicarbazones have been prepared in EtOH solution and characterized by physical and spectral methods. I.r. and electronic spectra of the thiosemicarbazones and their complexes, along with physical properties of the complexes, have been obtained. The 2-aminoacetophenone thiosemicarbazones coordinate both as neutral and anionic ligands via the thiosemicarbazone moiety's imine nitrogen and thione/thiolato sulfur [on loss of the N(2) hydrogen].

Synthesis, characterization and antibacterial properties of Schiff bases and Schiff base metal complexes derived from 2,3-diamino- pyridine

Abstract: New copper(II), zinc(II) and nickel(II) Schiff base complexes derived from 2,3-diaminopyridine (DAPY) and selected aldehydes, namely salicylaldehyde (SalH), 4-hydroxybenzaldehyde (4-OHBenz) and 4-nitrobenzaldehyde (4-NO2Benz), and one mixed Schiff base, DAPY-{4-OHBenz}{SalH} were prepared and characterized by a combination of elemental analyses, i.r. and n.m.r. spectra, and magnetic susceptibility measurements. The Schiff bases and some of the metal complexes display antibacterial properties.

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

Abstract: 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.

Macrocyclic complexes of transition metals with divalent polyaza units

Abstract: A new series of 14–16-membered hexaazamacrocyclic complexes [ML1X2] and [ML2X2] (M = CoII, NiII, CuII and ZnII; X = Cl or NO3) have been synthesized by template condensation of phenylenediamine, primary diamines and formaldehyde solution 35% in MeOH and have been characterized by i.r., 1H-n.m.r., e.p.r., and u.v. spectroscopy as well as by magnetic susceptibility and conductivity measurements. An octahedral geometry has been suggested for all the complexes.

One-dimensional chain copper complexes cu(dien)(btrz)(clo4)2 and cu(en)2(btrz)(clo4)2 based on the bridging ligand 1,2-bis(1,2,4-triazole-1-yl)ethane (btrz)

Abstract: The reaction of diethylenetriamine (dien) and 1,2-bis(1,2,4-triazole-1-yl)ethane (btrz) with Cu(ClO4) · 6H2O forms [Cu(dien)(btrz)(ClO4)2] (1), and the reaction of [Cu(en)2(ClO4)2] (en = ethylenediamine) with btrz forms [Cu(en)2(btrz)(ClO4)2] (2). Complexes (1) and (2) were characterized by elemental analysis, i.r., electronic spectroscopy, e.s.r. and magnetic susceptibility. Their crystal structure was determined by X-ray diffraction. In complex (1), Cu is coordinated by a dien and two btrz, forming a distorted CuN5 square pyramid with one btrz bound at the apical position. In complex (2), Cu is coordinated by two en and two nitrogen atoms of btrz forming an elongated octahedron. Both complexes have a one-dimensional chain structure in which btrz ligands bridge between pairs of Cu atom.

Manganese(II) and palladium(II) complexes containing a new macrocyclic Schiff base ligand: antibacterial properties

Abstract: Complexes of tetradentate macrocyclic Schiff base ligand, L, with MnII and PdII ions have been synthesized by the template condensation of 1,10-phenanthroline-2, 9-dicarboxaldehyde, 2,3-diamino-1,4-naphthoquinone and 1,2-dibromoethane in EtOH. The complexes were characterized by physicochemical and spectroscopic methods and an octahedral geometry is suggested for their structure. They have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of penicillin.

The existence of ferrous ferricyanide

Abstract: Evidence in the literature on the synthesis of ferrous ferricyanide is critically discussed Pyrolysis and pressure effects on Prussian Blue lead to ferrous ferrocyanide together with decomposition by-products, and not to ferrous ferricyanide The latter compound could be a precursor in the formation of Turnbull's Blue or an excited state of Prussian Blue, but it is not a stable chemical species

Iron(ii) and nickel(ii) mixed-ligand complexes containing 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline

Abstract: Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mossbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.

Electro-optical properties of the first rhenium-hydrazone complex, fac-Re(CO)3(dpknph)*Cl

Abstract: Reaction between Re(CO)5Cl and dpknph in PhMe under reflux gave fac-Re(CO)3(dpknph)Cl in good yield. Both dpknph and fac-Re(CO)3(dpknph)Cl exhibit rich electro-optical properties that are sensitive to their surroundings and point to the potential use of these compounds in nonlinear optics and molecular sensing. Spectroscopic and electrochemical measurements on solutions of dpknph and fac-Re(CO)3(dpknph)Cl show that the metal complex undergoes faster electron/charge-transfer than the free ligand. Solvent variations show that the rate increases in the following order: DMSO>DMF>MeCN.

Synthesis, thermal and spectral studies of oxoperoxo and dioxo complexes of vanadium(V), molybdenum(VI) and tungsten(VI) with 2-(α-hydroxyalkyl/aryl)benzimidazole

Abstract: Reaction of 2-(α-hydroxymethyl)benzimidazole or 2-(α-hydroxyethyl)benzimidazole (LH) with the peroxovanadium(V) species, generated in situ by stirring V2O5, KOH and 30% aqueous H2O2, gives the corresponding complexes of formula K[VO(O2)L2]. Similar peroxo species of molybdenum and tungsten generated by stirring MoO3 or WO3·H2O with an excess of 30% aqueous H2O2 readily react with 2-(α-hydroxyethyl) benzimidazole in aqueous EtOH to give the peroxo complexes [MO(O2)L2] (M=Mo or W). The dioxo complexes of general formula [MO2L2] have also been isolated by the reaction of [MoO2(acac)2] or [WO2- (acac)2] (acacH=acetylacetone) with the above ligands and with 2-(α-hydroxybenzyl)benzimidazole. The dioxo complexes are white, whereas peroxo complexes are light yellow to orange. The peroxo complexes generally decompose in two steps: (i) the decomposition of the peroxo group and (ii) the decomposition of the alkyl/aryl group followed by decomposition of the complete ligand. On the other hand, decomposition of the dioxo complexes follows only in a later step. All the peroxo complexes exhibit three i.r. active vibrational modes at ca. 860 cm−1, 760 cm−1 and 600cm−1, characteristic of the η2-coordinated peroxo group. The dioxo complexes are dominated by the presence of two sharp bands in the 900 cm−1 region due to νsym(O=M=O) and νasym(O=M=O) modes. The ν(C=N) (ring) and ν(OH) shifts have also been measured in order to locate the coordination sites of the ligands. A broad band at ca. 400 nm in the peroxovanadium(V) complexes, while the absorption at ca. 350 nm in the peroxomolybdenum(VI) and tungsten(VI) complexes is assigned to the peroxo-metal charge transfer band.

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

Abstract: 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].

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

Abstract: 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.

Synthesis, characterization and biocidal studies of ruthenium(II) carbonyl complexes containing tetradentate Schiff bases

Abstract: Stable ruthenium(II) complexes of Schiff bases have been prepared by reacting [RuHCl(CO)(PPh3)2(B)] (B = PPh3, pyridine or piperidine) with bis(o-vanillin)ethylenediimine (valen), bis(o-vanillin)propylene-diimine (valpn), bis(o-vanillin)tetramethylenediimine (valtn), bis(o-vanillin)o-phenylenediimine (valphn), bis(salicylaldehyde)tetramethylenediimine (saltn) and bis(salicylaldehyde)o-phenylenediimine (salphn). These complexes have been characterised by elemental analyses, i.r., electronic, 1H- and 31P{1H}-n.m.r. spectral studies. In all the above reactions, the Schiff bases replace two molecules of Ph3P, a hydride and a halide ion from the starting complexes, indicating that the Ru–N bonds present in the complexes containing heterocyclic nitrogen bases are stronger than the Ru–P bond to Ph3P. The new complexes of the general formula [Ru(CO)(B)(L)] (B = PPh3, py or pip; L = tetradentate Schiff bases) have been assigned an octahedral structure. Some of the Schiff bases and the new complexes have been tested against the pathogenic fungus Fusarium sp.

Electrochemical studies of copper(II) complexes derived from bulky Schiff bases. The crystal structure of bis[N-(1- adamantyl)-salicylaldiminato]copper(II)

Abstract: Three Schiff base ligands and their corresponding copper(II) complexes have been prepared and characterized. Elemental analyses, mass spectra, i.r., electronic spectra, μeff and the X- ray crystal structure for one of the complexes, as well as elemental analyses, mass spectra, i.r., electronic and 1H n.m.r. spectra of the ligands, have been obtained. The X-ray study shows that the geometry around the metal atom is intermediate between square planar and tetrahedral. Electrochemical studies on the complexes reveal a dependence of the CuII/CuI potentials on the extent of distortion of the planar structure observed in solid state.

Complexes of 2,5-dihydroxy-1,4-benzoquinone and chloranilic acid with second and third row transition elements

Abstract: The synthesis of new 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ) and chloranilic acid (H2CA) complexes cis-[Mo2O5L2]2− (L = DHBQ, CA), [W2O5(DHBQ)2]2−, [WO2(CA)2]2−, trans-[UO2(DHBQ)]·H2O, and trans-[UO2(CA)2]2− is described. Raman, i.r., 1H and 13C n.m.r spectra of the ligands and their complexes are reported and their structures discussed.

Platinum(II) complexes of 2-, 3-, and 4-formyl-pyridine thiosemicarbazone and 2-, 3- and 4-acetyl-pyridine thiosemicarbazone

Abstract: Seven platinum(II) complexes isolated from thiosemicarbazones derived from 2-, 3- and 4-formylpyridine and 2-, 3-, and 4-acetylpyridine have been characterised by microanalyses, molar conductivities and by their ir and 1H-nmr spectra

Soft template synthesis of (2,8-dithio-3,7-diaza-5-oxanonandithioamide-1,9) nickel(II) and (2,7-dithio-3,6-diazaoctadien-3,5-dithioamide-1,8)nickel(II) using a nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix

Abstract: Complexing processes leading under specific conditions to nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix systems in contact with aqueous-alkaline solutions (pH ∼ 12) containing dithiooxamide and formaldehyde or glyoxal, have been studied. It has been shown that template synthesis of macrocyclic co-ordination compounds, (2,8-dithio-3,7-diaza-5-oxanonandithioamide-1,9)nickel(II) and (2,7-dithio-3,6-diazaoctadien-3,5-dithioamide-1,8)nickel(II), occurs. Dithiooxamide, formaldehyde and glyoxal act as ligand synthons in this process.

Structure, solvatochromism, and solvation of trans-[Co-III(cyclam)(NCS)(2)](NCS) and the structure of [Co-II(Me(4)cyclam)(NCS)](2)[Co(NCS)(4)]MeOH

Abstract: The structures of trans-[CoIII(cyclam)(NCS)2](NCS) and of [CoII(Me4cyclam)(NCS)]2[Co(NCS)4]·MeOH have been established by X-ray diffraction methods. The solvatochromic behavior of the trans-[Co(cyclam)(NCS)2]+ cation in several binary aqueous solvent mixtures is reported. Transfer chemical potentials for this complex from H2O into MeOH-H2O mixtures have been established from solubility measurements on its thiocyanate salt. The solvatochromic behavior of this cation is discussed in the context of other solvatochromic inorganic complexes; its transfer chemical potentials are discussed in relation to those of other cobalt(III) complexes.

Tungstotellurates of the imidazolium and 4-methylimidazolium cations

Abstract: Tungstotellurates of the organic imidazolium and 4-methyl-imidazolium cations have been prepared and characterized by X-ray diffraction and i.r. spectroscopy. The [TeW6O24]6− anion is formed by close packing of oxygen atoms with Te and W atoms in distorted octahedral voids. In both compounds the organic cations are involved in hydrogen bonds, to the [TeW6O24]6− anion in [H2imz]6[TeW6O24] · 2(Himz) (1) and to Te(OH)6 units in [4-H2-methyl-imz]6[TeW6O24] · Te(OH)6 (2). Solution studies of (1) and (2) by 1H-, 183W- and 125Te-n.m.r. have been carried out. Thermogravimetric (t.g.) and calorimetric (d.s.c.) analyses were performed for both compounds.

Preparation of novel cobalt(III) complexes with dithiocarbimates derived from sulfonamides

Abstract: Reaction of potassium N-R-Sulfonyldithiocarbimates, K2(RSO2N=CS2) (R=Me, Ph, 4-MeC6H4, 2-MeC6H4, 4-ClC6H4, 4-BrC6H4), with CoCl2·6H2O, yielded the complex CoIII anions [Co(RSO2N=CS2)3]3-, which were isolated as their Bu4N+ salts. Elemental analyses, i.r. spectra and u.v.-vis. data were consistent with the formation of cobalt-sulfur diamagnetic octahedral (D3) complexes. The 1H and 13C n.m.r. spectra showed the expected signals for the Bu4N+ cation and the dithiocarbimate moieties. The 1H n.m.r. integrations were consistent with a 3:1 cation:anion ratio.

New macrocyclic complexes containing amide, imine and secondary amine functions

Abstract: 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.

Synthesis, properties and biological activity of organotin decatungstophosphates, Part 2

Abstract: Single isomers [(RSn)2PW10O38]5− [R = MeOCOCH2CH2, MeOCOCH(Me)CH2, NCCH2CH2] have been prepared and their structures have been determined by 183Wn.m.r. spectroscopy. The spectrum of [(MeOCOCH2 CH2Sn)2PW10O38]5− shows five equally intense peaks, which are ascribed to the C2 isomer formed by 1,4-substitution. The title complexes exhibit antitumor activity in vitro.

Preparation, spectral and structural characterization of (2-benzoylpyridine n(4)-methyl-n(4)-phenylthiosemicarbazonato) chloropalladium(ii)

Abstract: The synthesis, as well as spectral and structural characterization, of (2-benzoylpyridine-N(4)-methyl-N(4)-phenylthiosemicarbazonato)chloropalladium(II), [Pd(Bz4MePh)Cl], is described The unit cell contains two crystallographically independent molecules [Pd(1)(Bz4MePh)Cl], (1), and [Pd(2)(Bz4MePh)Cl], (2), stabilized by intra- and intermolecular hydrogen bonding The distance between the Pd(1) and Pd(2) centres is 35038(11) A The spectroscopic techniques used in this study are the following: uv-visible, ir and 1H nmr The protonation constants, determined spectrophotometrically, of the uncoordinated HBz4MePh are pKa1 = 1082 ± 003 and pKa2 = 409 ± 002

Complexation between vanadium(V) and citrate: spectroscopic and structural characterization of a dinuclear vanadium(V) complex

Abstract: Investigation of the aqueous coordination chemistry for citrate and vanadium(V) resulted in the isolation and characterization of a dinuclear vanadium(V) citrato complex (1) Na2K2[VO2(Hcit)]2 · 9H2O. Complex (1) is an intermediate between the fully deprotonated and diprotonated citrate vanadate. It may represent an early mobilized precursor in the biosynthesis of FeV-co, as well as a relevant model in the proton transport relay process between P-cluster pair to M-cluster pair. The complex has been characterized by elemental analyses and i.r. spectroscopy. Its i.r. spectra are consistent with a oxo-bridged dinuclear structure as revealed by a single crystal X-ray diffraction study.

The chemical behaviour of di(2-pyridyl)sulphide, dps. Crystal and molecular structure of μ-di(2-pyridyl)sulphidebis(trans-dichlorotriethylphosphine platinum(II)), [{Pt(PEt3)Cl2}2μ-dps] and its reactivity towards stannylated species

Abstract: The coordinating ability of the ligand di(2-pyridyl)sulphide, dps, was studied in several situations. Dps behaved as a bidentate chelating agent with SnX4 (X=Cl or Br) and also with Pd and Pt (PdCl2 and K2PtCl4), whereas with [Pt2(PR3)2Cl4], (R = Et or Ph), it formed bridging complexes: [{Pt(PR3)Cl2}2μ-dps]. The crystal and molecular structure of [{Pt(PEt3)Cl2}2μ-dps] was determined. This complex, as well as [M(dps)Cl2], (M = Pd or Pt), underwent reactions with SnCl2, which inserts into the M–Cl bonds producing heterobimetallic products, which are important in catalysis.

Nickel(II) complexes with dicyanamide and tetramines.

Abstract: Four new pseudohalide complexes of the type [NiL{N(CN)2}2] (L = N(CH2CH2NH2)3, TAA; triethylenetetramine, TTA) and [NiL{N(CN)2}]ClO4 have been prepared and characterized by spectroscopic and magnetic methods. The X-ray crystal structures of [Ni(TAA){N(CN)2}2] and [Ni(TTA){N(CN)2}2] have been determined, and analyses show that in both complexes the Ni ion posseses distorted octahedral geometry. The temperature dependence of the magnetic susceptibility of [Ni(TTA){N(CN)2}](ClO4) was measured, but no antiferromagnetic interaction was detected.

Magnetic properties of new copper(II) and [copper(II)]3-manganese(II) complexes of [14]N4 macrocyclic oxamides

Abstract: Four new complexes of [14]N4 macrocyclic oxamides, namely [CuL1], [CuL2], [(CuL1)3Mn](ClO4)3 and [(CuL2)3 Mn](ClO4)3 [L1 and L2 are the dianions of 2,3-dioxo-5,6: 3,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene (H2L1) and 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclo-tetradeca-7,11-diene (H2L2), respectively], have been prepared and characterized. The observed magnetic susceptibilities of the [(CuL1)3Mn] (ClO4)3 complex over the ca. 2–300 K range have been fitted to theoretical equations based on the Heisenberg spin Hamiltonian Ĥ=−2JŜMn(ŜCu1+ ŜCu2+ŜCu3) and molecular field approximation. The results indicated that both the intramolecular and intermolecular magnetic interactions are antiferromagnetic with JCuMn= −19.8cm−1 and zJ′=−1.41cm−1.