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Schiff Base Ligands (schiff + base_ligand)

Distribution by Scientific Domains
Chemistry96%

Kinds of Schiff Base Ligands

  • tridentate schiff base ligand
    		•

    Selected Abstracts

    Application of a Carbon Paste Electrode Modified with a Schiff Base Ligand to Mercury Speciation in Water

    ELECTROANALYSIS, Issue 11 2005
    Montserrat Colilla
    Abstract A carbon paste electrode, modified with benzylbisthiosemicarbazone is used for mercury speciation in water samples. Mercury ion is selectively accumulated on the electrode surface at open circuit and its analysis was performed by cyclic voltammetry or square-wave voltammetry (SWV). A detection limit of 8,,g L,1 (3,) was found for 15,min of accumulation using SWV as measurement technique. The effect of several metallic ions and organic substances on voltammetric signal is examined. For speciation purposes, a ligand competition methodology between ligands in solution and electrode is used. Model mercury complexes are characterized as a function of their dissociation kinetics. The method was applied to mercury speciation in water samples from the Jarama River in Madrid. [source]

    Synthesis, Structure and Magnetic Properties of a Tetranuclear Copper(II) Complex on the Basis of a 2-Substituted Glucopyranoside Schiff Base Ligand,

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2006
    Anja Burkhardt
    Abstract Condensation of a derivatized 2-aminoglucose fragment with salicylaldehyde affords the new sugar-based Schiff base ligand benzyl 4,6- O -benzylidene-2-deoxy-2-salicylideneamino-,- D -glucopyranoside (H2L). The reaction of the dibasic ligand H2L with [Cu(CH3COO)2]·H2O leads to the formation of the tetranuclear copper(II) complex [{Cu(L)}4] (3) by a self-assembly process. The X-ray structural analysis of complex 3 which crystallizes together with two molecules of chloroform and one molecule of ethanol in the space group P212121 revealed for all copper atoms a NO3 coordination environment with a square-planar geometry. The tetranuclear molecule 3 consists of four chiral building blocks {Cu(L)} with the rare 2,3-coordination of the trans -configured donor atoms of the sugar backbone. The observed coordination mode of the building blocks exemplifies how chitosan-derived polysaccharide ligands can act as a chiral support for transition-metal complexes. The C-3 alcoholate oxygen atoms of the carbohydrate unit is bridging adjacent {Cu(L)} moieties resulting in an eight-membered Cu4O4 ring with a boat-like conformation. Temperature-dependent magnetic measurements of 3 indicate moderate antiferromagnetic interactions between the four copper(II) ions with a coupling constant of J = ,130 cm,1.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Enantioselective Silylcyanation of Aldehydes and Ketones by a Titanium Catalyst Prepared from a Partially Hydrolyzed Titanium Alkoxide and a Schiff Base Ligand

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009
    Kazuhiko Yoshinaga
    Abstract In the presence of small amount (0.2,1.0 mol%) of a titanium complex catalyst prepared from a partially hydrolyzed titanium alkoxide and an optically active tridentate Schiff base ligand, the enantioselective silylcyanation of aldehydes and ketones proceeded in a short reaction time at room temperature to afford the corresponding optically active cyanohydrin derivatives in excellent chemical yield with high enantiomeric excess (86,97% ee). The results indicate that partially hydrolyzed titanium alkoxides are a promising titanium source for the preparation of efficient catalysts for asymmetric synthesis. [source]

    Synthesis, Crystal Structure, and Catalytic Properties of Novel Dioxidomolybdenum(VI) Complexes with Tridentate Schiff Base Ligands in the Biomimetic and Highly Selective Oxygenation of Alkenes and Sulfides

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2010
    Abdolreza Rezaeifard
    Abstract Four novel dioxidomolybdenum(VI) complexes [MoO2(Lx)(CH3OH)] have been synthesized, using 2[(E)-(2-hydroxy-2-phenylethylimino)methyl]phenol derivatives as tridentate ONO donor Schiff base ligands (H2Lx) and MoO2(acac)2. A monoclinic space group was determined by X-ray crystallography from single-crystal data of a sample of these new complexes. The epoxidation of alkenes by using tert -butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were efficiently enhanced with excellent selectivity under the catalytic influence these new MoVI complexes. The high efficiency and relative stability of the catalysts have been observed by turnover numbers and UV/Vis investigations. The electron-poor and bulky ligands promoted the effectiveness of the catalysts. [source]

    Guest-Inclusion Behavior of Double-Strand 1D Coordination Polymers Based on N,N, -Type Schiff Base Ligands

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2008
    Qing Wang
    Abstract Four double-strand one-dimensional (1D) coordinationpolymers, namely, {[Ni(N3Py)2(NO3)2]·(C6H6)x·C2H5OH}n (1), [Cd(ImBNN)2(CH3C6H4SO3)2]n (2), {[Co(N3OPy)2(H2O)2](ClO4)2·C6H6·H2O}n (3), and {[Co(N3OPy)2(H2O)2](ClO4)2·(C8H10)x}n (4) were obtained from the assembly of three N,N, -type Schiff base ligands, 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (N3Py), 2,5-bis(4,-(imidazol-1-yl)benzyl)-3,4-diaza-2,4-hexadiene (ImBNN), and bis[4-(3-pyridylmethylenemino)phenoxy]methane (N3OPy), with transition-metal ions. All complexes were characterized by single-crystal X-ray diffraction, X-ray powder diffraction, and FTIR measurements. The guest-inclusion behavior of these complexes were investigated by thermogravimetric and X-ray powder diffraction analyses. The structural relationship between the ligands and the cavity sizes and packing fashions have been discussed to elucidate the distinctive guest-inclusion behavior of these complexes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Syntheses, Structures and Magnetic Properties of Trinuclear CuIIMIICuII (M = Cu, Ni, Co and Fe) and Tetranuclear [2×1+1×2] CuIIMnII,2CuII Complexes Derived from a Compartmental Ligand: The Schiff Base 3-Methoxysalicylaldehyde Diamine Can also Stabilize a Cocrystal

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2010
    Arpita Biswas
    Abstract The present investigation describes syntheses, characterization and studies of the mononuclear compound [CuIIL,(H2O)] (1), the triangular, trinuclear monophenoxido-bridged compounds [{CuIIL}2MII(H2O)2](ClO4)2·nH2O [2 (M = Cu, n = 0), 3 (M = Ni, n = 3), 4 (M = Co, n = 0), 5 (M = Fe, n = 0)] and the tetrametallic self-assembled complex [{CuIILMnII(H2O)3}{CuIIL}2](ClO4)2·H2O (6) derived from compartmental Schiff base ligand, H2L, which is the [2+1] condensation product of 3-methoxysalicylaldehyde and trans -1,2-diaminocyclohexane. Single-crystal X-ray structures of 2, 5 and 6 were determined. Two pairs of terminal···central metal ions in the trinuclear cores in 2 and 5 are monophenoxido-bridged. Interestingly, the CuO6 and FeO6 environments have tetragonally compressed octahedral geometries. On the other hand, the structure of 6 reveals that it is a [2×1+1×2] cocrystal of one diphenoxido-bridged dinuclear [CuIILMnII(H2O)3]2+ dication and two mononuclear [CuIIL] moieties. Cocrystallization in 6 takes place as a result of water encapsulation. The variable-temperature (2,300 K) magnetic susceptibilities of compounds 2,6 have been measured. The exchange integrals obtained are: the CuII3 compound 2, J = ,78.9 cm,1; the CuIINiIICuII compound 3, J = ,22.8 cm,1; the CuIICoIICuII compound 4, J = ,7.8 cm,1; the CuIIFeIICuII compound 5, J = ,3.0 cm,1; the CuII3MnII compound 6, J = ,15.1 cm,1. The monophenoxido-bridging core in 3 and 4 has been proposed after comparison of the structures and magnetic properties of these two compounds with those of 2, 5 and related other compounds. This paper presents rare examples of monophenoxido-bridged CuIIMIICuII (M = Cu, Ni, Co and Fe) compounds, provides an understanding of the structures from magnetic exchange integrals, and, most importantly, reports on the first example of a cocrystal derived from a 3-methoxysalicylaldehyde diamine compartmental ligand. [source]

    Enantioselective Silylcyanation of Aldehydes and Ketones by a Titanium Catalyst Prepared from a Partially Hydrolyzed Titanium Alkoxide and a Schiff Base Ligand

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009
    Kazuhiko Yoshinaga
    Abstract In the presence of small amount (0.2,1.0 mol%) of a titanium complex catalyst prepared from a partially hydrolyzed titanium alkoxide and an optically active tridentate Schiff base ligand, the enantioselective silylcyanation of aldehydes and ketones proceeded in a short reaction time at room temperature to afford the corresponding optically active cyanohydrin derivatives in excellent chemical yield with high enantiomeric excess (86,97% ee). The results indicate that partially hydrolyzed titanium alkoxides are a promising titanium source for the preparation of efficient catalysts for asymmetric synthesis. [source]

    A family of thioxanthato ruthenium and osmium aryls

    ISRAEL JOURNAL OF CHEMISTRY, Issue 3 2001
    Swarup Chattopadhyay
    The title complexes of type M(RL2)(PPh3)2(CO)(S2CSEt) (2a: M = Ru; 2b: M = Os) have been synthesized in excellent yields by reacting M(RL1)(PPh3)2(CO)X (1a: M = Ru, × = Cl; 1b: M = Os, × = Br) with potassium ethyl thioxanthate and have been characterized with the help of spectral and electrochemical data. The RL2 ligand in 2 is the imine-phenol tautomer of N-C6H4R(p)-4-methylsalicylaldimine (R = Me, MeO, Cl) coordinated at the carbanionic-C2 atom only while RL1 in 1 is the iminium-phenolato tautomer chelated via carbanionic-C2 and phenolato-O atoms. The synthetic reaction is thus attended with tautomerization of the Schiff base ligand. It is also associated with a rotation of the ligand by ,180° around the M,C bond in order to exclude steric repulsion. These features have been revealed by structure determination of 2a (R = Me). The metallated aldimine ring is found to be highly noncoplanar (dihedral angle ,40°) with the thioxanthate chelate ring due to steric repulsion originating from the relatively large size of the sulfur atom. This phenomenon, which is absent in both the precursor 1 (R = Me) and in the carboxylate analogue Ru(MeL2)(PPh3)2(CO)(O2CMe), 7, has distinctive effects on bond parameters of 2a (R = Me). Thus the two Ru,P bonds in 2a (R = Me) differ in length by as much as 0.06 Å. The thioxanthate 2 is thermodynamically more stable than the precursor 1 as well as the carboxylate 7. Accordingly, both of these are irreversibly transformed to 2a (R = Me) upon treatment with thioxanthate. [source]

    Interactions between dimers of {1,1,-[o -phenylenebis(nitrilomethylidyne)]di-2-naphtholato-,4O,N,N,,O,}nickel(II)

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009
    Anita Blagus
    In the title compound, [Ni(C28H18N2O2)], the NiII centre has a square-planar coordination geometry in which the Schiff base ligand acts as a cis - O,N,N,,O,-tetradentate ligand. The crystal structure is built up of centrosymmetric dimer units stacked into chains along the [010] direction. Adjacent chains associate via C,H...O hydrogen bonding only, leading to a two-dimensional sheet-like structure consisting of layers parallel to (10). The cofacial dimeric complex contains an Ni...Ni contact of 3.291,(4),Å. [source]

    The chiral helical structure of a copper(II) complex with a tridentate Schiff base ligand

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009
    Wen-Juan Shi
    In the title salt, catena -poly[[[aquacopper(II)]-,-3-(2-pyridylmethyleneamino)propanoato-,4N,N,,O:O,] perchlorate], {[Cu(C9H9N2O2)(H2O)]ClO4}n, the monomeric unit contains a square-based pyramidal CuII centre. The four basal positions are occupied by a tridentate anionic Schiff base ligand which furnishes an NNO-donor set, with the fourth basal position being occupied by an O-donor atom from the carboxylate group of an adjacent Schiff base ligand. The coordination sphere is completed by a water molecule at the apical position. Interestingly, each carboxylate group in the ligand forms a syn,anti -configured bridge between two CuII centres, leading to left-handed chiral helicity. The framework also exhibits O,H...O hydrogen bonds involving the water molecules and an O atom of the perchlorate anion. [source]

    {4,10-Bis[2-(2-oxidobenzyl­idene­amino-,2N,O)benz­yl]-1,7-dioxa-4,10-diaza­cyclo­dodecane-,4O1,N4,O3,N10}ytterbium(III) perchlorate acetonitrile solvate

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2006
    Marina González-Lorenzo
    In the crystal structure of the title compound, [Yb(C36H38N4O4)]ClO4·CH3CN, the ytterbium ion is eight-coordinated and deeply buried in the cavity of the dianionic Schiff base ligand. The coordination polyhedron may be described as a distorted square anti­prism that shows a twist angle of 29.5,(1)° between the two square planes. The receptor adopts a syn arrangement, with both pendent arms on the same side of the crown group, and there are two helicities (one associated with this layout of the pendent arms and the other with the conformation of the crown ring), which give rise to enantiomeric pairs of diastereoisomers, viz. ,(,,,,) and ,(,,,,). [source]

    Syntheses, characterization and biological studies of zinc(II), copper(II) and cobalt(II) complexes with Schiff base ligand derived from 2-hydroxy-1-naphthaldehyde and selenomethionine

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 10 2010
    Xueguang Ran
    Abstract Novel zinc(II), copper(II), and cobalt(II) complexes of the Schiff base derived from 2-hydroxy-1-naphthaldehyde and D, L -selenomethionine were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and powder XRD. The analytical data showed the composition of the metal complex to be ML(H2O), where L is the Schiff base ligand and M = Co(II), Cu(II) and Zn(II). IR results confirmed the tridentate binding of the Schiff base ligand involving azomethine nitrogen, naphthol oxygen and carboxylato oxygen atoms. 1H NMR spectral data of lithium salt of the Schiff base ligand [Li(HL)] and ZnL(H2O) agreed with the proposed structures. The conductivity values of complexes between 12.50 and 15.45 S cm2 mol,1 in DMF suggested the presence of non-electrolyte species. The powder XRD studies indicated that Co(II) complex is amorphous, whereas Cu(II) and Zn(II) complexes are crystalline. The results of antibacterial and antifungal screening studies indicated that Li(HL) and its metal complexes are active, but CuL(H2O) is most active among them. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Biocidal and catalytic efficiency of ruthenium(III) complexes with tridentate Schiff base ligands

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2010
    S. Arunachalam
    Abstract The reaction of the Schiff bases (obtained by condensing isatin with o -aminophenol/o -aminothiophenol/o -aminobenzoic acid) with [RuX3(EPh3)3] (where X = Cl/Br; E = P/As) in benzene afforded new, air-stable Ru(III) complexes of the general formula [Ru(L)X(EPh3)2] (L = dianion of tridentate Schiff bases). In all these reactions, the Schiff base ligand replaces one triphenylphosphine/triphenylarsine and two chlorides/bromides from the ruthenium precursors. The complexes were characterized by elemental analyses, spectral (FT,IR, UV,vis, 1H and 13C NMR for the ligands, and EPR) and electrochemical studies. All the metal complexes exhibit characteristic LMCT absorption bands in the visible region. The catalytic reactivity proved these complexes to be efficient catalysts in the oxidation of alcohols and CC coupling. All the complexes were screened for their biocidal efficiency against bacteria such as Staphylococcus epidermidis and Escherichia coli and fungi such as Botrytis cinerea and Aspergillus niger at 0.25, 0.50 and 1% concentrations. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Homo- and heteropolynuclear copper(II) complexes containing a new diimine,dioxime ligand and 1,10-phenanthroline: synthesis, characterization, solvent-extraction studies, catalase-like functions and DNA cleavage abilities

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2009
    Bülent Dede
    Abstract A series of homo-, heterodinuclear and homotrinuclear copper(II) complexes containing a new Schiff base ligand and 1,10-phenanthroline were synthesized. Based on results of elemental analyses, FTIR, 1H- and 13C-NMR spectra, conductivity measurements and magnetic susceptibility measurements, the complexes had general compositions {[Cu(L)(H2O)M(phen)2](ClO4)2 [M = Cu(II), Mn(II), Co(II)]} and {[Cu3(L)2(H2O)2](ClO4)2}. The metal:L:phen ratio is 2:1:2 for the dinuclear copper(II) complexes and the metal:L ratio was 3:2 for the trinuclear copper(II) complex. The liquid,liquid extraction of various transition metal cations [Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II), Hg(II)] from the aqueous phase to the organic phase was carried out using the diimine,dioxime ligand. It was concluded that the ligand can effectively be used in solvent extraction of copper(II) from the aqueous phase to the organic phase. Furthermore, catalytic activitiy of the complexes for the disproportionation of hydrogen peroxide was also investigated in the presence of imidazole. Dinuclear copper(II),manganese(II) complex has some similarity to manganese catalase in structure and activity. The interaction between these complexes and DNA has also been investigated by agarose gel electrophoresis; we found that the homo- and heterodinuclear copper complexes can cleave supercoiled pBR322 DNA to nicked and linear forms in the presence of H2O2. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    UV/Vis to NIR Photoconduction in Cyclopalladated Complexes

    CHEMISTRY - AN ASIAN JOURNAL, Issue 7 2009
    Nicolas Godbert
    Abstract Funky discotics: Photoconductivity is measured in newly synthesized cyclopalladated metallomesogens exhibiting hexagonal columnar mesophases at room temperature. The tuning of the HOMO/LUMO energy levels by modification of the chain/core linkage (ester 1 vs ether 2) makes compound 2 photoconductive across the whole UV/Vis/NIR range. The incorporation of a rigid core, formed by a cyclopalladated azobenzene fragment bonded to an ancillary Schiff base ligand, into molecules with 12 or 11 peripheral alkyl chains has been successfully achieved. These new complexes, 1 and 2, respectively, are columnar liquid crystals between room temperature and about 50,°C. Both cyclometallated and ancillary ligands have been polyalkylated through either aryl ester (electron-withdrawing group) or aryl ether (electron-releasing group) linkages, in order to tune the HOMO/LUMO energy levels. The photoconductive properties of 1 and 2 have been studied as a function of their absorption properties before and after annealing, from the UV/Vis to NIR region. Compared with the reference compounds, tris-alkynyl benzene discotics, these new materials gave similar performances (,/I,8×10,13,S,cm,W,1 with E=10,V,,m,1 at ,=370,nm). Moreover, complex 2 shows a normalized photoconductivity ,/I=8.5×10,13,S,cm,W,1 at ,=760,nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors. [source]

    Synthesis, Crystal Structure, and Catalytic Properties of Novel Dioxidomolybdenum(VI) Complexes with Tridentate Schiff Base Ligands in the Biomimetic and Highly Selective Oxygenation of Alkenes and Sulfides

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2010
    Abdolreza Rezaeifard
    Abstract Four novel dioxidomolybdenum(VI) complexes [MoO2(Lx)(CH3OH)] have been synthesized, using 2[(E)-(2-hydroxy-2-phenylethylimino)methyl]phenol derivatives as tridentate ONO donor Schiff base ligands (H2Lx) and MoO2(acac)2. A monoclinic space group was determined by X-ray crystallography from single-crystal data of a sample of these new complexes. The epoxidation of alkenes by using tert -butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were efficiently enhanced with excellent selectivity under the catalytic influence these new MoVI complexes. The high efficiency and relative stability of the catalysts have been observed by turnover numbers and UV/Vis investigations. The electron-poor and bulky ligands promoted the effectiveness of the catalysts. [source]

    Aluminium Complexes of a Phenoxyimine Ligand with a Pendant Imidazolium Moiety: Synthesis, Characterisation and Evidence for Hydrogen Bonding in Solution

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2008
    Stefano Milione
    Abstract Novel alkylaluminium complexes (phim)AlMe2 (1) and(phimid)AlR2+Br, [R = Me (2), R = iBu (3)] bearing the Schiff base ligands 3,5- tBu2 -2-(OH)C6H2CH=NiPr (phim -H) and3,5- tBu2 -2-(OH)C6H2CH=NCH2CH2[CH(NCHCHNiPr)]Br(phimid -H·Br) have been prepared and fully characterised. Complexes 1,3 each have a tetrahedral structure, with the aluminium atom surrounded by the oxygen and nitrogen atoms of the chelating ligand and two alkyl groups. The structures of phimid -H·Br and of complex 1 have been determined by X-ray diffraction studies. Investigation of the solution structures of 1,3 by 1H NMR spectroscopy revealed that the coordinated phimid ligand is involved in hydrogen bonding with bromide anion. Treatment of 1 with B(C6F5)3 led smoothly to (phim)Al(C6F5)Me (4) by transfer of a C6F5 group from MeB(C6F5)3, to the initially formed coordinatively unsaturated cationic intermediate. In contrast, treatment of 2 with one equiv. of B(C6F5)3 afforded the cationic monomethyl species (phimid)AlMeBr+,MeB(C6F5)3, (5), stabilised by the coordination of the bromide anion acting as a Lewis base.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Pseudo-Octahedral Schiff Base Nickel(II) Complexes: Does Single Oxidation Always Lead to the Nickel(III) Valence Tautomer?

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2008
    Olaf Rotthaus
    Abstract With the aim of establishing correlations between the ligand structure and the oxidation site in nickel complexes from Schiff base ligands, five ligands and their nickel complexes have been synthesized. The prototypical asymmetric Schiff base ligand HL1 contains both phenol and pyridine pendant arms with a pivotal imine nitrogen atom. Ligands HL2,5 differ from HL1 by either their phenolate para substituent, the hybridization of the pivotal nitrogen atom, and/or the N-donor properties of the pyridine moiety. The five complexes [Ni(L1,5)2] are obtained by treating the corresponding ligands with 0.5 equiv. of Ni(OAc)2·4H2O in the presence of NEt3. X-ray crystal-structure diffraction studies as well as DFT calculations reveal that [Ni(L1,5)2] involves a high-spin nickel(II) ion within a pseudo-octahedral geometry. The two ligands are arranged in a meridional fashion when the pivotal nitrogen atom is an imine {as in [Ni(L1,2)2] and [Ni(L4,5)2]}, while the fac isomer is preferred in [Ni(L3)2] (amino pivotal nitrogen atom). [Ni(L1)2] is characterized by an oxidation potential at ,0.17 V vs. Fc+/Fc. The one-electron-oxidized species [Ni(L1)2]+ exhibits an EPR signal at g = 2.21 attributed to a phenoxyl radical that is antiferromagnetically coupled to a high-spin NiII ion. [Ni(L2)2] differs from [Ni(L1)2] by the phenolate para substituent (a tert -butyl instead of the methoxyl group) and exhibits an oxidation potential that is ca. 0.16 V higher. Compared to [Ni(L1)2]+ the cation [Ni(L2)2]+ exhibits a SOMO that is more localized on the metal atom. The EPR and electrochemical signatures of [Ni(L3)2]+ are similar to those of [Ni(L1)2]+, thus showing that an imino to amino substitution compensates for a methoxy to tert -butyl one. Replacement of the pyridine by a quinoline group in [Ni(L4,5)2] makes the complexes slightly harder to oxidize. The EPR signatures of the cations [Ni(L4,5)2]+ are roughly similar to those of the pyridine analogs [Ni(L1,2)2]+. The oxidation site is thus not significantly affected by changes in the N-donor properties of the terminal imino nitrogen atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Checking the Route to Cluster Helicates

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2008
    Manuel R. Bermejo
    Abstract The aim of the work described here was to test the general applicability of our recently reported route to cluster helicates and to carry out a systematic study to relate the structural and coordinative properties of the organic strands with the microarchitectures of the resulting cluster helicates. Nine new ZnII, CuI and AgI complexes were prepared from three Schiff base ligands [H2La: bis(4-methyl-3-thiosemicarbazone)-2,6-diacetylpyridine; H2Lb: bis(4-methyl-3-thiosemicarbazone)-2,6-diacetylbenzene; H2Lc: bis(4-ethyl-3-thiosemicarbazone)-2,6-diacetylbenzene]. The experimental data confirm that AgI and CuI tetranuclear cluster helicates were obtained with a [M4(Lx)2] stoichiometry, and this finding demonstrates the general applicability of the synthetic route. The cluster helicates presented in this work were characterized for the first time in solution by NMR spectroscopy. In addition, six of the nine complexes were characterized by X-ray diffraction studies, and three of them were found to be tetranuclear cluster helicates. A detailed study of these three crystal structures leads us to state that the changes introduced in the organic strands do not prevent the assembly of the tetranuclear cluster dihelicates, but they do affect the microarchitectures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Guest-Inclusion Behavior of Double-Strand 1D Coordination Polymers Based on N,N, -Type Schiff Base Ligands

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2008
    Qing Wang
    Abstract Four double-strand one-dimensional (1D) coordinationpolymers, namely, {[Ni(N3Py)2(NO3)2]·(C6H6)x·C2H5OH}n (1), [Cd(ImBNN)2(CH3C6H4SO3)2]n (2), {[Co(N3OPy)2(H2O)2](ClO4)2·C6H6·H2O}n (3), and {[Co(N3OPy)2(H2O)2](ClO4)2·(C8H10)x}n (4) were obtained from the assembly of three N,N, -type Schiff base ligands, 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (N3Py), 2,5-bis(4,-(imidazol-1-yl)benzyl)-3,4-diaza-2,4-hexadiene (ImBNN), and bis[4-(3-pyridylmethylenemino)phenoxy]methane (N3OPy), with transition-metal ions. All complexes were characterized by single-crystal X-ray diffraction, X-ray powder diffraction, and FTIR measurements. The guest-inclusion behavior of these complexes were investigated by thermogravimetric and X-ray powder diffraction analyses. The structural relationship between the ligands and the cavity sizes and packing fashions have been discussed to elucidate the distinctive guest-inclusion behavior of these complexes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Nickel and zinc complexes with a monodentate heterocycle and tridentate Schiff base ligands: self-assembly to one- and two-dimensional supramolecular networks via hydrogen bonding

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009
    Xiao-Hua Chen
    In the complex (morpholine)[2-hydroxy- N,-(5-nitro-2-oxidobenzylidene)benzohydrazidato]nickel(II), [Ni(C14H9N3O5)(C4H9NO)], (I), the NiII center is in a square-planar N2O2 coordination geometry. The complex bis[,-2-hydroxy- N,-(2-oxidobenzylidene)benzohydrazidato]bis[(morpholine)zinc(II)], [Zn2(C14H10N2O3)2(C4H9NO)2], (II), consists of a neutral centrosymmetric dimer with a coplanar Zn2(,2 -O)2 core. The two ZnII centers are bridged by phenolate O atoms. Each ZnII center exhibits a distorted square-pyramidal stereochemistry, in which the four in-plane donors come from the O,N,O,-tridentate 2-hydroxy- N,-(2-oxidobenzylidene)benzohydrazidate(2,) ligand and a symmetry-related phenolate O atom, and the axial position is coordinated to the N atom from the morpholine molecule. There are intramolecular phenol,hydrazide O,H...N hydrogen bonds present in both (I) and (II). In (I), square-planar nickel complexes are linked by intermolecular morpholine,morpholine N,H...O hydrogen bonds, leading to a one-dimensional chain, while in (II) an infinite two-dimensional network is formed via intermolecular hydrogen bonds between the coordinated morpholine NH groups and the uncoordinated phenolate O atoms. [source]

    Biocidal and catalytic efficiency of ruthenium(III) complexes with tridentate Schiff base ligands

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2010
    S. Arunachalam
    Abstract The reaction of the Schiff bases (obtained by condensing isatin with o -aminophenol/o -aminothiophenol/o -aminobenzoic acid) with [RuX3(EPh3)3] (where X = Cl/Br; E = P/As) in benzene afforded new, air-stable Ru(III) complexes of the general formula [Ru(L)X(EPh3)2] (L = dianion of tridentate Schiff bases). In all these reactions, the Schiff base ligand replaces one triphenylphosphine/triphenylarsine and two chlorides/bromides from the ruthenium precursors. The complexes were characterized by elemental analyses, spectral (FT,IR, UV,vis, 1H and 13C NMR for the ligands, and EPR) and electrochemical studies. All the metal complexes exhibit characteristic LMCT absorption bands in the visible region. The catalytic reactivity proved these complexes to be efficient catalysts in the oxidation of alcohols and CC coupling. All the complexes were screened for their biocidal efficiency against bacteria such as Staphylococcus epidermidis and Escherichia coli and fungi such as Botrytis cinerea and Aspergillus niger at 0.25, 0.50 and 1% concentrations. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Ruthenium(II) complexes incorporating tridentate Schiff base ligands: synthesis, spectroscopic, redox, catalytic and biological properties

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2010
    N. Sathya
    Abstract A series of new diamagnetic ruthenium(II) complexes of the type [RuCl(CO)(B)(L)] (where B = PPh3, AsPh3 or Py; L = monobasic tridentate Schiff base ligands derived from o -aminophenol or o -aminothiophenol with ethylacetoacetate or ethylbenzoylacetate) have been synthesized and these complexes were characterized by physico-chemical and spectroscopic methods. Cyclic voltammograms of all the complexes show quasi-reversible oxidation in the range 0.24,1.05 V and the quasi-reversible reduction in the range , 0.14 to , 0.51 V. The observed redox potentials show little variation with respect to the replacement of triphenyl phosphine/arsine by pyridine. The complexes were tested as catalysts in the oxidation of primary and secondary alcohols using molecular oxygen at room temperature and also in CC coupling reactions. Further, the antibacterial properties of the free ligands and their metal complexes were evaluated against certain bacteria such as Escherichia coli and Staphylococcus aureus. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Synthesis, characterization, electrochemical, catalytic and antimicrobial activity studies of hydrazone Schiff base ruthenium(II) complexes

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2010
    N. Thilagavathi
    Abstract Four tridentate O, N, O donor Schiff base ligands were prepared by the reaction of substituted benzhydrazide and appropriate salicylaldehyde. The complexes of these ligands were synthesized by refluxing the ligands with ruthenium(II) starting complexes of the formula [RuHCl(CO)(EPh3)2B] in benzene, where E = P or As; B = PPh3 or AsPh3 or pyridine. The newly synthesized complexes were characterized by elemental, spectral (FT-IR, UV and NMR) and electrochemical data. On the basis of the above studies, an octahedral structure has been proposed for all the complexes. The catalytic efficiency of the complexes in aryl,aryl couplings and oxidation of alcohols was examined and their inhibition activity against the growth of the micro-organisms was also examined. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Synthesis of 4-substituted styrene compounds via palladium catalyzed Suzuki,Miyaura reaction using bidentate Schiff base ligands

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2009
    Yan Liu
    Abstract Air-stable symmetric Schiff base have been synthesized and proved to be efficient ligands for Suzuki,Miyaura reaction between aryl bromides and arylboronic acids using PdCl2(CH3CN)2 as palladium source under aerobic conditions. The coupling reaction proceeded smoothly using N,N -bis(anthracen-9-ylmethylene)benzene-1,2-diamine (L7) as ligand to provide 4-substituted styrene compounds in good yields. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Metal-based antitumor, cytotoxic and antimicrobial activity: pharmacological evaluation of Knoevenagel condensate ,-diketone Schiff base thiosemicarbazone Cu(II) and Zn(II) complexes

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 7 2009
    N. Raman
    Abstract Knoevenagel condensate Schiff base ligands [L = 3-cinnamalideneacetylacetone-thiosemicarbazone (CAT)/3-cinnama- lideneacetylacetoneethylthiosemicarbazone (CAET)/3-cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)] and their copper/zinc complexes were synthesized. They were characterized by analytical and spectral techniques. From these data it was found that the ligands adopt square-planar geometry on metalation with Cu2+ and Zn2+. To evaluate the antitumor and cytotoxic activity of the synthesized complexes in mice and human cancer cell lines, the antitumor activity of the complexes was evaluated against an Ehrlich ascites carcinoma (EAC) tumor model. The activity was assessed using survival time and short-term in vitro cytotoxic activity. Oral administration of complexes (100 mg/kg) increased the survival time. The cytotoxic activity of complexes was evaluated using human breast cancer (MDA-MB-231), colon cancer (HCT-116) and nonsmall lung cancer (NCI-H-23) cell lines. Both the complexes possessed significant antitumor and cytotoxic activity on EAC and human cancer cell lines. The in vitro antimicrobial screening effect of the investigated compounds was also tested against the various organisms by well diffusion method. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Behavioural dynamics in the biological control of pests: role of silicon complexes

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2008
    Savita Belwal
    Abstract The complexes of silicon (IV) with Schiff base ligands (L1H and L2H of isatin derivatives) having a sulfur and oxygen donor system were prepared by the reactions in methanol environment. These were isolated and characterized by elemental analysis, molecular weight determinations and conductance measurements. On the basis of electronic, infrared, 1H, 13C and 29Si NMR spectral studies, trigonal bipyramidal geometry was suggested for the resulting complexes. These data support preferential binding of sulfur and oxygen atom to the silicon atom. The disease resistance activities of the ligands and their corresponding complexes were examined successfully in in vitro and in vivo experiments, against pathogenic fungi and bacteria. Results were quite encouraging and these were compared with the standard pesticides Bavistin and Streptomycin. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Synthesis, spectroscopy, thermal and biological aspect of novel six-coordinated dimeric iron(III) mixed-ligand complexes

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2008
    M. N. Patel
    Abstract The mixed-ligand complexes of iron(III) with 1-cyclopropyl-6-fluoro-4-oxo-7-piperazin-1-yl-1,4-dihydroquinoline-3-carboxylic acid and various neutral bidentate Schiff base ligands were prepared. The structure of mixed-ligand complexes was investigated using spectral, physicochemical and elemental analyses. Biocidal activity was determined using agar plate technique against Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Salmonella typhi, Escherichia coli and Serratia marcescens. The result showed a significant increase in a biocidal activity compared with parent ligands, metal salts and standard drugs (ofloxacin, levofloxacin). DNA binding and cleavage studies were carried out using absorption titration and gel electrophoresis techniques, respectively. The binding constant of Fe(III) complexes was obtained in the range 2.5,4.0 × 104M,1. The DNA binding and cleavage efficacy were raised in mixed-ligand complexes as compared with parental ligands and metal salts. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Intramolecular phenylborane complexes with monobasic bidentate Schiff bases

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2007
    Shweta Gaur
    Abstract A series of intramolecular complexes with Schiff base ligands having N,S and N,O donor systems were synthesized in an open vessel under microwave irradiation (MWI) using a domestic microwave oven. The reaction time has been brought down from hours to seconds with improved yield as compared with the conventional heating. The complexes have been characterized on the basis of elemental analysis, conductance measurements and spectroscopic analysis. Based on the IR, 1H NMR, 11B NMR and 13C NMR spectroscopic studies, a tetrahedral geometry has been proposed for the resulting complexes. The compounds have been screened in vitro against bacteria and fungi to test their antimicrobial property and in vivo in male albino rats to test their antifertility property. The testicular sperm density, motility and density of cauda epididymal spermatozoa along with biochemical parameters of reproductive organs have been examined and discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Single-crystal EPR studies of a perchlorate-bridged dimeric copper(II) complex with 2-[(4-methyl-pyridin-2-ylimino)-methyl]-phenol

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007
    R. Srinivasan
    Abstract A new dimeric perchlorate-bridged copper(II) complex with the Schiff's base ligand 2-[(4-methyl-pyridin-2-ylimino)-methyl]-phenol has been synthesized. The complex has been characterized using elemental analysis, ultraviolet,visible and infrared spectroscopy, conductivity, magnetic studies and EPR techniques. Single-crystal EPR studies indicate that zero-field splitting (D) is relatively small, and that the half-field transition is not observed due to its low intensity. An interesting observation in the frozen solution is that the low-field side of the zero-field splitting line splits into seven lines, due to interaction between the two copper ions. The magnetic susceptibility data indicate a weak ferromagnetic property and that the complex is a 1:2 electrolyte. Another set of EPR resonances corresponding to higher D and g values, compared to the system reported, are noticed, whose origin is not yet known. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]