Imidazolate bridged Cu(II)-Cu(II) and Cu(II)-Zn(II) complexes of a terpyridinophane azamacrocycle: a solution and solid state study

The dinuclear Cu2+ and Zn2+ as well as the mixed Cu2+-Zn2+ complexes of a 5,5'-pentaazaterpyridinophane ligand (L) are able to incorporate imidazolate (Im-) as a bridging ligand. The crystal structure of [Cu(2)L(Im)(Br)(H2O)](CF(3)SO(3))(2).3H2O (1) shows one copper coordinated by the three pyridine nitrogens of the terpyridine unit, one nitrogen of the imidazolate bridge (Im-) and one bromide anion occupying the axial position of a distorted square pyramid. The second copper atom is coordinated by the remaining imidazolate nitrogen, the three secondary nitrogens at the centre of the polyamine bridge and one water molecule that occupies the axial position. Magnetic measurements have been performed in the 2.0-300.0 K temperature range. Experimental data could be satisfactorily reproduced by using an isotropic exchange model H = -JS(1)S(2) with J = -52.3 cm(-1) and g = 2.09. Potentiometric studies have provided details of the speciation and stability constants for the mixed Cu2+-L-HIm, Zn2+-L-HIm (HIm = imidazole) and Cu2+-Zn2+-L-HIm systems. The apparent stability constant obtained at pH = 9 for the addition of imidazole to the dinuclear Cu2+ complexes is one of the highest so far reported (log K = 7.5). UV-Vis spectroscopy and paramagnetic NMR data show that imidazole coordinates to the Cu2+ ions as a bridging imidazolate ligand from pH 5 to 10. Electrochemical reduction of the Cu2+-Zn2+-L complex occurs in two successive one-electron per copper ion quasi-reversible steps. The formal potential of the Cu2+-Zn2+-L/Cu+-Zn2+-L couple is close to that of SOD. The IC50 values measured at pH 7.8 by means of the nitro blue tetrazolium method show significant SOD activity for the dinuclear Cu2+ complexes (IC50 = 2.5 microM) and moderate activity for the Cu2+-Zn2+ mixed systems (IC50 = 30 microM).     

E.s.r., magnetic, optical and biological (SOD and antimicrobial) studies of imidazolate bridged Cu(II)-Zn(II) and Cu(II)-Ni(II) complexes with tris(2-amino ethyl)amine as capping ligand: a plausible model for superoxide dismutase

X-band e.s.r. and optical absorption spectra of the imidazolate bridged heterobimetallic complexes [(tren)Cu-E-Im-Zn-(tren)](ClO(4))(3) and [(tren)Cu-E-Im-Ni-(tren)](ClO(4))(3), where trentris(2-aminoethyl)amine, E-Im=2-ethylimidazolate ion and the related mononuclear complexes [Cu(tren)](ClO(4))(2) and [(tren)Cu-E-ImH)](ClO(4))(2) have been described. Biological activities (superoxide dismutase and antimicrobial) have also been measured and compared with reported complexes.     

Spectroscopic studies of bridged binuclear complexes of Co(II), Ni(II), Cu(II) and Zn(II)

Binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of general composition [M₂L^1-2(μ-Cl)Cl₂] · nH₂O with the Schiff-base ligands (where L¹H and L²H are the potential pentadentate ligands derived by condensing 2,6-diformyl-4-methylphenol with 4-amino-3-antipyrine and 2-hydroxy-3-hydrazinoquinoxiline, respectively) have been synthesized and characterized. Analytical and spectral studies support the above formulation. ¹H-NMR and IR spectra of the complexes suggest they have an endogenous phenoxide bridge, with chloride as the exogenous bridge atom. The electronic spectra of all the complexes are well characterized by broad d–d and a high intensity charge-transfer transitions. The complexes are chloro-bridged as evidenced by two intense far-IR bands centered around 270–280 cm⁻¹. Magnetic susceptibility measurements show that complexes are antiferromagnetic in nature. The compounds show significant growth inhibitory activity against fungi Aspergillus niger and Candida albicans and moderate activity against bacteria Bacillus cirroflagellosus and Pseudomonas auresenosa.     

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: electrochemical, magnetic and antimicrobial studies

Phenoxide bridged later first row transition metal(II) complexes have been prepared by the interaction of later 3d transition metal(II) chlorides with tetranucleating compartmental Schiff base ligand system derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-hydrazinobenzothiazole. Ligand and complexes were characterized by analytical, spectral (IR, UV-visible, ESR, FAB-mass and fluorescence), magnetic and thermal studies. All complexes are found to have octahedral geometry. The mutual influence of metal centres in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff base and its complexes have been screened for their antibacterial (against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa) and antifungal activities (against Aspergillus niger, and Candida albicans).     

Syntheses,structures, and properties of imidazolate-bridged Cu(II)-Cu(II) and Cu(II)-Zn(II) dinuclear complexes of a single macrocyclic ligand with two hydroxyethyl pendants

The imidazolate-bridged homodinuclear Cu(II)-Cu(II) complex, [(CuimCu)L]ClO(4).0.5H(2)O (1), and heterodinuclear Cu(II)-Zn(II) complex, [(CuimZnL(-)(2H))(CuimZnL(-)(H))](ClO(4))(3) (2), of a single macrocyclic ligand with two hydroxyethyl pendants, L (L = 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22,2,2,2(11,14)]triaconta-1,11,13,24,27,29-hexaene), have been synthesized as possible models for copper-zinc superoxide dismutase (Cu(2),Zn(2)-SOD). Their crystal structures analyzed by X-ray diffraction methods have shown that the structures of the two complexes are markedly different. Complex 1 crystallizes in the orthorhombic system, containing an imidazolate-bridged dicopper(II) [Cu-im-Cu](3+) core, in which the two copper(II) ions are pentacoordinated by virtue of an N4O environment with a Cu.Cu distance of 5.999(2) A, adopting the geometry of distorted trigonal bipyramid and tetragonal pyramid, respectively. Complex 2 crystallizes in the triclinic system, containing two similar Cu-im-Zn cores in the asymmetric unit, in which both the Cu(II) and Zn(II) ions are pentacoordinated in a distorted trigonal bipyramid geometry, with the Cu.Zn distance of 5.950(1)/5.939(1) A, respectively. Interestingly, the macrocyclic ligand with two arms possesses a chairlike (anti) conformation in complex 1, but a boatlike (syn) conformation in complex 2. Magnetic measurements and ESR spectroscopy of complex 1 have revealed the presence of an antiferromagnetic exchange interaction between the two Cu(II) ions. The ESR spectrum of the Cu(II)-Zn(II) heterodinuclear complex 2 displayed a typical signal for mononuclear trigonal bipyramidal Cu(II) complexes. From pH-dependent ESR and electronic spectroscopic studies, the imidazolate bridges in the two complexes have been found to be stable over broad pH ranges. The cyclic voltammograms of the two complexes have been investigated. Both of the two complexes can catalyze the dismutation of superoxide and show rather high activity.     

New oxamato-bridged trinuclear Cu(II)-Cu(II)-Cu(II) complexes with hydrogen-bond supramolecular structures: synthesis and magneto-structural studies

Three oxamato-bridged copper(II) complexes of formula [(Cu(H(2)O)(tmen)Cu(tmen))(mu-Cu(H(2)O)(Me(2)pba))](n)((PF(6))(2))(n).2nH(2)O (1), [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(ClO(4))(2).4H(2)O (2), and [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(PF(6))(2).4H(2)O (3), where Me(2)pba = 2,2-dimethyl-1,3-propylenebis(oxamato) and tmen = N,N,N',N'-tetramethylethylenediamine, have been synthesized and characterized. Their crystal structures were solved. Complex 1 crystallizes in the monoclinic system, space group P2(1), with a = 15.8364(3) A, b =8.4592(2) A, c = 15.952 A, beta = 101.9070(10) degrees, and Z = 2. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.69530(10) A, b = 18.2441(3) A, c = 31.6127(5) A, beta = 90.1230(10) degrees, and Z = 4. Complex 3 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.68970(10) A, b = 18.150 A, c = 32.1949(4) A, beta = 90.0820(10) degrees, and Z = 4. The three complexes have a central core in common: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine. The structure of complex 1 consists of trinuclear cationic entities connected by hydrogen bonds to produce a supramolecular one-dimensional array. The structure of complexes 2 and 3 consist of trinuclear cationic entities linked by pairs by hydrogen bonds between the water molecule of the central Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, forming a hexanuclear complex. The magnetic properties of the three complexes were studied by susceptibility vs temperature measurement. For complexes 1-3 the fit was made by the irreducible tensor operator (ITO). The values obtained were J(1) = -386.48 cm(-1) and J(2) = 1.94 cm(-1) for 1, J(1) = -125.77 cm(-1) and J(2) = 0.85 cm(-1) for 2, and J(1) = -135.50 cm(-1) and J(2) = 0.94 cm(-1) for 3. In complex 1, the coordination polyhedron of the terminal Cu(II) atoms can be considered as square pyramidal; the apical positions are filled by the oxygen atom from a water molecule in the former and a F atom of the hexafluorophosphate anion in the latter showing a quasi-planar [Cu(CuMe(2)pba)Cu] network. For complexes 2 and 3, the square pyramidal environment of the terminal Cu(II) ions was strongly modified. To our knowledge, this is the first time that the longest distance (apical) in complexes with oxamato derivatives and bidentate amines as blocking ligands has been reported in one of the oxamato arms. The great difference in J(1) values between 1 and the other two complexes is interpreted as an orbital reversal of the magnetic orbitals of the terminal Cu(II) ions in 2 and 3.     

Characterization studies of some bi- and tetradentate bifunctionalSchiff base complexes with Co(II), Ni(II), and Cu(II)

Co(II), Ni(II) and Cu(II) complexes of some bifunctional arylidene-o-phenylenediamineSchiff bases have been prepared. Formation, stoichiometry and stability of the complexes have been tested in solution using electronic spectral measurements. Characterization of the complexes has been accomplished primarily by elemental analysis, molar conductance as well as electronic and IR spectral measurements. It is concluded that theo,o-hydroxy derivative (L ₁) acts as a bivalent ONNO tetradentate ligand while the molecules of the other derivatives (L ₂-L ₅) are coordinated to the metal ions as bidentate NN ligands. The Cu(II)-L ₁ complex is suggested to possess a tetrahedral geometry whereas the other complexes are suggested to exhibit a distarted octahedral geometry. The different bands observed in the electronic spectra of the complexes inDMF solutions have been assigned to the -*,L M CT and d-d electronic transitions.

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Untersuchungen zur Charakterisierung einiger zwei- und vierzähniger bifunktionellerSchiffbasen-Komplexe mit Co(II), Ni(II) und Cu(II)

Zusammenfassung Es wurden die Co(II)-, Ni(II)- und Cu(II)-Komplexe einiger bifunktioneller Aryliden-o-phenylendiamin-Schiffbasen hergestellt. Unter Verwendung elektronenspektroskopischer Methoden wurde die Bildung, Stöchiometrie und Stabilität der Komplexe in Lösung untersucht. Die Charakterisierung erfolgte mittels Elementaranalysen, Leitfähigkeitsmessungen und Elektronen- bzw. IR-Spektroskopie. Es wird darauf geschlossen, daß daso,o-HydroxyderivatL ₁ als bivalenter vierzähniger ONNO Ligand wirkt, während die anderen Derivate (L ₂-L ₅) als zweizähnige NN Liganden an die Metallionen koordiniert sind. Für den Cu(II)-L ₁ Komplex wird eine tetraedrische Geometrie vorgeschlagen, währenddessen die anderen Komplexe eine verzerrte octaedrische Geometrie aufweisen. Die in den Elektronenspektren der Komplexe inDMF-Lösung auftretenden Banden werden den -*,L M CT und d-d Elektronenübergängen zugeordnet.

     

Thermogravimetric studies on some Cu(II) amine complexes

Thermogravimetric analysis of solid state bis-Cu(II) amine complexes CuL₂X₂, whereX=Cl^– or NO ₃ ^– andL=ethylenediamine (en), tetramethylethylenediamine (tmn),o-phenylenediamine (opd) and 2,2 bipyridyl (bpy), has been carried out and the kinetic parameters have been determined by fitting the observed mass losses corresponding to various steps using the Coats and Redfern equation. These studies show that the activation energies of these complexes decrease on changing the ligand in the order: bpy > opd > en > tmn. This trend can be attributed to the rigidity of the N-C-C-N skeleton in the bpy and opd ligands and steric crowding at the nitrogens in the tmn ligand. The majority of the decomposition steps were found to be composite in nature and frequently involved fractional groups expelled from the complexes. From the observation ofE _a> H, the thermal decomposition process of these complexes appears to be governed by the nucleation and growth mechanism.

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Zusammenfassung Kupfer(II)-bisaminkomplexe der Formel CuL₂X₂ mitX=Cl^– oder NO ₃ ^– undL=Äthylendiamin (en), Tetramethyläthylendiamin (tmn),o-Phenylendiamin (opd) und 2,2-Bipyridyl (bpy) wurden thermogravimetrisch untersucht und die kinetischen Parameter aus den gemessenen, zu den entsprechenden Schritten gehörenden Masseverlustwerten unter Anwendung der Gleichung von Coats und Redfern bestimmt. Es ergab sich, daß die Aktivierungsenergie dieser Komplexe entsprechend folgender Ligandenreihe abnimmt: bpy > opd > en > tmn. Dies kann bei den bpy und opd Liganden auf die Starrheit des N-C-C-N Fragmentes und im Falle der tmn Liganden auf eine räumliche Überfülltheit am Stickstoffatom zurückgeführt werden. Die Mehrzahl der Zersetzungsschritte sind komplexer Natur und haben häufig aus den Komplexen stammende Teilgruppen zum Ergebnis. Aufgrund der BeobachtungE _a>H scheint der thermische Zersetzungsvorgang dieser Komplexe durch einen Keimbildungs und -Wachstums mechanismus bestimmt zu werden.

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-() (II) CuL₂X₂, X = , aL= (en), (tmn),o- (opd) 2,2- (bpy). C - . , bpy\s>opd\s>en\s>tmn. N-C-C-N o- . , , . E _a H, , « ».

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A research grant from the University Grants Commission (India) to LSP and a JRF to JKK are thankfully acknowledged.     

Electronic, epr and magnetic studies of Co(II), Ni(II) and Cu(II) complexes with thiosemicarbazone (L1) and semicarbazone (L2) derived from pyrole-2-carboxyaldehyde

Co(II), Ni(II) and Cu(II) complexes are synthesized with thiosemicarbazone (L(1)) and semicarbazone (L(2)) derived from pyrole-2-carboxyaldehyde. These complexes are characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electronic and EPR spectral studies .The molar conductance measurements of the complexes in DMSO correspond to non-electrolytic nature except Co(L1)2(NO3)2 and Ni(L1)2(NO3)2 complexes which are 1:2 electrolytes. All the complexes are of high-spin type. On the basis of spectral studies an octahedral geometry may be assigned for Co(II) and Ni(II) complexes except Co(L1)2(NO3)2 and Ni(L1)2(NO3)2 which are of tetrahedral geometry. A tetragonal geometry may be suggested for Cu(II) complexes.     

4,4'-联吡啶、吡嗪和咪唑桥联铜、镍配合物的合成和磁性

合成了六个含氮杂环桥联配合物: [Ni(salal)2(4,4'-bipy)]n、[Ni(Et-dtp)2(4,4'-bipy)]n、[Cu(acac)2(4,4'-bipy)]n、[Cu(TTA)2(pyz)]n、[Cu(TTa)(Im)]n和[Cu(Im)2]n, 用元素分析、IR、MS、ESR和热重分析对它们的结构和性质作了表征。吡嗪配合物的晶体结构显示, 吡嗪配位于拉伸八面体的轴向位置, 桥联Cu(TTA)2形成一维无限链状结构。变温磁化率表明, 4,4'-联吡啶和吡嗪配合物的磁性遵从Curie-Weiss定律, 分子内没有明显的磁交换作用。咪唑配合物中存在着较强的反铁磁性交换作用, 磁交换常数分别为-75和-107cm^-^1。对4,4'-联吡啶、吡嗪和咪唑传递磁交换的性质作了讨论。     

Synthesis, spectroscopic, and thermal properties of some azomethine complexes of Cu(II), Ni(II), and Pt(II)

Four polydentate azomehines and their mono- and binuclear Pt(II), Cu(II), and Ni(II) complexes were synthesized and characterized. The resulting complexes were characterized by FTIR, magnetic measurements, elemental analysis, conductivity measurements, and thermal analysis. Electronic spectra and magnetic susceptibility measurements sustain the proposed distorted square-planar structures for the copper complexes. The electronic spectra display the characteristic pattern of square-planar stereochemistry for the other complexes. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Azomethine complexes have a similar thermal behavior for the selected metal ions. The decomposition processes as water elimination, chloride anion removal as well as degradation of the organic ligands were observed.     

Synthesis and characterization of three Cu(II), Zn(II), Cd(II) supramolecular complexes bridged by biphenyl 2,2′-dicarboxylate

Three complexes, M₂(bpy)₂(bpdc)₂·xH₂O [M = Cu, x = 0; M = Zn or Cd, x = 2], have been hydrothermally synthesized by 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂bpdc) with 2,2′-bipyridine (bpy) to form binuclear molecules. In each, the two bpdc groups align the two opposing planar [M(bpy)]²⁺ cations. The molecules are connected by C–H⋯O hydrogen bonds, π–π stacking, and C–H⋯π interactions to form three dimensional supramolecular networks. Furthermore, at room temperature, complex 3 exhibits strong photoluminescence.     

Synthesis,characterization and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with pyrral-l-histidinate

The Schiff base ligand, pyrral-l-histidinate(L) and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analysis, mass, molar conductance, IR, electronic, magnetic measurements, EPR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR data show that the ligand is tridentate and the binding sites are azomethine nitrogen, imidazole nitrogen and carboxylato oxygen atoms. Electronic spectral and magnetic measurements indicate tetrahedral geometry for Co(II) and octahedral geometry for Ni(II) and Cu(II) complexes, respectively. The observed anisotropic g values indicate the presence of Cu(II) in a tetragonally distorted octahedral environment. The redox properties of the ligand and its complexes have been investigated by cyclic voltammetry. Thermal decomposition profiles are consistent with the proposed formulations. The powder XRD and SEM studies show that all the complexes are nanocrystalline. The in vitro biological screening effects of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus; fungal species, Aspergillus niger, Aspergillus flavus and Candida albicans by the disc diffusion method. The results indicate that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes were assayed on CT DNA using gel electrophoresis in the presence and absence of H₂O₂.     

Spectroscopic,morphology and electrical conductivity studies on Co(II), Ni(II), Cu(II) and Mn(II)-oxaloyldihydrazone complexes

Cobalt (II), nickel (II), copper (II) and manganese (II) complexes of dihydrazone derived from the condensation of oxaloyldihydrazide with 2-hydroxybenzaldehyde have been synthesized. The dihydrazone ligand/chelates were characterized on the basis of their elemental analyses, spectral (UV–Vis., FT-IR, mass, ¹H NMR), magnetism, thermal (TGA) measurements and structures of the compounds have been established. The surface morphology of the desired complexes was studied by SEM. The ligand is coordinated to the Ni(II), Co(II), Mn(II) and Cu(II) centers in bi, tetra, penta and hexadentate way giving mono-nuclear complexes except in case of manganese and copper the bi-nuclear complexes were formed. The nickel complex has tetrahedral geometry while the other complexes are suggested to have octahedral configurations. The prepared samples have been assayed for their electrical activities. The electrical activity (DC and AC conductivity) for ligand and its metal complexes has been examined at different frequencies (1, 10, 100 kHz) in the temperature ranges 303–573 and 300–625 K, respectively. The DC and AC conductivity are viewed as thermally activated process at higher temperatures and a marked increment was seen in case of Mn(II) complex. The dielectric permittivity was determined in the temperature area of 300–625 K and diminished with augmentation of frequency proposing a typical behavior of dielectrics.     

Synthesis, thermal and other studies of 2,4'-bipyridine-dichloroacetato complexes of Mn(II), Co(II), Ni(II) and Cu(II)

Four new mixed ligand complexes were prepared by the reaction of title metal dichloroacetates and 2,4'-bipyridine. The general formulae of synthesized compounds are M(2,4'-bpy)₂(CCl₂HCOO)₂·nH₂O (where M(II)=Mn, Co, Ni, Cu; 2,4'-bpy=2,4'-bipyridine, n=2 or 4). The complexes have been isolated from aqueous media and characterized by chemical analysis, molar conductance (in MeOH, DMSO and DMF), magnetic, IR and VIS spectral studies. The nature of metal(II)-ligand coordination is discussed. The thermal behaviour of obtained complexes was studied by thermal analysis and TG-MS techniques in air. IR, X-ray powder diffraction and thermoanalytical data were used for the determination of solid intermediate products of the thermal decomposition. The principal volatile products of thermal decomposition of complexes were proved by mass spectroscopy: H₂O⁺, CO⁺ ₂, HCl⁺ ₂, Cl⁺ ₂, NO⁺ and other. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis, spectral, thermal and magnetic studies of Mn(II), Ni(II) and Cu(II) complexes with some benzopyran-4-one Schiff bases

The Schiff bases of N(2)O(2) dibasic ligands, H(2)La and H(2)Lb are prepared by the condensation of ethylenediamine (a) and trimethylenediamine (b) with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one. Also tetra basic ligands, H(4)La and H(4)Lb are prepared by the condensation of aliphatic amines (a) and (b) with 6-formyl-5,7-dihydroxy-2-methylbenzopyran-4-one. New complexes of H(4)La and H(4)Lb with metal ions Mn(II), Ni(II) and Cu(II) are synthesized, in addition Mn(II) complexes with ligands H(2)La and H(2)Lb are also synthesized. Elemental and thermal analyses, infrared, ultraviolet-visible as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The structures of copper(II) complexes are also assigned based upon ESR spectra study. All the complexes separated with the stoichiometric ratio (1:1) (M:L) except Mn-H(4)La and Mn-H(4)Lb with (2:1) (M:L) molar ratio. In metal chelates of the type 1:1 (M:L), the Schiff bases behave as a dinegative N(2)O(2) tetradentate ligands. Moreover in 2:1 (M:L) complexes, the Schiff base molecules act as mono negative bidentate ligand and binuclear complex is then formed. The Schiff bases were assayed by the disc diffusion method for antibacterial activity against Staphylococcus aureus and Escherichia coli. The antifungal activity of the Schiff bases was also evaluated against the fungi Aspergillus flavus and Candida albicans.     

Spectrothermal studies of 1,10-phenanthroline complexes of Co(II), NI(II), Cu(II) and Cd(II) orotates

The 1,10-phenanthroline (phen) complexes of Co(II), Ni(II), Cu(II) and Cd(II) orotates were synthesized and characterized by elemental analysis, magnetic susceptibility, spectral methods (UV-vis and FTIR) and thermal analysis techniques (TG, DTG and DTA). The Co(II), Ni(II), Cu(II) and Cd(II) ions in diaquabis(1,10-phenanthroline)metal(II) diorotate octahedral complexes [M(H₂O)₂(phen)₂](H₂Or)₂·nH₂O (M=Co(II), n=2.25; Ni(II), n=3; Cu(II) and Cd(II), n=2) are coordinated by two aqua ligands and two moles of phen molecules as chelating ligands through their two nitrogen atoms. The monoanionic orotate behaves as a counter ion in the complexes. On the basis of the first DTG_max, the thermal stability of the hydrated complexes follows the order: Cd(II), 68°C 68°C     

Spectrothermal studies on Co(II), Ni(II), Cu(II) and Zn(II) salicylato (1,10-phenanthroline) complexes

The cobalt, nickel, copper and zinc atoms in bis(1,10-phenanthroline)bis(salicylato-O)metal(II) monomeric octahedral complexes [M(Hsal)₂(phen)₂]·nH₂O, (M: Co(II), n=1; Cu(II), n=1.5 and Ni(II), Zn(II), n=2) are coordinated by the salicylato monoanion (Hsal) through the carboxyl oxygen in a monodentate fashion and by the 1,10-phenanthroline (phen) molecule through the two amine nitrogen atoms in a bidentate chelating manner. On the basis of the DTG_max, the thermal stability of the hydrated complexes follows order: Ni(II) (149°C)>Co(II) (134°C)>Zn(II) (132°C)>Cu(II) (68°C) in static air atmosphere. In the second stage, the pyrolysis of the anhydrous complexes takes place. The third stage of decomposition is associated with a strong exothermic oxidation process (DTA curves: 410, 453, 500 and 450°C for the Co(II), Ni(II), Cu(II) and Zn(II) complexes, respectively). The final decomposition products, namely CoO, NiO, CuO and ZnO, were identified by IR spectroscopy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Syntheses and spectrothermal studies of triethanolamine complexes of Co(II), Ni(II), Cu(II) and Cd(II) squarates

The triethanolamine complexes, [M(tea)₂]sq·nH₂O, (n=2 for Co(II), n=0 for Ni(II), Cu(II) and n=1 for Cd(II), tea=triethanolamine, sq²⁻=squarate), have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements, UV-Vis and IR spectra, and thermal analyses techniques (TG, DTG and DTA). The Co(II), Ni(II) and Cu(II) complexes possess octahedral geometry, while the Cd(II) complex is monocapped trigonal prismatic geometry. Dianionic squarate behaves as a counter ion in the complexes. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) release of the tea ligands and (iii) burning of organic residue. On the basis of the first DTG_max of the decomposition, the thermal stability of the anhydrous complexes follows the order: Ni(II), 289°C>Co(II), 230°C>Cu(II), 226°C>Cu(II), 170°C in static air atmosphere. The final decomposition products — the respective metal oxides — were identified by FTIR spectroscopy.     

Synthesis and structural studies of complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with substituted chalcones

Complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 3-(2-pyridyl)-1-(2-hydroxy phenyl)-2-propen-1-one (PHPO), 3-(1-naphthyl)-1-(2-hydroxy phenyl)-2-propen-1-one (NHPO) and 3-(3,4-dimethoxy phenyl)-1-(2-hydroxy phenyl)-2-propen-1-one (DMPHPO) have been synthesized and characterized by analytical, conductivity, thermal, magnetic, infrared, electronic and electron spin resonance data. Based on analytical data the stoichiometry of the complexes has been found to be 1 : 2. The conductivity data show that all these complexes are non-electrolytes. The infrared spectral data indicate that the ligand PHPO acts as uninegative tridentately towards Co(II) and Ni(II) and bidentately with Cu(II), Zn(II) and Cd(II). Ligands like NHPO and DMPHPO act as uninegative bidentately with all the metal ions. The electronic spectral data suggest that all the Co(II) complexes and Ni(II) of PHPO complex are octahedral and all the Cu(II) and Ni(II) of NHPO and DMPHPO complex are square-planar. The complex of Zn(II) and Cd(II) are tetrahedral. ESR parameters of Cu(II) complexes have been calculated and relevant conclusions have been drawn with respect to the nature of bonds present in them.