Cobalt(II), nickel(II) and copper(II) complexes of bidentate bibenzimidazoles

Complexes of cobalt(II), nickel(II) and copper(II) with novel bidentate bibenzimidazoles, [M(L-L)Cl2], where L-L are methylenebis(1, 1prime-benzimidazole), methylenebis(2, 2prime-benzimidazole) and dimethylenebis(2, 2prime-benzimidazole) are described and characterized by different physical measurements. The four coordinate complexes have distorted tetrahedral or square coplanar structures. The bridging entity between the two donor groups apparently influences the ligand field strength and the ligands occupy a higher position than that of benzimidazole in the spectrochemical series.

Direct Writing of Copper Film Patterns by Laser-Induced Decomposition of Copper Acetate

Direct writing of patterns is being widely attempted in the field of microelectronic circuit/device manufacture. Use of this technique eliminates the need for employing photolithographic process. Laser induced direct writing can be achieved by (i) Photochemical reaction [i] , (ii) Evaporation from target material [2], and (iii) decomposition.Micron size features of palladium and copper through decomposition of palladium acetate and copper formate respectively on quartz and silicon using Argon ion laser have been reported [3,4] .In this commuication we report a technique for both single line and large area depositon of copper through decomposition of copper acetate,(CH3COO)2Cu, on alumina substrates.Nd:YAG laser known for its reliability and low maintenance cost as compared to excimer and other gas lasers is used. This technique offers an attractive and economical alternative for manufacture of thin film microcircuits.

Fractional-factorial design of a porous-carbon fuel-cell electrode

The use of fractional-factorial methods in the optimization of porous-carbon electrode structure is discussed with respect to weight-loss of carbon during gas treatment, weight and mixing time of binder, compaction temperature, time and pressure, and pressure of feed gas. The experimental optimization of an air electrode in alkaline solution is described.

High-temperature superconductivity in bismuth-copper oxides of the type BimMnCupOx (M=Mg, Ca, Sr, Ba, Bi)

Several oxides of the Bi m M n Cu p O x family (m=2, 3;n=2, 3, 4;p=1, 2, 3 and M=alkaline earth or Bi), possessing structures similar to the Aurivillius family of oxides, show highT c superconductivity.

Magnetic susceptibility studies on ternary oxides of copper(II)

The magnetic susceptibilities of a large number of ternary oxides of copper having structural features common to the presently identified phases of high-temperature superconductors have been studied in the temperature range 14-300 K. The systems studied are Ln2CuOP( Ln = La, Pr, Nd, etc.), Sr2CuO2CI2,B i2Cu0,, Ca2Cu03,S r2Cu03,S rCu02, MgCu203,B a2Cu3O4CI2Y, 2Cu205,Y2BaCu0,, BaCu02, Li2Cu02, etc. Cu2+ ions take different coordinations, like isolated square planar, square pyramidal or distorted-tetrahedral and octahedral, in these compounds. These compounds also exhibit different varieties of possible magnetic superexchange interactions like 180' or 90' Cu-0-Cu or Cu-0-0-Cu types as well as direct Cu-Cu interactions. Compounds in which there are extended 180' Cu-0-Cu interactions show a low, nearly temperature-independent susceptibility (100 X lod emu/mol). The estimated value of J for the Cu-0-Cu interaction is between 800 and 1500 K in these compounds. Isolated Cu2+ ions in which there are no 180' or close to 180" Cu-0-Cu interactions show Curie-Weiss susceptibility behavior. Compounds with only Cu-0-0-Cu interaction show evidence for the onset of antiferromagnetic coupling between 30 and 50 K. The superexchange rules are useful for explaining the qualitative features of the results. The possibility of disproportionation of Cu2+ ion when there are short Cu-Cu distances as in Bi2Cu04 is discussed. The extended geometry of the copper-oxygen framework seems to be more important than the local geometry around the Cu2+ ion in determining the magnetic properties.

Nature of the copper species in superconducting YBa2Cu3O7

The nominal composition of YBa2Cu3O7 oxide suggests that 33% of the copper should be in the 3+ state. In structural studies3–5, Cu3+ and Cu2+ ions have been assigned specific sites based on their preferred coordinations, and many of the models of superconductivity also require the presence of Cu3+. Our studies however show that Cu is present only in the Cu1+ and Cu2+ states, the proportion of the former increasing with decreasing temperature. It appears that there is no clear experimental evidence for the presence of Cu3+ in YBa2Cu3O7.

Intermolecular Chelate Linkage Isomerism of the Hydroxyimino Group in the Nickel(II), Copper(II), and Palladium(II) Complexes of Quadridentate Schiff-base Ligands

The C-nitrosation of bivalent quadridentate β-imino ketone complexes of nickel(II), copper(II), and palladium(II), with nitrosating reagents has been investigated. The chemical analysis and spectroscopic results reveal that one of the α-CH groups of the coordinated lignad undergoes selective nitrosation forming mono(hydroxyimino) derivative. The hydroxyimino group introduced coordinates through either N- or O- atom to metal(II) by dislodging the carbonyl group already coordinated. This gives rise to two linkage isomers, one with N-bonded and the other with O-bonded hydroxyimino group in the case of nickel(II) (except for 1d) and palladium(II), and a single isomer with O-bonded hydroxyimino group in copper(II) complexes. The isomers obtained from 1b and 1i have been separated by column chromatography. In chloroform each of the isomers of nickel(II) isomerizes to give an equilibrium mixture of two isomers, but not those of copper(II) and palladium(II).

Electron paramagnetic resonance studies of some ternary oxides of copper (II)

The electron paramagnetic resonance (EPR) of ternary oxides of Cu(II) has been studied between 4.2 and 300 K. The systems include those with 180 degrees Cu-O-Cu interactions (such as Ln2CuO4, Sr2CuO2Cl2, Sr2CuO3 and Ca2CuO3) or 90 degrees Cu-O-Cu interactions (such as Y2Cu2O5 or BaCuO2) as well as those in which the Cu2+ ions are isolated (such as Y2BaCuO5, La1.8Ba1.2Cu0.9O4.8 and Bi2CuO4). The change in the EPR susceptibility as a function of temperature is compared with that of the DC magnetic susceptibility. Compounds with extended 180 degrees Cu-O-Cu interactions which have a low susceptibility also do not give EPR signals below room temperature. For compounds such as Ca2CuO3 with one-dimensional 180 degrees Cu-O-Cu interactions a weak EPR signal is found the temperature dependence of which is very different from that of the DC susceptibility. For Y2BaCuO5 as well as for La1.8Ba1.2Cu0.9O4.8 the EPR susceptibility as well as its temperature variation are comparable with those of the static susceptibility near room temperature but very different at low temperatures. Bi2CuO4 also shows a similar behaviour. In contrast, for Y2Cu2O5, in which the copper ions have a very distorted nonsquare-planar configuration, the EPR and the static susceptibility show very similar temperature dependences. In general, compounds in which the copper ions have a square-planar geometry give no EPR signal in the ground state (0 K) while those with a distortion from square-planar geometry do give a signal. The results are analysed in the light of recent MS Xalpha calculations on CuO46- square-planar clusters with various Cu-O distances as well as distortions. It is suggested that in square-planar geometry the ground state has an unpaired electron in anionic orbitals which is EPR inactive. Competing interactions from other cations, an increase in Cu-O distance or distortions from square-planar geometry stabilise another state which has considerably more Cu 3d character. These states are EPR active. Both these states, however, are magnetic. For isolated CuO46- clusters the magnetic interactions seem to involve only the states which have mainly anionic character.

Effect of isonicotinic acid hydrazide-copper complex on Rous sarcoma virus and its genome RNA

The copper complex of the antituberculous drug, isonicotinic acid hydrazide (INH), inhibits the RNA-dependent DNA polymerase of Rous sarcoma virus and inactivates its ability to malignantly transform chick embryo cells. The INH-copper complex binds to the 70S genome RNA of Rous sarcoma virus (RSV), which may account for its ability to inhibit the RNA-dependent DNA polymerase. The complex binds RNA more effectively than DNA in contrast to M-IBT-copper complexes, which bind both types of nucleic acids equally. The homopolymers, poly rA and poly rU, are bound by the INH-copper complex to a greater extent than poly rC. Isonicotinic acid hydrazide alone and CuSO4 alone bind neither DNA, RNA, poly (rA), poly (rU), nor poly (rC). However, CuSO4 alone binds poly (rI); INH alone does not. In addition to viral DNA synthesis, chick-embryo cell DNA synthesis is inhibited by the INH-copper complex. The extent of inhibition of cellular DNA synthesis is greater than that of cellular RNA and protein synthesis. No selective inhibition of transformation in cells previously infected with Rous sarcoma virus is observed.

Electrochemical reduction of Cu(II)-CyDTA complex at dropping mercury electrode. An impedance approach

The electrochemical reduction of Cu(II)-CyDTA (CyDTA — trans 1,2-cyclohexanediamine N, N, N′, N′ tetraacetic acid) by impedance method reveals the unusual behaviour of complex plane polarograms owing to potential dependence of double layer capacitance. The impedance plane plots by frequency variation method indicates the quasi-reversible nature of the system. From these plots the chargetransfer resistance at various potentials was evaluated. The standard rate constant was evaluated which complements the prediction of impedance plots for the quasireversible behaviour of the system.

DNA photocleavage and anticancer activity of terpyridine copper(II) complexes having phenanthroline bases

Copper(II) complexes Cu(ph-tpy)(B)](ClO4) (1-3), where ph-tpy is (4'-phenyl)-2,2':6',2 `'-terpyridine and B is N,N-donor phenanthroline base, viz. 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and characterized from analytical and spectral data. Complex 1, characterized by X-ray crystallography, shows a distorted square-pyramidal (4 + 1) CuN5 coordination geometry having the tridentate ph-tpy ligand at the basal plane and bidentate phen bound to the axial-equatorial sites. The complexes display a d-d band near 650 nm in aqueous DMF. The complexes are avid binders to calf thymus DNA giving the binding order: 3 (dppz) > 2 (dpq) > 1 (phen). The dpq and dppz complexes show photo-induced DNA cleavage activity in red light via photo-redox pathway forming hydroxyl radicals. The cytotoxicity of the dppz complex 3 was studied by MTT assay in HeLa cancer cells. The IC50 values are 3.7 and 12.4 mu M in visible light of 400-700 nm and dark, respectively. (C) 2010 Elsevier Ltd. All rights reserved.

Electrochemical reduction of Cu(II)-EDTA complex at dropping mercury electrode. An impedance approach

The study of electrochemical reduction of Cu(II)-EDTA system by phase sensitive a.c. impedance method at dropping mercury electrode reveals several interesting features. The complex plane polarograms exhibit loop like shape in contrast to the classical zinc ion reduction where crest like shape is found. Again, the relative placement of peaks of in-phase and quadrature components, and the relative placement of portions before and after the peaks of complex plane polarograms are different from that of zinc ion reduction. The complex plane plots suggest that electrochemical reduction of Cu-EDTA is charge transfer controlled.

Electrophilic Substitution Reactions of Copper(II) Acetylacetoneimine Complexes with Arene Diazonium Ions

Copper(II) complexes of ethylene/propylene-bis(acetylacetoneimine), Cu(baen) or Cu(bapn), react quickly and quantitatively in aqueous methanol at the methine position with arene diazonium ions in a stepwise manner to yield mono- and di-substituted copper(II) complexes. All the complexes are paramagnetic with μeff∼1.88 B.M. In all the complexes the diazo substituted part of the ligand coordinates to the metal through the agr-nitrogen of the azo group and the imine nitrogen, forming glyoxaliminearylhydrazone type of ligand system. The complexes have been characterized by elemental analysis, electronic, esr, ir and mass spectroscopic methods.