Thermal Studies on Energetic Compounds

The nitrate complexes of copper, nickel and zinc with diethylenetriamine (dien) i.e. [Cu(dien)₂](NO₃)₂, [Ni(dien)₂](NO₃)₂·2H₂O and [Zn(dien)₂](NO₃)₂ have been prepared and characterised. Thermal studies were undertaken using TG-DTG, DSC, ignition delay (t _id) and ignition temperature (IT) measurements. Impact sensitivity was measured using drop mass technique. The kinetic parameters for both non-isothermal and isothermal decomposition of the complexes were evaluated by employing Coats-Redfern (C-R) method and Avrami-Erofeev (A-E) equations (n=2 and 3), respectively. The kinetic analysis, using isothermal TG data, was also made on the basis of model free isoconversional method and plausible mechanistic pathways for their decomposition are proposed. Rapid process was assessed by ignition delay measurements. All these complexes were found to be insensitive towards impact of 2 kg mass hammer up to the height limit (110 cm) of the instrument used. The heat of reaction (?H) for each stage of decomposition was determined using DSC.     

Zinc(II), Cobalt(II) and Nickel(II) Complexes of 5-Substituted-1,3,4-Thiadiazoles

Zn(II), Co(II) and Ni(II) complexes with some 5-substituted-1,3,4-thiadiazoles (L₁-L₄) have been prepared and characterized by conductivity, microanalysis, thermal analysis, infrared and electronic spectra measurements. All complexes behave as 1:1 electrolyte and the ligands are coordinated as bidentate molecules. The stability constants and energy of formation are determined and discussed on the basis of the ligands structure.     

Cobalt,Nickel and Copper Complexes of Benzylamino-p-chlorophenylglyoxime. Thermal and thermodynamic data

Vic-dioxime ligandsand their metal complexes are used in analytical, bio, pigment and medicinal chemistry. Complexes of nickel(II), copper(II), and cobalt(II) with benzylamino-p-chlorophenylglyoxime (BpCPG) are synthesised. Thermal behaviour of these complexes was studied in dynamic nitrogen atmosphere by DTA, DTG and TG techniques. GC-MS combined system was used to identify the products during pyrolytic decomposition. The pyrolytic end products were identified by X-ray powder diffraction. Thermoanalytical data of these complexes are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the integral method using the Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. The metal complexes undergo decomposition in three stages and metal oxides remained as end products of the complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Thermal Stability of Ciprofloxacin Complexes with Magnesium(II), Zinc(II) and Cobalt(II)

The thermal behaviour of Mg(II), Zn(II) and Co(II) compounds of ciprofloxacin was studied by thermogravimetry (TG) and differential thermal analysis (DTA) in order to determine or to confirm some structural characteristics of substances. The complexes decompose in two steps: dehydration and pyrolytic decomposition of the anhydrous complexes to form metal oxide or metal fluoride. The dehydration process of one magnesium(II) compound takes place in two steps suggesting a marked difference in the bonding of water molecules. The different bonding mode of the ciprofloxacin molecules in both magnesium compounds leads to different residues of the thermal decompositions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of the Thermal Decompositions on N,N-Dialkyl-N'-Benzoylthiourea Complexes of Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III)

The thermal decompositions of the complexes of N,N-dialkyl-N'-benzoylthioureas with Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III) were studied by TG and DTA techniques. These metal complexes decompose in two stages: elimination of dialkylbenzamide, and total decomposition to metal sulphides or metals. The influence of the alkyl substituents in these benzoylthiourea chelates on the thermal behaviour of the metal complexes was investigated.This revised version was published online in November 2005 with corrections to the Cover Date.     

Cobalt(II), Nickel(II), and Copper(II) Complexes with Diphenylthiocarbazide

New [ML(H₂O)₂] complexes (M = Co²⁺, Ni²⁺, or Cu²⁺; H₂L = diphenylthiocarbazide) were synthesized and studied using IR and diffuse reflection electronic spectroscopy, magnetic chemistry, conductometry, and DTA. The metals were shown to coordinate L^2–through nitrogen and sulfur atoms. The complex [CuL(H₂O)₂] is a dimer.     

Synthesis,Electronic and IR Spectral Studies of Some Polymeric Cobalt(II), Nickel(II), Zinc(II) and Cadmium(II) Azido Complexes with Hydrazine

A series of polymeric cobalt(II), nickel(II), zinc(II) and cadmium(II) azido complexes with hydrazine of the type [M(N₂H₄)(H₂O)(N₃)Cl]_n, [M(N₂H₄)(N₃)₂]_n and [M(N₂H₄)₂(N₃)₂]_n have been prepared. These were characterized by elemental analyses, magnetic susceptibility measurements, electronic and IR spectra. The complexes are highly insoluble in polar and non polar solvents. All the complexes decompose with explosion at different temperatures between 100°C to 200°C. The magnetic moment and electronic spectral data for Co(II) and Ni(II) complexes suggest that the complexes have octahedral structure. The ligand-field parameters (10 Dq, B, β, β° and LFSE) have also been calculated for all Co(II) and Ni(II) complexes which indicate a significant covalent character of M-L bonds. The IR spectra of the complexes show that the azide group and hydrazine molecule both act as bidentate bridging ligands in [M(N₂H₄)(H₂O)(N₃)Cl]_n and [M(N₂H₄)(N₃)₂]_n type complexes but the azide group is terminally bonded to metal in all [M(N₂H₄)₂(N₃)₂]_n type complexes.     

Stability of Copper(II), Nickel(II) and Zinc(II) Binary and Ternary Complexes of Histidine,Histamine and Glycine in Aqueous Solution

The binary and mixed-ligand complexes formed between ligands (histidine (His), histamine (Him) and glycine (Gly)) and some transition metals (Cu(II), Ni(II) and Zn(II)) were studied potentiometrically in aqueous solution at (25.0 ± 0.1) C and I = 0.10 M KCl in order to determine the protonation constants of the free ligands and stability constants of binary and ternary complexes. The complexation model for each system has been established by the software program BEST from the potentiometric data. The most probable binding mode for each binary species of histidine and for all mixed species was also discussed based upon derived equilibrium constants and stability constants related to the binary species. The ambidentate nature of the histidine ligand, i.e. the ability to coordinate histamine-like, imidazolepropionic acid-like and glycine-like modes was indicated from the results obtained. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters, log K, log X and ₁₁₁₀. The concentration distributions of various species formed in solution were also evaluated. In terms of the nature of metal ion, the complex stability follows the trend Cu(II) > Ni(II) > Zn(II), which is in agreement with the Irving-Williams order of metal ions. Thus, the results obtained were compared and evaluated with those in the literature.     

Novel Cobalt(II), Nickel(II) and Copper(II) Complexes of Neutral Orotic Acid. Synthesis,Spectroscopic and Thermal Studies

The new orotic acid complexes, [MCl₂(H₂O)₃(H₃Or)], M=Co(II), Ni(II) and [CuCl₂(H₂O)(H₃Or)₃] · H₂O, were synthesized and characterized by elemental analysis, magnetic susceptibility, spectral (Diffuse reflectance UV–Vis and FTIR) methods, and simultaneous thermal analysis (TG, DTG and DTA) techniques. Physical measurements indicate that the neutral orotic acid ligands are bonded to metal ions through the carbonyl groups. Two thermal processes of the complexes can occur: dehydration and pyrolytic decomposition. On the basis of the DTG_max, the thermal stability of the complexes follows the order: Co(II) (122 °C) > Cu(II) (77 °C) > Ni(II) (66 °C).     

四氮大环-金属配合物与DNA作用的电化学及谱学研究

Mononuclear copper（Ⅱ）, nickel（Ⅱ） and cobalt（Ⅲ） tetracoordinate macrocyclic complexes were synthesized and spectroscopically characterized. The crystal structure of the three compounds were determined by X-ray crystallography. The electrochemical experimental results indicate that the three complexes could interact with DNA mainly by electrostatic interaction. The interaction of tetracoordinate macrocyclic cobalt（Ⅲ） complex with DNA was studied by cyclic voltammetry and UV-vis spectroscopy. The experimental results reveal that tetracoordinate macrocyc- lic cobalt（Ⅲ） complex could interact with DNA by electrostatic interaction to form a 1 ： 1 DNA association complex with a binding constant of 7.50 ×10^3 L·mol^-1.     

N-Formamid osalicylaldimine andN-Acetamidosalicylaldimine Complexes of Copper(II), Nickel(II) and Cobalt(II)

Summary N-formamidosalicylaldimine (H₂SF) andN-acetamidosalicylaldimine (H₂SA) complexes of Cu^II, Ni^II and Co^II have been synthesized and characterized by analytical, spectroscopic and magnetic data. The ligands coordinate to the metalvia the hydroxyl, carbonyl and imino groups to yield normal paramagnetic and insoluble complexes which decompose above 250°.     

Syntheses,Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn²⁺, Cu²⁺, Pt²⁺ and Ni²⁺ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by ¹H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn²⁺ and Pt²⁺ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn²⁺, Cu²⁺ and Ni²⁺ complexes) and by emission titrations (for one Pt²⁺ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.     

Synthesis and Physicochemical Study of Iron(II), Cobalt(II), Nickel(II), and Copper(II) Complexes with 4-(2-Pyridyl)-1,2,4-Triazole

New complexes of iron(II), cobalt(II), and nickel(II) with 4-(2-pyridyl)-1,2,4-triazole (PyTrz), [Fe₃(PyTrz)₈(H₂O)₄]A₆ (A = NO₃ ^-, ClO₄ ^-, Br^-) and [M₃(PyTrz)₈(H₂O)₄](NO₃)₆ (M = Co, Ni), were synthesized and studied by X-ray diffraction, magnetochemical method, and electronic and IR spectroscopy. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆) was also studied by adiabatic calorimetry. The Fe(II), Co(II), and Ni(II) nitrate complexes were shown to be isostructural to the previously synthesized linear trinuclear [Cu₃(PyTrz)₈H₂O)₄](NO₃)₆ complex. In all compounds, antiferromagnetic exchange interactions between M²⁺ ions were detected. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆ undergoes the ¹ A ₁ ⁵ T ₂ spin transition.     

Complexes of Cobalt(II), Nickel(II) and Copper(II) Chloroacetates with Quinoline N-Oxide

Some 1:1 and 1:2 adducts of cobalt(II), nickel(II) and copper(II) chloroacetates with quinoline N -oxide have been isolated by the interaction of the appropriate metal chloroacetate with quinoline N -oxide (QuinNo). The complexes isolated are of 1:1 stoichiometry of formula (M(CH_3-xCl_xCOO)₂QuinNO) (when M=Co(II), Ni(Il); X=l, 2 and 3 and when M=Cu(II), X=1 and 2) except copper(II) trichloroacetate which yields an adduct of 1:2 stoichiometry of formula[Cu(CCl₃COO)₂ (QuinNO)₃]. The adducts isolated are soluble in common organic solvents.     

Complexes of Cobalt(II), Nickel(II) and Copper(II) Chloroacetates with Quinoline N-Oxide

Some 1:1 and 1:2 adducts of cobalt(II), nickel(II) and copper(II) chloroacetates with quinoline N -oxide have been isolated by the interaction of the appropriate metal chloroacetate with quinoline N -oxide (QuinNo). The complexes isolated are of 1:1 stoichiometry of formula [M(CH₃_xClxCOO)₂QuinNO] (when M=Co(II), Ni(II); X=1,2 and 3 and when M=Cu(II), X=l and 2) except copper(II) trichloroacetate which yields an adduct of 1:2 stoichiometry of formula[Cu(CCI₃COO)₂(QuinNO)₂]. The adducts isolated are soluble in common organic solvents.     

Copper(II), Nickel(II) and Cobalt(II) Complexes of Dibasic Tridentate Schiff Bases

Complexes of Cu(II), Ni(II) and Co(II) with the Schiff bases derived from o-aminobenzoic acid with salicylaldehyde and its 5-chloro and 5-bromo derivatives have been prepared. The 1:1 (metal-ligand) stoichiometry of these complexes is shown by elemental analysis, gravimetric estimations and conductometric titrations while the structures of the complexes are proved by i.r. spectra and thermogravimetric analysis. The magnetic susceptibility and electronic spectra of Cu(II) complexes indicate the nonplanar binuclear structures while that of Ni(II) and Co(II) show their paramagnetic octahedral geometry. The molar conductance values in nitrobenzene indicate the nonelectrolytic behaviour of the complexes. The results show that the complexes of the type (Cu·L)₂, Ni·L·3H₂O and Co·L·3H₂O are formed having solvent molecule in coordination with the metal ion. The monopyridine and monoammonia adducts of Cu(II) complexes were found to be monomeric.     

New Copper（Ⅱ） and Nickel（Ⅱ） Complexes of 4-Morpholinoacetophenone Thiosemicarbazone： Structural, Electrochemical and Antimicrobial Studies

4-Morpholinoacetophenone thiosemicarbazone, MAPT, and its nickel（Ⅱ） and copper（Ⅱ） complexes have been prepared and characterized by elemental analysis, magnetic susceptibility, spectral methods （FT-IR, ^1H NMR） and cyclic voltammetry. Electrochemical behaviors of the complexes have been studied by cyclic voltammetry in DMF media showing metal centered reduction processes for both of them. The redox properties, nature of the electrode processes and the stability of the complexes were discussed. [Cu（MAPT）2]Cl2 complex shows Cu（Ⅱ）/Cu（Ⅰ） couple and quasi-reversible wave associated with the Cu（Ⅲ）/Cu（Ⅱ） process. The reduction/oxidation potential values depend on the structures of complexes. Also, the antimicrobial activities of these complexes were determined against S. aureus, E. coli and B. subtilis.     

Thermal Studies of Copper(II) Squarate Complexes of Diamines in the Solid State

CuL₂C₄O₄ [L=ethane-1,2-diamine (en)], CuL₂C₄O₄⋅2H₂O [L=N-methylethane-1,2-diamine (meen), N-ethylethane-1,2-diamine (eten),N-propylethane-1,2-diamine (pren), N-methyl-N’-ethylethane- 1,2-diamine (meeten) andpropane-1,2-diamine (pn)], CuL₂C₄O₄⋅0.5H₂O [L=N,N’-dimethylethane- 1,2-diamine (dmeen)], CuL₂C₄O₄⋅4H₂O [L=propane-1,2-diamine (pn)]and CuL₂C₄O₄⋅H₂O[L=2-methylpropane-1,2-diamine (ibn)] have been synthesized by the addition of respective diamine to finely powdered CuC₄O₄⋅2H₂O and their thermal studies have been carried out in the solid state. Cu(en)₂C₄O₄ upon heating loses one molecule of diamine with shar pcolour change yielding Cu(en)C₄O₄ which upon further heating transforms to unidentified products. All aquated-bis-diamine species [CuL₂C₄O₄⋅2H₂O, CuL₂C₄O₄⋅0.5H₂O and CuL₂C₄O₄⋅H₂O] upon heating undergo deaquation–anation reaction in the solid state showing thermochromism and transform to CuL₂C⁴O₄, which revert on exposure to humid atmosphere (RH ∼90%). All the squarato bis-diamine species, CuL₂C₄O₄, on further heating transform to unidentified products through the formation of CuLC₄O₄ as intermediates. The mono diamine species, have been isolated pyrolytically in the solid state and can be stored in a desiccator as well as in open atmosphere. They are proposed to be polymeric. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Studies on Some Biologically Active Organomercury(II) Complexes

Thermal behaviour of a number of organomercury(II) complexes of the type, p-XC₆H₄HgCl(L¹) (I), p-XC₆H₄HgCl₃(L²) (II), p-XC₆H₄HgL³ (III) and p-XC₆H₄HgL⁴ (IV) [L ¹=isoniazid, L ²=theobromine, L ³=phenyldithiocarbamate, L ⁴=p-nitrophenyldithiocarbamate; X=Me, MeO, NO₂] has been investigated. From TG curves, the order and activation energy of the thermal decomposition reaction have been elucidated. The variation of the activation energy has been correlated with the nature of the substituent on the phenyl ring. The heat of reaction has been elucidated from DSC or DTA studies. The fragmentation pattern has been analysed on the basis of mass spectra.This revised version was published online in November 2005 with corrections to the Cover Date.A part of this work was carried out at Intitute of Microbial Technology, Chandigarh, under the Visiting Associateship Scheme (1992–95) of the Council of Scientific and Industrial Research, New Delhi.     

Polymer Supported Schiff Base Complexes of Iron(III), Cobalt(II) and Nickel(II) Ions and their Catalytic Activity in Oxidation of Phenol and Cyclohexene

The polymer supported transition metal complexes of N,N′‐bis (o‐hydroxy acetophenone) hydrazine (HPHZ) Schiff base were prepared by immobilization of N,N′‐bis(4‐amino‐o‐hydroxyacetophenone)hydrazine (AHPHZ) Schiff base on chloromethylated polystyrene beads of a constant degree of crosslinking and then loading iron(III), cobalt(II) and nickel(II) ions in methanol. The complexation of polymer anchored HPHZ Schiff base with iron(III), cobalt(II) and nickel(II) ions was 83.30%, 84.20% and 87.80%, respectively, whereas with unsupported HPHZ Schiff base, the complexation of these metal ions was 80.3%, 79.90% and 85.63%. The unsupported and polymer supported metal complexes were characterized for their structures using I.R, UV and elemental analysis. The iron(III) complexes of HPHZ Schiff base were octahedral in geometry, whereas cobalt(II) and nickel(II) complexes showed square planar structures as supported by UV and magnetic measurements. The thermogravimetric analysis (TGA) of HPHZ Schiff base and its metal complexes was used to analyze the variation in thermal stability of HPHZ Schiff base on complexation with metal ions. The HPHZ Schiff base showed a weight loss of 58% at 500°C, but its iron(III), cobalt(II) and nickel(II) ions complexes have shown a weight loss of 30%, 52% and 45% at same temperature. The catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in presence of hydrogen peroxide as an oxidant. The supported HPHZ Schiff base complexes of iron(III) ions showed 64.0% conversion for phenol and 81.3% conversion for cyclohexene at a molar ratio of 1∶1∶1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 55.5% conversion for phenol and 66.4% conversion for cyclohexene at 1∶1∶1 molar ratio of substrate to catalyst and hydrogen peroxide. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 90.5% and 96.5% with supported HPHZ Schiff base complexes of iron(III) ions, but was found to be low with cobalt(II) and nickel(II) ions complexes of Schiff base. The selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was different with studied metal ions and varied with molar ratio of metal ions in the reaction mixture. The selectivity was constant on varying the molar ratio of hydrogen peroxide and substrate. The energy of activation for epoxidation of cyclohexene and phenol conversion in presence of polymer supported HPHZ Schiff base complexes of iron(III) ions was 8.9 kJ mol^?1 and 22.8 kJ mol^?1, respectively, but was high with Schiff base complexes of cobalt(II) and nickel(II) ions and with unsupported Schiff base complexes.