Thermal analysis of heterocyclic thione donor complexes. Part III. Cobalt(II) complexes of imidazolidine-2-thione

The thermal decomposition of the cobalt(II) complexes of imidazolidine-2-thione (Imdt), Co(Imdt)₂X₂ (X = Cl, Br, and I) have been studied in air and argon by means of TG and DTG as well as in nitrogen by DTA. Decomposition schemes have been proposed for the complexes in both air and inert atmospheres. Reaction enthalpies have been derived from the melting and decomposition endotherms by means of quantitative DTA. A mean coordinate bond dissociation energy, D?, has been estimated for the Co-Imdt bond in the chloro complex. Reaction products in air have been identified by X-ray powder diffraction.     

Thermal study of ruthenium(II) complexes containing pyridine-2,6-diimines

Thermal behaviors of mono-and binuclear Ru(II)-pydim complexes: [PydimCl₂RuL] (Pydim: pyridine-2,6-diimine; 2: L=NCMe; 3: L=PPh₃) and [PydimCl₂Ru(L-L)RuCl₂Pydim] (4: L-L=pyrazine; 5: L-L=4,4′-bipyridine) have been studied in nitrogen atmosphere using TG/DTG and DTA techniques. The decompositions of complexes occur in stepwise. The values of activation energy, E _a, and reaction order, n of the thermal decomposition were calculated by means of several methods such as Coats-Redfern (CR), MacCallum-Tanner (MT), Horowitz-Metzger (HM), van Krevelen (vK), Madhusudanan-Krishnan-Ninan (MKN) and Wanjun-Yuwen-Hen-Cunxin (WYHC) based on the single heating rate. Most appropriate method was determined for each decomposition step according to the least-squares linear regression.     

Thermal analysis of cobalt,nickel and copper complexes of 2-aminothiazole

The thermal decomposition of 2-aminothiazole (2-amt) complexes of general formula M(2-amt)₂X₂ [M = Co(II) and Cu(II)] and Ni(2-amt)₄X₂ [X = Cl and Br] have been studied in air and argon by TG and DTG as well as by DTA in nitrogen; end products from the decompositions in air have been characterised by X-ray powder diffraction. Decomposition stoichiometries have been proposed and factors governing the thermal decomposition have been discussed.     

Thermal decomposition reactions of metal carboxylato complexes in the solid state. I.: Thermographic and differential thermal studies of metal oxalato,malonato and succinato complexes

Thermal investigation of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non-transition metals like Zn(II) and Cd(II) in the solid state has been carried out under non-isothermal conditions in nitrogen atmosphere by simultaneous TG and DTA. TG and DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of the standard potential of the central metal ion. The thermal parameters like activation energy, E_a, enthalpy change, ΔH, and entropy change, ΔS, corresponding to the dehydration and decomposition of the complexes are determined from TG and DTA curves by standard methods. A linear correlation is found between ΔH and ΔS and E_a and ΔS in dehydration and decomposition processes. DTA curves show an irreversible phase transition for Na₂Mn(mal)₂], Na₂[Cu(mal)₂] and Na₂,[Co(suc)₂] complexes. The residual products in these decomposition processes being a mixture of two oxides, of oxide and carbonate or a mixture of two carbonates.     

Studies on energetic compounds part 37: kinetics of thermal decomposition of perchlorate complexes of some transition metals with ethylenediamine

Five bis(ethylenediamine)metal perchlorate (BEMP) complexes like [M(en)₂](ClO₄)₂ (where M=Mn, Co, Ni, Cu, Zn and en=ethylenediamine) have been prepared and characterized by gravimetric methods, infrared spectroscopy (IR) and elemental analysis. Thermal decomposition studies have been undertaken using simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) in nitrogen atmosphere. Non-isothermal TG and DTA studies have also been carried out separately in air to examine the effect of atmosphere on thermolysis of these complexes. Thermal stability of the complexes was found to decrease in the order: [Zn(en)₂](ClO₄)₂>[Mn(en)₂](ClO₄)₂>[Ni(en)₂](ClO₄)₂>[Cu(en)₂](ClO₄)₂>[Co(en)₂](ClO₄)₂.Isothermal TG over the temperature range of decomposition of all these complexes, has been done to evaluate the kinetics of decomposition. Both model fitting and model free isoconversional methods have been used to analyse the kinetics. Isoconversional method has been found to be superior over the conventional model fitting method and is able to describe the complex decomposition of these complexes. It indicates that the values of activation energy vary with the extent of conversion (α) while model fitting method results in a single value of E for overall decomposition process which cannot be attributed to any process under such a complex decomposition reaction. Explosion delay (D_E) measurement has been carried out to investigate the response of these complexes under the condition of rapid heating.     

Thermochemistry of some complexes of chromium(III) with imidazoles

The thermal decomposition in air of several complexes of chromium(III) with imidazole,N-methylimidazole and 2-methylimidazole has been studied with the aid of differential thermal analysis (DTA), thermogravimetry (TG) and derivative thermogravimetry (DTG) in the temperature range 25–600°C. Although the final process of the decomposition gives Cr₂O₃, there are interesting differences in the complete process of decomposition. The reasons for these differences appear to be related to the trans-effect and to the presence in the imidazole complexes of hydrogen bonds. Enthalpies of the several decomposition reactions have been determined by differential thermal analysis.     

Bis[n(chlorophenyl)dithiocarbamato] complexes of Cu(II), Zn(II), Cd(II) and Sn(II)

Ammonium[N(o-chlorophenyl)dithiocarbamate], NH₄(OCD), ammonium [N(m-chlorophenyl)dithiocarbamate], NH₄(MCD) and ammonium [N(p-chlorophenyl)dithiocarbamate], NH₄(PCD) and their complexes with Cu(II), Zn(II), Cd(II) and Sn(II) have been synthesised. These complexes have been characterised on the basis of chemical analyses, molecular weight determinations, conductance measurements, electronic and IR spectral studies. Thermal behaviour of the compounds has been studied with the aid of TG and DTA techniques in static air atmosphere. Heats of reaction for different decomposition steps have been calculated from the DTA curves. The end products obtained after thermal decomposition of the complexes were identified by elemental analyses and IR spectral data.     

Thermal decomposition reactions of metal carboxylato complexes in the solid state: II. Thermographic and differential thermal studies of metal oxalato,malonato and succinato complexes

The thermal investigations of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non transition metals like Zn(II) and Cd(II) in solid state were carried out under non-isothermal condition in nitrogen atmopshere by thermogravimetric (TG) and differential thermal analyses (DTA) methods. The results of DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of standard potential of the central metal ion. The thermal parameters like activation energy (E_a¹), enthalpy change (ΔH) and entropy change (ΔS) corresponding to deaquation, deammoniation and decomposition processes occurred simultaneously or separately were determined from TG and DTA curves by the standard methods. A linear correlation has been found in the plots of ΔH vs. ΔS and E_a¹ vs. ΔS in deaquation, deammoniation and decomposition processes. An irreversible phase transition was noticed for H₂[Mn(suc)₂] and H₂[Co(suc)₂] complexes in DTA curves. The residual pyrolysed products were metal carbonates.     

Studies on the thermal decomposition of salicylhydroxamic acid and its metal complexes with Ni(II), Co(II), Fe(II), Mn(II) and Zn(II)

The thermal decomposition of salicylhydroxamic acid and its metal complexes with Ni(II), Co(II), Fe(II), Mn(II) and Zn(II) has been studied by TG, DTG, DTA and IR spectroscopy. All the compounds investigated decompose to yield intermediate N-hydroxylactams.Decomposition schemes have been proposed and reaction enthalpies and kinetic parameters have been calculated.     

Thermal properties of solid complexes with biologically important heterocyclic ligands

The thermal decomposition of the complexes Mg(SCN)₂(2-OHpy)₄·H₂O(I), Mg(SCN)₂(quin)₄·2H₂O(II) and Mg(SCN)(quinox)₄·5H₂O(III) (2-OHpy–2-hydroxypyridine, quin–quinoline, quinox–quinoxaline) has been investigated in static air atmosphere at 20–1000 °C by means of thermogravimetry (TG), differential thermal analysis (DTA), and infrared (IR) spectroscopy. The composition of the complexes had been identified by means of elemental analysis and complexometric titration. The possible scheme of destruction of the complexes is suggested. The final product of the thermal decomposition was MgS. IR data suggest that heterocyclic ligands were coordinated to Mg(II) through the nitrogen atom of their heterocyclic ring. Thiocyanate group is also coordinated through the nitrogen atom.     

The thermal decomposition of transition-metal complexes containing heterocyclic ligands: I. Benzothiazole complexes

Enthalpies of the decomposition reactions MX₂L₂(c)→MX₂(c) + 2L (g), where M is Mn, Co, Ni, Cu, or Cd, X is Cl and/or Br, and L is benzothiazole or 2-methyl-benzothiazole have been measured by use of a differential scanning calorimeter. Specific heats and enthalpies of sublimation of some of the complexes have been obtained.     

Thermal properties of solid complexes with biologically important heterocyclic ligands

The stoichiometry of thermal decomposition of the complexes Co(NCS)₂(fpy)₄ (I), Co(NCS)₂(Mefpy)₄ (II) and Co(NCS)₂(bfpy)₄ (III) (where fpy = furo[3,2-c]pyridine, Mefpy = methylfuro[3,2-c]pyridine, bfpy = benzo-[2, 3]furo[3,2-c]pyridine) have been investigated in nitrogen atmosphere from room temperature (RT) to 800 °C by means of TG and DTA. The results revealed that release of heterocyclic ligands occurs in one step. Infrared data suggested that fpy, Mefpy and bfpy were coordinated to Co(II) through the nitrogen atom of the respective heterocyclic ring and anionic ligands through nitrogen atom of the NCS groups.     

Tris-Nethyl, m-tolyl)dithiocarbamato complexes of arsenic(III), antimony(III) and bismuth(III)

Tris-N(ethyl, m-tolyl) dithiocarbamato complexes of arsenic(III), antimony(III) and bismuth(III) abbreviated as As(S₂CNRR′)₃ Sb(S₂CNRR′)₃ and Bi(S₂CNRR′)₃, respectively, where R  C₂H₅ and R′  m-C₆H₄CH₃, have been synthesized. These complexes have been characterized on the basis of elemental analyses, molecular weight determinations, conductance measurements and infrared spectral studies. Thermal studies of these complexes have been carried out in nitrogen and air to determine their modes of decomposition. Kinetic parameters, such as apparent activation energy and order of reaction, have been determined by the graphical method of Coats and Redfern [1].     

Heterogeneous reactions of solid nickel(II) complexes,IV

The decomposition heats (ΔH) for complexes of the type Ni(NCS)₂L₂ were studied by means of a differential scanning calorimeter. From the decreasing values ofΔH the following order has been established:a) for pseudooctahedral complexes: py >β-pic > > Q; andb) for square-planar complexes: 2,6-lut > Q >α-pic. The results obtained are compared with the data from the TG, DTG, and DTA curves.     

Thermal studies on thorium(IV) complexes of 1-butyl-1-methylpiperazinium iodide

Thorium(IV) complexes of the type Th(NO₃)₄·3L·2C₂H₅OH, Th(SCN)₄·L·C₂H₅OH and Th(SO₄)₂·2L·2C₂H₅OH (L=1-butyl-1-methylpiperazinium iodide(I) have been synthesised. From thermogravimetric (TG) curves, the decomposition pattern of the compounds has been analysed. The order, activation energy and apparent activation entropy of the thermal decomposition reaction have been elucidated. The heat of reaction has been calculated from differential thermal analysis (DTA) studies.     

Furopyridines and furopyridine-Ni(II) complexes

Summary The thermal decomposition of the complexes Ni(SCN)₂(fp)₄·2H2O (I), Ni(SCN)₂(mfp)₄ (II) and Ni(SCN)₂(dmfp)₃ (III) (where fp=furo[3,2-c]pyridine, mfp=2-methylfuro[3,2-c]pyridine and dmfp=2,3-dimethylfuro[3,2-c]pyridine) have been investigated in dynamic air from room temperature to 1000°C by means of TG, DTG and DTA. The chemical composition of the complexes, solid intermediates and the resultant products of thermolysis have been identified by means of elemental analysis and complexometric titration. The results revealed that NiO was left as residue at the end of the thermal degradation experiments. IR data suggested that fp, mfp and dmfp were coordinated to Ni(II) through the N atom of the respective heterocyclic ring.     

Thermal decomposition study and biological characterization of zinc(II) 2-chlorobenzoate complexes with bioactive ligands

New zinc(II) 2-chlorobenzoates of general formula [Zn(2-ClC₆H₄COO)₂(L)₂] (where L = caffeine—caf, urea—u, methyl-3-pyridylcarbamate—mpc, phenazone—phen, theophylline—thp) were synthesised and characterised by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied by TG/DTG and DTA methods in nitrogen and in air atmosphere. During the thermal decomposition of the studied compounds the release of organic ligands take place followed by the decomposition of 2-chlorobenzoate anion. The volatile decomposition intermediates were proved by mass spectrometry. Zinc oxide was found as the final product of the thermal decomposition performed up to 1,000 K. The antimicrobial activity of the zinc(II) complexes against various strains of bacteria, yeasts and filamentous fungi has been investigated. It was found that the prepared compounds decreased the growth of Staphylococcus aureus, Escherichia coli, Candida albicans, Rhizopus oryzae and Microsporum gypseum, respectively. The most resistant to all tested compounds was probiotic strain of Lactobacillus plantarum. The presence of zinc and ligands in the prepared compounds increased the inhibitory effect compared to sodium salt of prepared compounds and free ligands.     

Thermal decomposition and biological activity studies of some transition metal complexes derived from mixed ligands sparfloxacin and glycine

The synthetic method of novel ternary M(II)/(III)/(IV) complexes, with fluoroquinolone drug sparfloxacin (HSFX) and glycine (HGly) containing nitrogen and oxygen donor ligand have been synthesized and characterized. The prepared complexes fall into stoichiometric formulae of [M(SFX)(Gly)(H₂O)₂]Cl (M = Cr(III) and Fe(III), [M(SFX)(Gly)(H₂O)₂] (M = Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and UO₂(II) and [Th(SFX)(Gly)(H₂O)₂]Cl₂. The chelate rings are six-membered and six coordinate with 1:1:1 [M]:[SFX]:[Gly]. The important bands in the IR Spectra and main ¹H NMR signals are tentatively assigned and discussed in relation to the predicted molecular structure. The IR data of the HSFX and HGly ligands suggested the existing of a bidentate binding involving carboxylate O and carbonyl O for HSFX ligand and amino N and carboxylate O atoms for HGly ligand. The coordination geometries and electronic structures are determined from the diffused reflectance spectra and magnetic moment measurements. The complexes exist in octahedral form. The complexes decomposed in four to six steps within the temperature range 30–1,000 °C with metal oxides as residues of decomposition. The decomposition steps are accompanied by endothermic or exothermic peaks in the DTA. The HSFX drug, HGly and metal complexes have been screened for their in vitro antibacterial activities against Staphylococcus aureus and Escherichia coli, and antifungal activities against Aspergillus niger and Candida albicans by MIC method. The metal complexes were found to have higher antimicrobial activity than the HSFX drug and HGly ligand and their activity are comparable with the antibacterial and antifungal standards.     

Physical characteristics,vibrational spectroscopy and normal-coordinate analysis of 2-aminophenol and 2-phenylenediamine complexes

Hg(II) and Cd(II) complexes with 2-aminophenol (Amph) and 2-phenylenediamine (Phda) as ligands were prepared and characterized by elemental analysis, electrical conductivity, thermogravimetric analysis (DTA/TG), X-rays, FT-IR and FT-Raman spectra. The complexes formed can be formulated as [M(L)₂·nH₂O]·mH₂O. The electrical conductivity of 0.001 M DMSO solutions revealed the non-electrolytic behavior of the Amph complexes while Phda complexes behave as a 1:2 electrolyte. DTA analysis reveals the presence of two types of water coordinating as aligned and as water of crystallization. ΔE_a of the stepwise decomposition was evaluated. X-ray powder diffraction studies on the ligands and their complexes are described. The fundamental frequencies of these complexes have been assigned on the basis of normal coordinate calculations, carried out using a generalized valence force field (GVFF). The proposed assignments are discussed in relation to the group frequencies in structurally related molecules and in terms of the computed potential-energy distributions among the symmetry coordinates.     

Thermal behaviour of 8-hydroxyquinoline complexes with nickel(II)/copper(II)/zinc(II) hydroxides

Thermal behaviour of M(OH)₂(8-HQ)₂ (M=Ni, Cu and Zn; 8-HQ=8-hydroxyquinoline) has been studied by dynamic TG and DTA methods in nitrogen atmosphere. The percent weights lost in different temperature range was calculated from TG curves. The mode of decomposition has been supported by endotherms observed in DTA curves of the respective compounds.