Thermal Degradation Studies of Complexes of a Derivative of Phenhomazine (Dibenzo[b,f][1:5]diazocine‐6:12‐Dione (PHZD)) by Thermoanalytical Techniques

Some of the bis‐complexes of a derivative of phenhomazine (dibenzo[b,f][1:5]diazocine‐6:12‐dione; PHZD) with Ni(II), Cu(II), Co(II), Cd(II), Zn(II) and Hg(II) of the general formula M(PHZD)₂X₂ [where X = C1, Br and I], were prepared and identified. These complexes have been characterised on the basis of elemental analysis, and spectroscopic, magnetic and conductance data. The thermal mode of decomposition and thermal stability of these complexes was investigated on the basis of the respective thermal curves in a static air atmosphere. The thermoanalytical investigations indicate that these complexes undergo two‐step changes as temperature is raised, except for Cd(II) and Hg(II) complexes, with the formation of metal oxides as end product. The degradation mechanism of the complexes has also been proposed.     

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 analysis of heterocyclic thione donor complexes. Part V. Nickel(II) complexes of imidazolidine-2-thione

The thermal decomposition of the nickel(II) complexes of imidazolidine-2-thione (Imdt), Ni(Imdt)₄X₂ (X = Cl and Br), have been studied in air and in argon by means of TG and DTG, as well as in nitrogen by DTA. Decomposition schemes have been proposed for the complexes in air and inert atmospheres. End-products have been identified for the reactions in air by means of X-ray powder diffraction. Quantitative DTA has been used to derive reaction enthalpies (ΔH_R) from the melting and decomposition endotherms of Imdt and the complexes in nitrogen. The factors which govern the reaction enthalpies of these complexes have been discussed.     

Thermoanalytical investigations of 4-methylpiperazine-1-carbodithioic acid ligand and its iron(III), cobalt(II), copper(II) and zinc(II) complexes

The thermal decomposition studies on 4-methylpiperazine-1-carbodithioic acid ligand (4-MPipzcdtH) and its complexes, viz. [M(4-MPipzcdtH)_n](ClO4)_n (M=Fe(III) when n=3; M=Co(II), Cu(II) when n=2) and [Zn(4-MPipzcdtH)₂]Cl₂ have been carried out using non-isothermal techniques (TG and DTA). Initial decomposition temperatures (IDT), indicate that thermal stability is influenced by the change of central metal ion. Free acid ligand exhibits single stage decomposition with a sharp DTA endotherm. Complexes, [M(4-MPipzcdtH)_n](ClO₄)_n undergo single stage decomposition with detonation and give rise to very sharp exothermic DTA curves while the complex [Zn(4-MPipzcdtH)₂]Cl₂ shows three-stage decomposition patterns. The kinetic and thermodynamic parameters, viz. the energy of activation E, the frequency factor A, entropy of activation S and specific rate constant k, etc. have been evaluated from TG data using Coats and Redfern equation. Based upon the results of the differential thermal analysis study, the [M(4-MPipzcdtH)_n](ClO₄)_n complexes have been found to possess characteristic of high energy materials.     

Thermal and Some other Properties of 2,4′-Bipyridyl Complexes with Various Salts of Lead(II)

New complexes of lead(II) with 2,4′-bipyridyl (L), with the general formulae PbL₂X₂ (where X ^?1=Cl, Br, I, NCS) and PbL₃X₂ (where (X]^?1=NO₃, ClO₄), have been prepared. Analysis of the IR spectra indicates that the 2,4′-bipyridyl is bonded to the Pb(II) ion through the least hindering N(4′). The thermal decompositions of the complexes were studied under non-isothermal conditions in air. The intermediates of decomposition at different temperatures were characterized by thermal analysis (TG and DTG), chemical analysis and X-ray diffraction. Upon heating, the complexes undergo full or partial deamination. The complexes PbL₂Cl₂ and PbL₂Br₂ decompose to volatile lead(II) halide. PbO is the final product of decomposition for the other complexes.     

Preparation, characterization and thermolysis of metal nitrate complexes with 4,4’-bipyridine

Two bis(bipyridine) polymeric metal nitrate complexes with 4,4’-bipyridine of simple formula like [M(bipy)₂](NO₃)2⋅xH₂O (where M=Co, Ni and Cu; x=4, 2 and 0, respectively) have been prepared and characterized. Their thermal decomposition has been undertaken using simultaneous TG-DTG-DTA and DSC in nitrogen atmosphere and non-isothermal TG in air atmosphere. Isothermal TG has been performed at decomposition temperature range of the complexes to evaluate the kinetics of decomposition by applying model-fitting as well as isoconversional method. Possible mechanistic pathways have also been proposed for the thermolysis. Ignition delay measurements have been carried out to investigate the response of these complexes under the condition of rapid heating.     

Metal complexes of omeprazole. Preparation,spectroscopic and thermal characterization and biological activity

Metal complexes of omeprazole (OPZ) are prepared and characterized based on elemental analyses, IR, diffuse reflectance, magnetic moment, molar conductance and thermal analyses (TGA and DTA) techniques. From the elemental analyses, the complexes have the general formula [M(L)₂]X _n [where M = Cr(III) (X = Cl, n = 3), Ni(II) (X = ClO₄, n = 2) and Zn(II) (X = Cl, n = 2)], and [M(L)₂(H₂O)₂]X _n · yH₂O (where M = Fe(III) (X = Cl, n = 3, y = 0), Co(II) (X = Cl or ClO₄, n = 2, y = 0–4) and Ni(II) (X = Cl, n = 2, y = 4) and [Cu(L)₂]Cl₂ · H₂O. The molar conductance data reveal that all the metal chelates are 3 : 1 electrolytes (for Cr(III) and Fe(III) complexes) and 2 : 1 (for the remaining complexes). IR spectra show that OPZ coordinates to the metal ions as neutral bidentate with ON donor sites of the pyridine–N and sulphone-O. The magnetic and solid reflectance spectra indicate octahedral (FeCl₃, CoCl₂, CoClO₄ and NiCl₂), square planar [Cu(II)] and tetrahedral [Mn(II), Cr(III), NiClO₄ and Zn(II)] structures. The thermal behavior of these chelates using thermogravimetric and differential thermal analyses (TGA and DTA) techniques indicate the hydrated complexes lose water of hydration followed immediately by decomposition of the anions and ligand molecules in the successive overlapping OPZ and its metal complexes are screened for antibacterial activity against Escherichia coli, Staphylococcus aureus, Aspergillus flavus and fungi (Candida albicans). The activity data show the metal complexes to be more potent/antibacterial than the parent OPZ ligand against one or more bacterial species.     

Nickel(II) and copper(II) complexes of 2,5-dimethyl-1,3,4-thiadiazole

Summary Nickel(II) and copper(II) complexes of 2,5-dimethyl-1,3,4-thiadiazole Ni(DTZ)X₂ (X = Cl or Br) and M(DTZ)₂X₂ (M = Ni, X = 1 or N03; M = Cu, X = Cl, Br or NO₃) have been prepared. The i.r. spectra show that in all the complexes the ligand is N,N- or N-bonded to the metal while the sulfur atom does not participate in coordination, and that the halide ions are coordinated forming terminal M-X bonds. The NO ₃ ^- group is coordinated in both the nitrato complexes. Magnetic moments of 3.07–3.29 B.M. for the nickel(II) and 1.86–1.92 B.M. for the copper(II) complexes were observed. The Ni(DTZ)X₂ complexes have a pseudo-tetrahedral [N₂X₂] coordination with N,N-bridging ligand molecules. The Ni(DTZ)₂X₂ and Cu(DTZ)₂X₂ complexes, with predominantly monodentate ligand, involve six-coordinate metal atoms with strong equatorial [N₂X₂] bonds and weaker axial bonds.Author to whom all correspondence should be directed.     

Synthesis,spectral and thermal characterization of 6-hydroxymethyl pyridine-2-carboxylic acid methyl ester and its complexes

New pincer ligand, 6-hydroxymethylpyridine-2-carboxylic acid methyl ester, HL, and its bipositive, tripositive and uranyl metal complexes have been synthesized and characterized by elemental and thermal analyses, IR, diffuse reflectance and ¹H NMR spectra, molar conductance and magnetic moment measurements. The downfield shift of the aliphatic OH signal (from 3.87 vs. 2.96 ppm in the ligand) upon complexation indicates the coordination by protonated aliphatic OH group. Zn(II) and UO2(II) complexes are found to be diamagnetic as expected. The low molar conductance values indicate that Ni(II) and Zn(II) complexes are non electrolytes; Fe(II), Co(II), Cu(II) and UO₂(II) complexes are 1:2  electrolytes while Fe(III) complex is a 1:3 electrolyte. The general compositions of the complexes are found to be [M(HL)X₂]·nH₂O where M=Ni(II) (X=Cl, n=1) and Zn(II) (X=Br, n=0); and [M(HL)₂]X_m·nH₂O where M=Fe(II) (X=Cl, m=2, n=0), Fe(III) (X=Cl, m=3, n=4), Co(II) (X=Cl, m=2, n=0), Cu(II) (X=Cl, m=2, n=0) and UO₂(II) (X=NO₃, m=2, n=0). The thermal behaviour of the complexes has been studied and different thermodynamic parameters are calculated using Coats-Redfern method.     

Mixed dimethyl sulfoxide-thiocarbamic ester complexes of platinum(II) halides

Summary The platinum(II) halidecis-[Pt(DMTC)(DMSO)X₂] andcis-[Pt(DETC)(DMSO)X₂](X=Cl or Br; DMSO=dimethyl sulfoxide; DMTC=EtOSCN-Me₂; DETC=EtOSCNEt₂) adducts and the platinum(II) and palladium(II) halide adducts,trans-[M(DETC)₂X₂] (M=Pt or Pd; X=Cl or Br), have been prepared. The complexes were characterized by i.r., and¹H and¹³Cn.m.r. spectroscopy. Both DMTC and DETC coordinate through the sulphur atoms. The 1:2 DETC complexes present the usualtrans configuration, whereas the presence of DMSO favourscis geometry in the mixed species.     

Thermal studies on anisaldehyde carbohydrazone methyl trimethylammonium chloride complexes of zinc,cadmium and mercury

The kinetic parameters of the thermal decomposition of Zn, Cd and Hg(II) hydrazone complexes of the general formula [MCl₂(AGT)₂]Cl₂, where AGT=anisaldehyde carbohydrazone methyl trimethylammonium cation, $$CH_3 O - C_6 H_4 - CH = N - NH - CO - CH_2 - \mathop N\limits^ + (CH_3 )_3 ,$$ and M=Zn, Cd and Hg(II), have been determined from the corresponding thermal curves. The order of the reaction (n) and the activation energy (E _a) have been derived. The kinetic data are discussed in terms of the effect of the metal ion on the activation energy. A thermal decomposition mechanism is suggested.     

Thermoanalytical investigation and biological properties of zinc(II) 4-chloro- and 5-chlorosalicylates with N-donor ligands

New zinc(II) 4- and 5-chlorosalicylate complexes of general formula [Zn(X-sal)₂(L) _n (H₂O) _x ] (where X-sal?=?4-Clsalicylate, 5-Clsalicylate; L?=?N,N-diethylnicotinamide, isonicotinamide, theophylline; n?=?1, 2; x?=?0, 1, 2, 4) were prepared. The complexes were determined by elemental analysis and characterised by infrared spectroscopy. The thermal behaviour of the complexes was studied by simultaneous TG, DTG and DTA methods under dynamic air conditions. The thermal decomposition is a multi-step process. In the first step of the thermal decomposition, water is released in hydrated compounds. The anhydrous compounds start to decompose by the release of organic ligand, followed by chlorosalicylic acid, chlorophenol and carbon monoxide. The final solid product of the thermal decomposition is zinc oxide. The volatile products of the thermal decomposition were determined by mass spectrometry. The antimicrobial activities of the complexes were evaluated against selected pathogen and probiotic bacteria, yeasts and fungi strains. Bioactivities of the tested compounds are different against bacteria, yeasts and filamentous fungi. It was found that bacteria were more sensitive to the studied zinc(II) complex compounds than yeasts or filamentous fungi.     

Co-ordination compounds of diacetyldihydrazone and diacetylbis(monomethylhydrazone)

Summary Diacetyldihydrazone (DADH) forms only six-coordinate complexes with iron(II), cobalt(II), nickel(II) and zinc(II). In M(DADH)₂X₂ (M=Fe, X=Br or I; M=Co, X=I; M=Ni, X=Cl, Br or NCS) the ligand is chelating in the [M(DADH)₃]²⁺ cations, while in M(DADH)₂X₂ (M=Co, X=Cl or Br; M=Ni, X=Cl or Br) the ligand is probably bridging and bidentate. Diacetylbismonomethylhydrazone (DAMH), by contrast, forms predominantly tetrahedral complexes M(DAMH)X₂ (M=Fe or Co, X=Cl or Br; M=Ni, X=Br; M=Co, X=NCS; M=Zn, X=Cl, Br or NCS) and some octahedral complexes M(DAMH)₂X₂ (M=Co, X=NCS; M=Ni, X=Br). The i.r. spectra, electronic spectra and magnetic moments of the complexes are discussed.     

Transition metal complexes of heterocyclic Schiff base

Metal complexes of Schiff base derived from 2-furancarboxaldehyde and 2-aminobenzoic acid (HL) are reported and characterized based on elemental analyses, IR, ¹H NMR, UV-Vis, solid reflectance, magnetic moment, molar conductance and thermal analysis. The ligand dissociation as well as the metal-ligand stability constants have been calculated pH-metrically at 25°C and ionic strength μ=0.1 (1 M NaCl). The complexes are found to have the formulae [M(HL)₂](X)_n·yH₂O (where M=Fe(III) (X=Cl, n=3, y=4), Co(II) (X=Cl, n=y=2), Ni(II) (X=Cl, n=y=2), Cu(II) (X=Cl, n=y=2) and Zn(II) (X=AcO, n=y=2)) and [UO₂(L)₂]·2H₂O. The thermal behaviour of these chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The ligand and its metal complexes show a biological activity against some bacterial species.     

Spectroscopic, thermal and antitumor investigations of sulfasalazine drug in situ complexation with alkaline earth metal ions

The complexes of sulfasalazine (H₃Suz) with some of alkaline metals Mg(II), Ca(II), Sr(II) and Ba(II) have been investigated. Sulfasalazine complexes were synthesized and characterized by spectroscopic tools; infrared spectra, electronic and mass spectra. The IR spectra of the prepared complexes were suggested that the H₃Suz behaves as a bi-dentate ligand through the carboxylic and phenolic groups. The molar conductance measurements gave an idea about the non-electrolytic behavior of the H₃Suz complexes. The thermal decomposition processes for metal(II) complexes of H₃Suz viz: [M(HSuz)(H₂O)₄] (where M = Mg(II), Ca(II), Sr(II) or Ba(II)) have been accomplished on the basis of TG/DTG and DTA studies, and the formula conforms to the stoichiometry of the complexes based on elemental analysis. The kinetic analyses of the thermal decomposition were studied using the Coats–Redfern and Horowitz–Metzger equations. The antitumor and antimicrobial activities of the H₃Suz and their alkaline metal(II) complexes were evaluated.     

Thermal analysis of flammability

The present article describes the synthesis, structural features and thermal studies of the complexes of the type [M(SB)₂(H₂O)₂]·nH₂O [where HSB=pyridine-m-carboxaldene-o-aminobenzoic acid and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)]. The complexes have been characterized on the basis of elemental analyses, magnetic susceptibility measurements, (FTIR and electronic) spectra and thermal studies. The nature of the bonding has been discussed on the basis of infrared spectral data. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated structure of these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature. The thermal decomposition of the complexes have been studied and indicates that not only the crystallization and coordinated water are lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass losses. The kinetic parameters such as order of reaction (n) and the energy of activation (E _a) have been reported using Freeman–Carroll method. The entropy (S*), the pre-exponential factor (A), the enthalpy (H*) and the Gibbs free energy (G*) have been calculated.     

Thermal properties of cyanatocopper(II) complexes with pyridine,bipyridine and phenanthroline

The thermal properties of cyanatocopper complexes with pyridine, bipyridine and phenanthroline are described in this paper. It was found that the thermal stabilities of the complexes were found to increase in the order pybipy2(NCS)₂ (L=pyridine and its methyl derivates) which are composed of the liberation of ligandsL and redox reactions of thiocyanate ligands with the central Cu(II) atom [1, 2]. The decomposition temperature of thiocyanate ligands depends on the properties of the ligandsL present in the coordination sphere. An analogous course of thermal decomposition was also observed for [Cu(bipy)₂(NCX)](NCX) (X=S or Se) [3]. For the phenanthroline complexes [Cu(phen)₂(NCX)₂] (X=S or Se) the thermal stability was found to increase significantly (by about 140C) and the decomposition stoichiometry was also changed [3].The present paper contains the results of thermoanalytical studies on bipyridine and phenanthroline cyanatocopper complexes, and a comparison of the thermal properties of pyridine cyanato and isothiocyanatocopper complexes.     

Thermoanalytical investigations of tris(ethylenediamine)nickel(II) oxalate and sulphate complexes

Investigations on the thermal behaviour of [Ni(en)₃]C₂O₄·2H₂O and [Ni(en)₃]SO₄ have been carried out in air and helium atmosphere. Simultaneous TG/DTA coupled online with mass spectroscopy (MS) in helium atmosphere detected the presence of H₂, O, CO, N₂/CH₂=CH₂ and CO₂ fragments during the decomposition of tris(ethylenediamine)nickel(II) oxalate and H₂, O, NH, NH₂, NH₃ and N₂/CH₂=CH₂ fragments for tris(ethylenediamine)nickel(II) sulphate complex. The thermal events during the decomposition were monitored by temperature-resolved X-ray diffraction. In air, both the complexes give nickel oxide as the final product of the decomposition. In helium atmosphere, tris(ethylenediamine)nickel(II) oxalate gives nickel as the residue, whereas tris(ethylenediamine)nickel(II) sulphate gives a mixture of nickel and nickel sulphide phases as the final residue. Kinetic analyses of these complexes by isoconversional methods are discussed and compared.     

Metal ion complexes of 2-picolinamineN-oxide

Summary A series of cobalt(II), nickel(II) and copper(II) complexes of 2-picolinamineN-oxide, HA, has been prepared. Solids of formula [M(HA)₃](BF₄)₂ (M=cobalt(II) or nickel(II); [Cu(HA)₂]X₂ (X=BF ₄ ^– , NO ₃ ^– ); [Co(HA)₂X₂] (X=Cl^– or Br^–); [Ni(HA)₂Cl₂] and [Cu(HA)X₂] (X=Cl^– or Br^–] have been isolated and characterized by partial elemental analyses, molar conductivities, magnetic susceptibilities, DSC-TGA, and spectral methods. All complexes were found to be monomeric, and their spectral parameters are compared with those of the metal ion complexes ofN-alkyl-2-picolinamineN-oxides, 2-dialkylaminopyridineN-oxides and 2-picolinamine. The cobalt(II) and nickel(II) halide complexes spectrally show a mixture of octahedral and tetrahedral centres.     

The infrared spectra (600-150 cm−1 of pyridine N-oxide complexes of metal(II) halides and mixed-ligand (pyridine N-oxide—dimethylsulphoxide) complexes of copper(II) halides

The infrared spectra of the complexes [M(pyO)(H₂O)Cl₂] (M = Mn, Fe, Co, Ni, Cu; pyO = pyridine N-oxide) have been determined. Assignments of ν M-Opy, νM-OH₂ and ν M-Cl are made by observing the effects of deuterating the coordinated pyO and H₂O and replacing chloride by bromide in the Mn(II) complex. Assignments of metal—ligand modes in the mixed ligand complexes [M(pyO)(dmso)X₂] (dmso = dimethylsulphoxide) are made by comparison with the spectra of (ML₂X₂] (L = pyO, dmso) and by observing the effects of deuteration of pyO and dmso. Structural aspects of the spectra are discussed.