Thermal studies of some purine compounds and their metal complexes

The mechanism of the decomposition of the entitled compounds and their complexes is studied. Adenine, its Schiff base of salicylaldehyde, and its azo resorcinol derivatives are ended with carbon. However, oxalonitrile compound is appeared as a final product for adenine acetylacetone and an intermediate for adenine. The thermodynamic parameters of the decomposition reaction were evaluated and discussed. The change of entropy values, ΔS ^#, showed that the transition states are more ordered than the reacting complexes. The thermal processes proceed in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H₂O, NH₃, or HCl. In most cases, the free radical species of the ligands are assigned to exist through decomposition mechanisms. The copper adenine and nickel salicylaldehyde complexes are ended with the metal as a final product. However, the cobalt adenine, its acetylacetone, its salicylaldehyde, cadmium and mercury guanine complexes are ended with metal oxides.     

Thermal degradation studies on some metal hydrazinic complexes

The paper deals with the characterization of three hydrazinic complexes with Ni, Cu and Cr respectively, by means of non-isothermal thermal methods, TG, DTG and DTA, under nitrogen atmosphere in order to investigate the structure-thermostability-thermal degradation mechanism correlation. The thermal analysis made evident the degradation mechanisms characteristic of every sample in accordance with the chemical structure. The quantitative analysis by TG-DTG afforded the estimation of the metal amount in the complex on the basis of the resulting metallic oxide nature as well as of some aspects of the thermal degradation mechanism supported by mass spectral measurements. The melting points given by DTA and confirmed by the Boetius method and the initial temperatures of thermal degradation from TG-DTG-DTA afforded to ascertain the temperature range proper for using and storing the complexes under study which show potential practical applications as drugs.     

Thermal properties of some complexes of quinolinic acid with divalent metal ions

Studies of the complexes of pyridinecarboxylic acids with divalent metal ions as a function of the position of the carboxyl groups were extended. The thermal properties of the complexes of quinoline acid (pyridine-2,3-dicarboxylic acid) with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA). A correlation between these compounds and others obtained by reaction between the studied metal ions with similar acids (lutidinic acid (pyridine-2,4-dicarboxylic acid) and isocinchomeronic acid (pyridine-2,5-di-carboxylic acid) is discussed in terms of the position of the carboxyl group far from the aza group. The thermal stability of the metal complexes is in the order Mn(II) > Fe(II) > Zn(II) ? Co(II) > Ni(II) > Cu(II).     

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.     

pH-metric studies on ternary metal complexes of some amino acids and benzimidazole

The stability constants of binary and ternary complexes of copper(II) and nickel(II) with some amino acids (d-histidine, dl-serine, lysine) as primary ligands and benzimidazole as a secondary ligand were determined pH-metrically. The study was conducted in 10% (v/v) ethanol-H(2)O medium and at an ionic strength of 0.1 mol dm(-3) NaNO(3) at 20 +/- 1 degrees C, Values of Delta log K were discussed on the basis of statistical considerations and the nature of the species formed. The stability of the binary and mixed ligand complexes are discussed in terms of the molecular structure of benzimidazole and the amino acids as well as the nature of the metal ion.     

Thermal studies on purine complexes: XII. Thermal behaviour of some metal complexes of hypoxanthine

Some complexes of hypoxanthine with Cu(II), Ag(I), Cd(II), Hg(II), Pd(II), Rh(III) and Pt(IV) have been prepared in ethanolic, aqueous, basic or acid media and characterized on the basis of elemental analysis and IR studies. The thermal behaviour of these compounds has been studied using TG, DTG and DSC techniques. Heats of dehydration, dehalogenation and fusion have been calculated from DSC curves.     

Thermal studies of some divalent metal chelates of croconic acid

The thermal properties of chelates of croconic acid and squaric acid with divalent copper, cobalt, nickel and zinc have been investigated by TG and DTA. The decreasing order of thermal stability for the decomposition of the croconate chelates was Ni > > Zn > Co=Cu and for the squarate complexes, Zn > Co=Cu > Ni. The copper croconate TG showed water loss in two distinct steps. This was rationalized on the basis of the already known Jahn-Teller effect for this molecule. The nickel squarate was thought to have a different structure than the other squarate chelates. Activation energies were calculated for the croconate chelates from their DTA curves.

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Zusammenfassung Die thermischen Eigenschaften der Chelate der Crocon- und Squarsäure mit zweiwertigem Kupfer, Cobalt, Nickel und Zink wurden durch TG und DTA untersucht. Die Abnahme der thermischen Stabilität bei der Zersetzung der Croconat-Chelate verlief von Ni>Zn>Co=Cu und der Squarat-Komplexe von Zn>Co=Cu>Ni. Die TG der Kupfercroconate wies eine Wasserabgabe in zwei deutlichen Stufen auf. Diese erklärt sich aufgrund des bereits bekannten Jahn-Teller Effekts für dieses Molekül. Für Nickelsquarat wurde eine andere Struktur angenommen als für die anderen Squaratkomplexe. Die Aktivierungsenergien für die Croconatchelate wurden aus ihren DTA-Kurven berechnet.

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Résumé Les propriétés thermiques des chélates formés par les acides croconique et squarique avec le cuivre, le cobalt, le nickel et le zinc ont été étudiées par TG et ATD. La stabilité thermique des chélates de l'acide croconique décroît dans l'ordre Ni>Zn>Co=Cu et pour l'acide squarique Zn>Co=Cu>Ni. L'étude TG du croconate de cuivre révèle une perte d'eau en deux étapes distinctes. Ceci s'explique par l'effet Jahn-Teller, déjà connu pour cette molécule. Le squarate de nickel possède sans dute une structure différente de celle des autres chélates de l'acide squarique. Les énergies d'activation des chélates de l'acide croconiqus ont été calculées à partir des courbes ATD.

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TGA DTA , , . Ni > > Zn > =u, — Zn > =Cu > Ni. TGA , . — . , , . DTA .

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Taken in part from a thesis submitted by D. A. L. to the Graduate School of the University of Notre Dame in partial fulfillment for the requirements of the Ph. D. degree.     

Thermal studies of some mixed complexes of Mn(II) with picrate and nitrogen donors

The thermal decompositions of nine mixed ligand complexes of Mn(II) containing picrate and mono- or bidentate nitrogen ligands were studied by thermogravimetry. The kinetics of decomposition were examined by using the Coats-Redfern and Horowitz-Metzger equations; the decomposition was in all cases of the first order. The activation energies and other kinetic parameters were computed. The decomposition mechanisms exhibited a similar character for all the studied compounds. It was observed from the TG curves that the complexes decomposed to give six-coordinate intermediates, formed from substitution of the picrate into the inner coordination sphere. These intermediates decomposed to Mn(II) picrate and finally to Mn₂O₃.     

Synthesis,physico-chemical studies and biological evaluation of new metal complexes with some pyrazolone derivatives

A series of N-substituted-4-thiocarbamoyl-5-pyrazolone derivatives (HL¹-HL⁴) is presented as chelating agents for complexation with Fe(III), Ni(II) and Cu(II) metal ions. The synthesized pyrazolone ligands and their newly metal complexes are characterized by different spectral and analytical methods such as UV–Vis, IR, ¹H NMR, ¹³C NMR, ESR, MS, magnetic measurement, and TGA. The spectral data reveal that ligands coordinated to metal ions in a bidentate pattern via O & N atoms of the OH group at C(5) and thiocarbamoyl (–CSNHR) at C(4) of the pyrazolone ring. Also, the analytical data suggest the stoichiometries 2:3 (M:L) for both Cu(II) & Ni(II) complexes and 1:3 for Fe(III) complexes. Besides, the normal magnetic moments values for Fe(III) complexes confirm high spin octahedral structure while the diamagnetic nature of all Ni(II) complexes is consistent with square planar geometry. However, the subnormal magnetic values for Cu(II) complexes suggest the proposal of their binuclear structures. The ESR spectra of the Cu(II) complexes support the distorted square planar geometry with a considerably strong intradimeric spin-exchange interaction. Moreover, the anticancer, antibacterial and antifungal activities are screened. Among the synthesized compounds, HL⁴ ligand exhibits a significant broad spectrum of action against Gram-positive (S. aureus), Gram-negative bacteria (P. vulgaris), and antifungal potency against A. fumigatus & C. albicans in comparison with gentamicin and ketoconazole drug. Such potency of HL⁴ could be related to the insertion of the p-chloro in the phenyl group attached to the pharmacophoric thiocarbamoyl group at C(4). Furthermore, IC₅₀ values of two Cu(II) complexes derived from HL² and HL³ display nearly twofold or threefold more cytotoxicity impact against three cell lines (MCF-7, HCT116 and HepG-2) compared with cis-platin as positive control.     

Synthesis and characterization of some pyrimidine, purine, amino acid and mixed ligand complexes

Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of barbital, thiouracil, adenine, amino acids (methionine, lysine and alanine) and some mixed ligands were prepared and characterized by elemental analyses, IR, electronic spectra, magnetic susceptibility and ESR spectra. Coordination of the metallic centre to the oxygen and nitrogen atoms of barbital, thiouracil, amino acids and coordinate to amino group and nitrogen atom of adenine occurred. Electronic spectra and magnetic susceptibility measurements were utilized to infer the structure of the complexes which are octahedral for Mn(II), Fe(III), Co(II), Ni(II) and Cd(II) and tetrahedral for Mn(II), Cu(II), Zn(II) complexes. ESR spectra were observed for copper complexes with a d(x2)-(y2) ground state with small g(||) values indicating strong interaction between the ligands and their metal ions.     

Synthesis and spectral characterization of some new azo dyes and their metal complexes

A series of azo-metal chelate dyes have been synthesized by coupling substituted o-nitroaniline and p-t-/s-butylphenol. The spectral characterization of the azo dyes containing o-hydroxy group and azo-metal(II) chelate [metal(II): Cu, Ni, Co] dyes by IR spectra, UV–VIS spectra, NMR spectra, elemental analysis and magnetic susceptibility techniques are reported. The stoichiometry of the azo-metal chelates was determined by the spectroscopic titration method to be 1:2 (ML₂).     

The synthesis and characterization of some new vic-dioximes and their transition metal complexes

In this study, three new vic-dioximes, [L¹H₂], N-(5-chloro-2-methoxyphenyl)amino-1-acetyl-1-yclohexenylglyoxime, [L²H₂],N-(3-chloro-4-methoxyphenyl)amino-1-acetyl-1-cyclohexenylgly-oxime and [L³H₂], N-(3-chloro-2-methoxyphenyl)amino-1-acetyl-1-cyclohexenylglyoxime were synthesized from 1-acetyl-1-cyclohexeneglyoxime and the corresponding substituted aromatic amines. Metal complexes of these ligands were also synthesized with Ni(II), Cu(II) and Co(II) salts. The structures of these new compounds (ligands and complexes) were characterized with FT-IR, magnetic susceptibility measurement, molar conductivity measurements, mass spectrophotometer measurements, thermal methods (TGA), ¹H NMR and ¹³C NMR spectral data and elemental analyses.     

The thermal properties of some metal complexes of diethyldithiocarbamic acid new volatile metal chelates

The cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and mercury(II) complexes of diethyldithiocarbamic acid were prepared and their thermal properties determined by TG, DTA, and high temperature reflectance spectroscopy. It was found that the copper(II), nickel(II), and zinc(II) chelates were completely volatile and thus represent a new class of volatile metal chelates. Vapor pressure measurements were made on four of the metal complexes; heats of vaporization ranged from 9.3±0.2 kcal/mole for Na[Co(DDC)₃] to 24.2±0.6 kcal/mole for Zn(DDC)₂.

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Zusammenfassung Es wurden die Komplexe von Kobalt(II), Nickel(II), Kupfer(II), Zink(II), Cadmium(II), Silber(I) und Quecksilber(II) mit Diäthyldithiokarbaminsäure hergestellt und ihre thermischen Eigenschaften durch Thermogravimetrie, Differentialthermoanalyse und Hochtemperatur Reflexions Spektroskopie untersucht. Man fand, daß die Kupfer(II)-, Nickel(II)- und Zink(II)-Komplexe vollständig verflüchtigen. Sie stellen eine neue Sorte flüchtiger Metallchelate dar. Dampfdruckmessungen wurden an vier der Komplexe unternommen. Die Verdampfungswärmen liegen zwischen den Werten von 9.3±0.2 Kcal/Mol für Na[Co(DDC)₃] bis 24.2±0.6 Kcal/Mol für Zn(DDC)₂.

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Résumé On a préparé les complexes de cobalt(II), nickel(II), cuivre(II), zinc(II), cadrnium(II), argent(I) et mercure(II) avec l'acide diéthyle-dithiocarbaminique et étudié leurs propriétés thermiques par TG, ATD et spectroscopie de reflexion à haute température. On a trouvé que les complexes de cuivre(II), nickel(II) et zinc(II) volatilisent parfaitement; ils représentent une nouvelle sorte de chélates métalliques volatiles. On a fait des mesures de pression de vapeur sur quatre de ces complexes. Les valeurs des chaleurs de vaporisation s'étalent de 9.3±0.2 kcal/mole pour Na[Co(DDC)₃] jusqu'à 24.2±0.6 kcal/mole pour Zn(DDC)₂.

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[II], [II], [II], [II], [II], [I] [II] , . , [II], [II] — . ë -; 9,3±0,2 / Na[Co(DDC)₃] 24,2±0,6 / Zn[DDC]₂.

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The partial support of this work by the U. S. Air Force, Air Force Office of Scientific Research, through Grant No. AF-AFOSR 69-1620, is gratefully acknowledged. One of us (G. D'A.) wishes to thank the National Research Council of Italy, Rome, Italy, for financial support.     

Preparation,structural characterization and biological studies of some new levofloxacin metal complexes

A new series of metal complexes of Ti(IV), V(IV), Y(III), Zr(IV), Ce(IV) and U(VI) with levofloxacin (Levo) were synthesized and characterized by elemental analysis, molar conductivity, magnetic moment measurements, UV–Vis, FT-IR and ¹H NMR, XRD as well as TG-DTG techniques. The data indicated that levofloxacin reacts as a bidentate ligand chelate to the metal ion through the pyridone oxygen and one carboxylato oxygen. The thermal dehydration and decomposition of the complexes were studied kinetically using Coats–Redfern and Horowitz–Metzger methods, and the thermodynamic data reflected the thermal stability for all complexes. The calculated bond length and the bond stretching force constant, F(U=O), values for UO₂ bond are 1.86 Å and 690.67 N m^?1. The biological activities of the levofloxacin, meta-salts and their metal complexes were assayed against different bacterial and fungal species as well as their effect on degradation of calf thymus DNA.     

Syntheses and studies on some metal beta-thioketoester complexes

The syntheses of four metal complexes from ethyl thiobenzoylacetate are described. These complexes are of the type M[C₆H₅C(S)CHC(O)OC₂H₅]_n where M is nickel, palladium, zinc or cobalt and n is 2 or 3. The IR spectra of these complexes show the presence of a chelating conjugated ester carbonyl group. The ¹³C NMR spectra and dipole moment data of these complexes are also presented and a comparison of the dipole moments of these metal complexes of C₆H₅CSCH₂COR′ where R′ is OC₂H₅ or CF₃ is made. The ¹³C NMR spectrum of the octahedral cobalt complex suggest a facial configuration.     

Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH₂-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D ₀) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H⁺, e⁻, e⁻, H⁺. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) were determined potentiometrically at room temperature.      

Thermal stability of some azo-derivatives and their complexes

this paper deals with the first investigation concerning the thermal stability of two 1-(2-benzothiazolyl)-3-methyl-4-azo-pyrazil-5-one derivatives and their Cu(II) coordination compounds of type ((C₄H₉)₄N)₂[Cu(L)₂]. The thermal decomposition steps were established. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectral, thermal and X-ray studies on some new bis-hydrazine metal glyoxylates and bis-hydrazine mixed metal glyoxylates

Bis-hydrazine complexes of metal glyoxylates and mixed metal glyoxylates of 3d-metal ions of the formula M(OOCCHO)₂(N₂H₄)₂, where M = Mg, Mn, Co, Ni, Cu, Zn or Cd and M_1/3Co_2/3(OOCCHO)₂(N₂H₄)₂, where M = Mg, Mn, Ni, Zn or Cd, respectively, have been prepared and studied. The compositions of the complexes have been determined by chemical analyses. The magnetic moments and electronic spectra suggest a high-spin octahedral geometry for the metal complexes. Infrared spectral data indicate the bidentate bridging by hydrazine molecules and monodentate coordination by glyoxylate ions in both the metal and mixed metal compounds. Thermogravimetry and differential thermal analyses in air have been used to study the thermal behaviour of the complexes. The simultaneous TG-DTA traces of all the complexes show multi-step degradation and the final products are found to be the respective metal oxides in the case of metal complexes and metal cobaltites in the case of mixed metal complexes. The final residues were identified by their X-ray powder diffraction patterns. X-ray powder diffraction patterns of the complexes including mixed metal complexes are almost superimposable with in each of the series indicating isomorphism. The metal cobaltites MCo₂O₄, where M = Mg, Mn, Ni, Zn or Cd were also prepared by decomposing the respective mixed metal complex in a pre-heated silica crucible at about 300 °C, and their identities were confirmed by chemical analyses, infrared spectra and X-ray powder diffraction.     

Thermal study of new biologic active complexes with mixed ligands

Five new coordinative compounds that contain mixed ligands (4,4′-bipyridine and methacrylate anion) were synthesized and characterized (elemental analysis, IR and UV–Vis spectroscopy, and thermal studies). The complexes are of the type [M(4,4′-bipy)(C₄H₅O₂)₂]·nH₂O ((1) M:Mn, n = 0; (2) Co, n = 0.5; (3) M:Ni, n = 1.5; (4) M:Cu, n = 0.5; (5) M:Zn, n = 0.5; 4,4′-bipy: 4,4′-bipyridine; C₄H₅O₂: methacrylate anion). All the tested complexes exhibited very low MIC values against Escherichia coli strains and one compound against Staphylococcus aureus. Besides the specific antimicrobial spectrum, these compounds also inhibited the microbial ability to colonize the inert surfaces, acting as potential anti-adherence and biofilm-controlling agents. The thermal behavior provided confirmation of the complexes' compositions as well as the number and the nature of water molecules and the intervals of thermal stability.     

Synthesis and structural studies of new Mannich base ligands and their metal complexes

The new Mannich bases bis(1,4-diphenylthiosemicarbazide methyl) phosphinic acid H₃L¹ and bis(1,4-diphenylsemicarbazide methyl) phosphinic acid H₃L² were synthesised from the condensation of phosphinic acid, formaldehyde with 1,4-diphenyl thiosemicarbazide and 1,4-diphenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formulae K₂[Cr^III(L ⁿ )Cl₂], K₃[Mn^II(L ⁿ )Cl₂] and K[M(L ⁿ )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Hg(II); n = 1, 2), are reported. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed octahedral geometries for the Cr(III), Mn(II) complexes, square planar for Co(II), Ni(II) and Cu(II) complexes and tetrahedral for the Zn(II) and Hg(II) complexes.