Investigation of pyrimidine- 5- and pyrimidine-2-carboxylic acids

The dissociation constants of pyrimidine-5- and pyrimidine-2-carboxylic acids were determined to ascertain the effect of the character of the substituent and its position in the pyrimidine ring. This effect was compared with the effect of substituents on the dissociation constants of the corresponding benzoic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 561–562, April, 1972.     

Synthesis and characterization of divalent manganese,cobalt, nickel,copper and zinc complexes with nicotinic acid

Coordination compounds of the transition metal(II) acetylacetonates of the formula [M(NA)₂(acac)₂ ]_n (M = Mn, Co, Ni, Cu and Zn; NA = nicotinic acid and acac = acetyl-acetonate anion) have been synthesized and characterized by chemical analysis, magnetic susceptibility, ligand-field spectra, IR and far-IR spectral measurements as well as photoacoustic spectroscopy in the solid state. Tentative stereochemistries for the complexes isolated in the solid state are suggested. The ligand-field parameters 10 Dq, B, β, λ and CFSE are calculated for cobalt and nickel complexes and are in good agreement with the proposed geometries. The metal ions attain six-coordination through the four oxygens of the anion and two donor atoms of the nicotinic acid ligands acting always as monodentate ligands. The formation of the compound results in a considerable shift of v(M-O) to lower frequencies in all the compounds related to parent acetylacetonates.     

Metal-phenoxyalkanoic acid interactions-XVI. Molecular structures of the divalent cobalt,copper, manganese,nickel and zinc complexes with (2-nitrophe

The crystal structures of 2-nitrophenoxyethanoic acid (2-NPAH), catena-[diaquabis(2-nitrophenoxyethanoato)manganese(II)] (1), tetraaquabis(2-ni     

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 and X-ray studies on double sulphates of uranium(IV) with magnesium,nickel, copper and zinc

Double sulphates of uranium(IV) with Mg, Ni, Cu and Zn with the general formula MU(SO₄)₃·8H₂O were prepared from their respective metal sulphates. All the four compounds are isostructural and belong to monoclinic system. The thermal decomposition at 850 °C results in a single phase of triuranates MU₃O₁₀ which on further heating above 980 °C decompose to give the metal oxide and U₃O₈ in case of Ni and Zn compounds and MUO₄ for Mg and Cu compounds. The activation energy for dehydration of these four compounds has been calculated using non-isothermal thermogravimetric data.

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Zusammenfassung Aus den entsprechenden Metallsulfaten wurden sulfatische Doppelsalze von Uran(IV) und Mg, Ni, Cu und Zn mit der allgemeinen Formel MU(SO₄)₃·8H₂O dargestellt. Alle vier Verbindungen besitzen die gleiche Struktur und gehören dem monoklinen System an. Bei der thermischen Zersetzung bei 850 °C entsteht ein MU₃O₁₀ Einphasentriuranat, welches durch weiteres Erhitzen über 980 °C in das entsprechende Metalloxid sowie im Falle der Ni- und Zn-Verbindungen in U₃O₈, bei den Mg- und Cu-Verbindungen in MUO₄ zerfällt. Unter Anwendung nichtisothermer thermogravimetrischer Daten wurde die Aktivierungsenergie für die Dehydratation dieser vier Verbindungen berechnet.

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, , , MU(SO₄)₃ · 8H₂O, . . 850° MU₃O₁₀, 980° U₃O₈ , MUO₄ . .

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The authors thank Dr. D. D. Sood, Head, Fuel Chemistry Division, for constant encouragement.     

Thermal investigation of cobalt, nickel and copper complexes with 8-aminoquinoline

Complexes of Co(II), Ni(II) and Cu(II) with 8-aminoquinoline were prepared and characterized, and their thermal behaviour and decomposition pathways were studied. The thermal stabilities are discussed in terms of ionic radii, crystal field splitting energy and steric hindrance. The effective roles of the counter-ions (Cl^? and NO ₃ ^? ) on the decomposition temperatures and the final products were also clarified. The energies of activation (E _a ) and the orders of some decomposition reactions were determined. Light is shed on the nature of the interaction of the water of crystallization and the polymorphic transformation phenomenon.     

Thermal studies on nickel(II) and copper(II) complexes of monoethanol- and diethanol-dithiocarbamic acids

Thermoanalytical data (TG/DTA) have been obtained for bis-monoethanoldithiocarbamato nickel(II) and bis-diethanoldithiocarbamato nickel(II) and copper(II) complexes. A thermal decomposition mechanism is proposed for bis-monoethanoldithiocarbamato nickel(II).     

Thermal decomposition of 8-hydroxyquinoline complexes with aluminium,cobalt, manganese and nickel

The conditions of thermal decomposition of aluminium(III), cobalt(II), manganese(II) and nickel(II) 8-hydroxyquinoline complexes have been studied by TG-DSC analysis. The thermal decomposition of these complexes has two stages: dehydration and loss of 8-hydroxyquinoline. The final solid product is an oxide.     

Thermal and structural studies of the chloro complexes of cobalt,nickel and copper with 3-phenylpyridine

The chloro complexes of cobalt, nickel and copper with 3-phenylpyridine were prepared in ethanolic solution from which solid compounds were isolated. The cobalt and copper complexes have stoichiometry M₂LCl₄ while the nickel complex has stoichiometry NiLCl₂. The suggested structure for the cobalt and copper complexes is tetrahedral, while for the nickel complex it is octahedral. Thermal analysis studies show that the cobalt and copper complexes form intermediate complexes before their metal oxides are produced. The nickel complex also forms an intermediate complex and then nickel chloride before the nickel oxide is obtained.     

Thermal,spectral and magnetic studies on glycine complexes of cobalt(II), nickel(II) and zinc(II) with hydrazine

Hydrazinium metal glycinates [(N₂H_{5 2}M(NH₂CH₂COO)₄] and bis(hydrazine)metal glycinates, [M(NH₂CH₂COO)₂(N₂H₄)₂], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.     

Synthesis,spectroscopic, and antimicrobial studies of the bivalent cobalt,nickel, and copper complexes of thioacetamide

A series of metal complexes of cobalt(II), nickel(II), and copper(II) having the general composition [M(L)₂X₂] with thioacetamide have been prepared and characterized by elemental chemical analysis, molar conductance, magnetic susceptibility measurements, mass, IR, EPR, and electronic spectral studies. The IR spectral data suggests the involvement of sulfur and amino nitrogen in coordination to central metal ion. On the basis of spectral studies, an octahedral geometry has been assigned for the cobalt(II) and nickel(II) complexes whereas tetragonal geometry for copper(II) complexes. Thioacetamide and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.     

Thermodynamic studies of dynamic metal ligands with copper(II), cobalt(II), zinc(II) and nickel(II)

The self-assembly of unsymmetrical metal ligands from simpler components circumvents complex synthetic approaches. We show herein how a recently developed three-component assembly to create tripicolylamine-like ligands can be extended to the use of azides rather than pyridines. Substituent effects, metal dependence, and reversibility of the assembly are explored. Further, we show that the extent of assembly directly correlates with the differential binding of the templating metals between dipicolylamine-like and tripicolyamine-like ligands.     

Thermal studies of cobalt(II), nickel(II) and copper(II) 3-substituted-4-salicylideneamino-5-mercapto-1,2,4-triazole complexes

Complexes of Co^II, Ni^II and Cu^II with 3-substituted-4-salicylideneamino-5-mercapto-1,2,4-triazole have been prepared and characterized by elemental analysis, electronic, i.r., e.s.r. and t.g. studies. T.g. studies show that the complexes thermally degrade in two steps. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The activation energies of both the thermal degradation steps lie in the 0.24–42.67 kJ mol⁻¹ range. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thermal and spectral studies of 5-(phenylazo)-2-thiohydantoin and 5-(2- hydroxyphenylazo)-2-thiohydantoin complexes of cobalt(II), nickel(II) and copper(II)

Complexes of 5-(phenylazo)-2-thiohydantoin (L¹) and 5-(2-hydroxyphenylazo)-2-thiohydantoin (HL²) with Co(II), Ni(II) and Cu(II) salts have been synthesised and characterized by elemental analysis, conductivity, magnetic susceptibility, UV-Vis, IR, ESR and TG studies. The magnetic and spectral data suggested octahedral geometry for [L¹M(OAc)₂(H₂O)₂]·xH₂O {M=Ni^ll and Cu^ll} and [L¹CuCl₂(H₂O)]·H₂O (dimeric form for the latter), trigonal bipyramidal geometry for [L²Co(OAc)(H₂O)]·2H₂O, square pyramidal geometry for [L²Ni(OAc)(H₂O)]·H₂O and square planar geometry for [L²CuCl]·2H₂O. TG studies confirmed the chemical formulations of these complexes and showed that their thermal degradation takes place in three to five steps, depending on the type of the ligand and the geometry of the complex. The kinetic parameters (n, E^#, A, ΔH^#, ΔS^# and ΔG^#) of the thermal decomposition stages were computed using the Coats-Redfern and other standard equations and are discussed.     

Synthesis,spectroscopic and voltammetric studies of mixed-ligand copper(II) complexes of amino acids

Two Cu^II complexes of the type [Cu(L¹)(L²)] (where L¹ = tryptophanate or phenylalaninate; L² = cysteine thiolate) have been prepared and characterised, and their spectrophotometric and voltammetric behaviour has been investigated. The results obtained by means of FT-IR, e.s.r., u.v.–vis. spectroscopy and by voltammetry revealed the existence of two different [Cu(L¹)(L²)] complexes. A significance decrease in the g _|| value and, concomitantly, an increase in the d–d transition energy was observed when a mixed-ligand complex is present. The observed anisotropic g-values indicate the presence of Cu^II in a tetragonally distorted octahedral geometry. Formation of a mixed-ligand copper complex can be considered as a type of synergism in the presence of cysteine. The redox state Cu^II or Cu^I of copper in the Cu(L²) complex depends on the analysing conditions, i.e., cysteine forms a Cu^II complex under aerobic conditions and a Cu^I complex in anaerobic media. Tryptophan or phenylalanine is bound to Cu^II ions in the Cu(L¹) complexes.     

Paramagnetic shifts in complexes of N-vinylimidazole with manganese,iron, cobalt,nickel, and copper chlorides

The observed paramagnetic shifts and broadenings of the resonance lines in the PMR spectrum of N-vinylimidazole upon the addition of its complexes with manganese, iron, cobalt, nickel, and copper chlorides are compared.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 994–995, July, 1972.We thank Doctor of Chemical Sciences Yu. N. Molin for his assistance in carrying out this investigation.     

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

A novel series of 16-membered binuclear complexes of octaazatetraimine ligand, [M = Mn^II, Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃] have been synthesized by metal template condensation reactions of o-phenylenediamine with N,N′-diacetylhydrazine in 1:1:1 molar ratio in methanol. The proposed stoichiometry and the bonding of the macrocyclic moiety to metal ions along with the overall stereochemistry have been derived from the results of elemental analyses, magnetic susceptibility, conductivity data and the spectral data revealed from FT-IR, , ESI mass, UV–visible studies. An octahedral geometry has been envisaged for Mn^II, Co^II, and Ni^II complexes while a slight distortion in octahedral geometry has been noticed for Cu^II complexes. The low conductivity data of all the complexes suggest their non-ionic nature.     

2-thiouracil-based cobalt(II), nickel(II) and copper(II) complexes

Summary Cobalt(II), nickel(II) and copper(II) complexes of 2-thiouracil and its arylazo derivatives were prepared. The elemental analysis suggest a range of 11, 21 and 13 stoichiometries. Electronic spectra and magnetic susceptibility measurements were used to infer the structures and the i.r. spectra of the ligands and their complexes to identify the type of bonding.     

Thermal decomposition kinetics of vanillidene anthranilic acid complexes of cobalt(II), nickel(II), copper(II) and zinc(II)

The thermal decomposition of cobalt(II), nickel(II), copper(II) and zinc(II) complexes of the Schiff base vanillidene anthranilic acid was studied by TG. The chelates show somewhat similar TG plots when heated in an atmosphere of air. Thermoanalytical data (TG and DTG) of these chelates 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 differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies, it is concluded that the relative thermal stability of vanillidene anthranilic acid chelates can be aligned as Co(II)Ni(II)>Zn(II)>Cu(II).

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Zusammenfassung Die thermische Zersetzung von Cobalt(II)-, Nickel(II)-, Kupfer(II)- und Zink(II)-Komplexen der Schiffschen Base Vanillidenanthranilsäure wurde thermogravimetrisch untersucht. Die Chelate zeigen in einer Luftatmosphäre ähnliche TG-Kurven. Thermoanalytische Daten (TG and DTG) dieser Chelate werden mitgeteilt, interpretiert und mathematisch analysiert. Ebenfalls werden die Reaktionsordnung und die Energie und Entropie der Aktivierung nach der von Freeman-Carroll angewandten differentiellen Methode, nach der auf der Coats-Redfern-Gleichung basierenden integralen Methode und nach der die Horowitz-Metzger Gleichung benutzenden Näherungsmethode bestimmt. Aus den Befunden wird geschlossen, dass die thermische Stabilität von Vanillidenanthranilsäure-Chelaten in der Reihenfolge Co(II)Ni(II)>Zn(II)> >Cu(II) abnimmt.

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, , . - . . , , - , , - . , Ni>Zn>u.

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We thank Dr. C. P. Savariar, Professor of Chemistry, University of Calicut for encouragement. We are also grateful to the University Grants Commission for the award of a Senior Research Fellowship to one of us (J. C).