Coordination compounds of biological interest: Thermal properties of some compounds of saccharin (o-benzoic sulphimide) with nickel(II) and zinc(II)

The thermal properties of nickel(II) and zinc(II) complexes of saccharin (sacc) (o-benzoic sulphimide) have been studied and compared both with those of cobalt(II) and copper(II) previously studied and with those of ternary complexes of nickel(II) and zinc(II) having both saccharin and pyridine as ligands. The thermal behaviour is discussed in terms of the interaction between metal and ligands, interaction studied by IR spectroscopy, and by reflectance spectroscopy.The classical thermal stability scale Co(II) > Ni(II) > Cu(II) > Zn(II) is always obtained.     

Complexes of divalent metal ions with cinchomeronic and dinicotinic acid thermal properties

The thermal properties of the complexes of cinchomeronic and dinicotinic acid with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA).For the thermal stability of the anhydrous compounds a sequence may be observed for the metal ions with cinchomeronic (3,4-H₂PC) and dinicotinic acid (3,5-H₂PC):

The thermal stability of the pyridine carboxylic acid for each metal of the series is: dinicotinic > cinchomeronicThe activation energy values for each thermal reaction were also calculated, using the Coats and Redfern algorism, by the Univac 1108 computer, by a program properly implemented for the statistical analysis of the data to obtain the reaction order and the activation parameters with the relative confidence limits.     

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).     

Ternary complexes of some phenoxyacetic acid herbicides and pyridines with metal ions of biological interest

Ternary complexes of Co(II), Ni(II) and Cu(II) with pyridine (Py) or 2-methyl pyridine (2-MePy) (primary ligand) and some phenoxyacetic acid herbicides, such as phenoxyacetic acid (PAA), 2-chlorophenoxyacetic acid (2-CPA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) (secondary ligands) have been studied in solution using a potentiometricpH-titration technique in order to test a complexation hypothesis of plant growth regulating activities of these herbicides. From stability constant data, the species distribution have been computed and it was found that the percentage of ternary complex (MAL) is about 60% of the totalM ²⁺ present at highpH indicating greater stability of these ternary complexes. TheMA ⁺ species (M ²⁺-Py andM ²⁺-2-MePy) have shown discriminating behaviour towards the next incoming secondary ligand containing O as donor atoms. Since the stabilities of biologically active (2-CPA, 2,4-D and2,4,5-T) and inactive (PAA) phenoxyacetic acid herbicides in binary (ML ₂) and ternary (MAL) metal complexes were found approximately of the same magnitude, chelation may not thus be the probable mode of action of these plant growth regulators.

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Ternäre Komplexe einiger Phenoxyessigsäure-Herbizide mit Pyridin und Metallionen von biologischer Bedeutung

Zusammenfassung Ternäre Komplexe von Co(II), Ni(II) und Cu(II) mit Pyridin (Py) oder 2-Methylpyridin (2-Me Py) als Primärliganden und einigen Herbiziden vom Phenoxyessigsäure-Typ [Phenoxyessigsäure (PAA), 2-Chlor-PAA (2-CPA), 2,4-Dichlor-PAA (2,4-D) und 2,4,5-Trichlor-PAA (2,4,5-T)] als Sekundärliganden wurden im Hinblick auf eine Komplexierungshypothese der pflanzenwuchssteuernden Wirkung dieser Herbizide mittels potentiometrischerpH-Titration untersucht. Aus den Stabilitätskonstanten wurden die Anteile der einzelnen Spezien in Lösung berechnet. Dabei wurden 60% an ternärem Komplex (MAL) — bezogen auf die totaleM ^2–-Menge — bei hohenpH-Werten festgestellt und damit die größere Stabilität dieser Komplexe gezeigt. DieMA ⁺-Spezies (M ²⁺-Py undM ²⁺-MePy) zeigte ein unterschiedliches Verhalten gegenüber dem nächsten chelierenden Liganden mit O als Donor. Da die Stabilitäten der biologisch aktiven (2-CPA, 2,4-D und2,4,5,-T) und inaktiven (PAA) Liganden in binären (ML ₂) und ternären (MAL) Metallkomplexen in der gleichen Größenordnung liegen, scheint die Komplexierung bei der Regulierung des Pflanzenwuchses bei diesen Herbiziden kein entscheidender Faktor zu sein.

     

Coordination numbers of hydrated divalent transition metal ions investigated with IRPD spectroscopy

Hydration of the divalent transition metal ions, Mn, Fe, Co, Ni, Cu, and Zn, with 5-8 water molecules attached was investigated using infrared photodissociation spectroscopy and photodissociation kinetics. At 215 K, spectral intensities in both the bonded-OH and free-OH stretch regions indicate that the average coordination number (CN) of Mn(2+), Fe(2+), Co(2+), and Ni(2+) is ~6, and these CN values are greater than those of Cu(2+) and Zn(2+). Ni has the highest CN, with no evidence for any population of structures with a water molecule in a second solvation shell for the hexa-hydrate at temperatures up to 331 K. Mn(2+), Fe(2+), and Co(2+) have similar CN at low temperature, but spectra of Mn(2+)(H(2)O)(6) indicate a second population of structures with a water molecule in a second solvent shell, i.e., a CN < 6, that increases in abundance at higher temperature (305 K). The propensity for these ions to undergo charge separation reactions at small cluster size roughly correlates with the ordering of the hydrolysis constants of these ions in aqueous solution and is consistent with the ordering of average CN values established from the infrared spectra of these ions.     

The synthesis,spectroscopic and thermal study of oxamic acid compounds of some metal(II) ions

Summary The preparation of oxamic acid complexes of general formula M(H₂NCOCOO)₂·xH₂O (M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; x = 1 for Cu^II, x = 2 for the other metals) is reported. The i.r. and Raman spectra are discussed considering a trans-octahedral structure, formed by five-membered chelate rings with the amide oxygen and one carboxylic oxygen as donor atoms. The apical positions are occupied by water molecules. The thermal degradation process is very similar for the different complexes, first losing H₂O in one or different steps, then the fragments of the organic ligand to give the metal oxide as residue. The thermal degradation of the Cu^II and Zn^II compounds results in the formation of a new polymeric compound by deprotonation of the primary amide function in an endothermic process, the polymer further decomposes to form the metal oxide.     

The thermolysis of some transition metal chelates with 2-(o-hydroxyphenyl)-benzoxazole

The thermal decomposition of the 2-(o-hydroxyphenyl)-benzoxazole chelates of Cd, Cu(II), Co(II), and Ni were studied on the thermobalance. The metal chelates possessed excellent thermal properties. The first weight losses for the chelates appeared in the 165 to 285° temperature range. The minimum metal oxide levels appeared in the 500 to 595° temperature range.     

Solid-state compounds of 2-chlorobenzylidenepyruvate with some bivalent metal ions

Solid-state M-2-Cl-BP, where M stands for Mn, Fe, Co, Ni, Cu, Zn and Pb and 2-Cl-BP is 2-chlorobenzylidenepyruvate, have been synthesized. Thermogravimetry and derivative thermogravimetry (TG/DTG), simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.     

Solid-state compounds of 2-methoxybenzylidenepyruvate with some bivalent metal ions

Solid-state M-2-MeO-BP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-BP is 2-methoxybenzylidenepyruvate have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal stability and thermal decomposition of these compounds. The results led to information about the composition, dehydration, crystallinity and thermal decomposition of the isolated compounds.     

The thermal decomposition of some heteropolytungstates with transition metal ions

The thermal behaviour of some heteropolytungstates of the 2:11 series was studied by means of T.G. and D.T.A. measurements, I.R. spectrometry and X-ray powder analysis (DEBYE -SCHERRER method).     

Equilibrium studies of some divalent metal ions complexes with pyridoxol,pyridoxal and pyridoxamine

The interaction of vitamin B₆ compounds, pyridoxol, pyridoxal and pyridoxamine with metal ions Mn²⁺, Co²⁺, Ni²⁺ and Hg²⁺ are studied. Values for stability constants are evaluated and the reaction stiochiometries are investigated in aqueous 0.50 M KCl at 25°C. It is shown that only pyridoxamine possesses a fairly good affinity to interact with metal ions. A linear relation holds between the stability constants of the first complex and the ionization potential of the divalent metal ions.     

Dielectric studies of molecular complexes ofDDT with some compounds of biological interest

The molecular complexation ofDDT (acceptor) with some compounds of biological interest as donors (e.g. indole, 2-methylindole, 3-methylindole, benzene and naphthalene) have been studied using refractive index,Guggenheim and dielectric titration plot methods. The interaction between these donors with solvents (CCl₄ and C₆H₆) have also been observed by calculating _ind through _ind=_sol–_inert. These data have shown that the molecular interaction between polar solutes and non-polar aromatics is governed by dipole-induced dipole electrostatic attraction. The dipole moment obtained due to charge transfer (_DA) has also been calculated and found that its value increases with the increase in the extent of interaction between donor and acceptor. These data support the charge-transfer complex formation hypothesis for the mode of action ofDDT on molecular level.

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Dielektrizitäts-Untersuchungen an Molekülkomplexen von DDT mit einigen biologisch relevanten Verbindungen

Zusammenfassung Es wurden Molekülkomplexe vonDDT (als Acceptor) mit einigen Verbindungen von biologischem Interesse (als Donoren: Indol, 2-Methyl-indol, 3-Methyl-indol, Benzol und Naphthalin) mittels Brechungsindex,Guggenheim-Methode und dielektrischer Titration untersucht. Dipolmomentberechnungen ergaben, daß die intermolekulare Wechselwirkung von einer Anziehung induzierter Dipol-Dipol bestimmt wird; es wurde auch der charge-transfer-Anteil des Dipolmoments abgeschätzt. Alle diese Daten unterstützen die Annahme der charge-transfer-Komplexierung vonDDT.

     

Coordination architectures and luminescent properties of 5-(pyrimidyl)tetrazolate (Hpmtz) with group 2 metal ions

Four alkaline earth metal-organic frameworks, [Mg(H₂O)₆]?·?(pmtz)₂ (1), [Ca(pmtz) ₂(H₂O)₃]?·?H₂O (2), [Sr(pmtz)₂(H₂O)₄] (3), and [Ba(pmtz)₂(H₂O)₂]?·?4H₂O (4) [pmtz?=?5-(pyrimidyl)tetrazole anion], were synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. The crystal structures reveal that 1–3 are mononuclear while 4 displays a 2-D layer structure by bis(bidentate) bridging pmtz^?. The luminescence properties of 1–4 were investigated in the solid state at room temperature.     

Refractometric studies of molecular complexes ofDDT with some compounds of biological interest

Formation of molecular complexes betweenDDT as acceptor and indole, 2-methylindole, 3-methylindole, benzene and naphthalene as donors have been studied in carbon tetrachloride using refractometric and differential refractometric measurements. Titration techniques through these measurements have indicated11 stoichiometry of these complexes. Equilibrium constants (K ₁) and extent of electronic polarization were calculated. Two types of complexes were observed, one association involving primarily the benzhydryltrichloromethyl grouping ofDDT with a polar complexing agents, and the other interaction of theDDT aromatic -electron system with -electrons of donors in the complexing molecule. These data support the charge-transfer complex formation hypothesis for the mode of action ofDDT on molecular level.

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Refraktometrische Untersuchungen an Molekülkomplexen von DDT mit einigen biologisch relevanten Verbindungen

Zusammenfassung Es wurde die Bildung von Molekülkomplexen zwischenDDT als Acceptor und Indol, 2-Methyl-indol, 3-Methyl-indol, Benzol und Naphthalin als Donor in CCl₄ mittels Refraktometrie und differenzieller Refraktometrie untersucht. Es wurde11-Stöchiometrie der Komplexe festgestellt, Gleichgewichtskonstanten und das Ausmaß der Elektronenpolarisation wurden berechnet. Zwei Typen von Komplexen wurden beobachtet; in einem Fall erfolgt die Assoziation primär über die Benzhydryltrichlormethyl-Gruppierung desDDT, im anderen Fall über -Elektronenwechselwirkungen. Die Daten unterstützen ein chargetransfer-Modell der Komplexbildung vonDDT mit geeigneten Donormolekülen.

     

Synthesis, characterization and properties of some divalent metal(II) complexes: their electrochemical, catalytic, thermal and antimicrobial activity studies

In this study, we synthesized the amine compound 2-(2-aminoethyliminomethyl)phenol (H(3)A) as the starting material, and then we prepared the polydentate Schiff base ligands from the reactions of the amine compound (H(3)A) with phtaldialdehyde (H(2)L), 4-methyl-2,6-di-formlyphenol (H(3)L(1)) and 4-t-butyl-2,6-di-formylphenol (H(3)L(2)) in the ethanol solution. Moreover, the complexes Cd(II), Cu(II), Co(II), Ni(II), Zn(II) and Sn(II) of the ligands H(2)L, H(3)L(1) and H(3)L(2) have been prepared. All compounds have been characterized by the analytical and spectroscopic methods. In addition, the magnetic susceptibility and molar conductance measurements have been made. The catalytic properties of the mono- and binuclear Co(II) and Cu(II) complexes have been studied on the 3,5-di-tert-butylcatechol (3,5-DTBC) and ascorbic acid (aa) as a substrate. The oxidative C-C coupling properties of the Co(II) and Cu(II) complexes have been investigated on the sterically hindered 2,6-di-tert-butylphenol (dtbp). The antimicrobial activity properties of the ligands and their mono- and binuclear complexes have been studied against the bacteria and fungi. The results have been compared to the antibacterial and fungi drugs. The TGA curves show that the decomposition takes place in three steps for all complexes. Electrochemical properties of the complexes Cu(II) and Ni(II) have been investigated for the first time in acetonitrile by cyclic voltammetry.     

Synthesis, characterisation and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with some bivalent metal ions

Solid state M-4-Me-BP compounds, where M stands for bivalent Mn, Fe, Co, Ni, Cu, Zn, Pb and 4-Me-BP is 4-methylbenzylidenepyruvate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterise and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated complexes.     

The kinetics and mechanisms of thermal degradation of some divalent metal salts of mono(hydroxyethyl) phthalate

The thermal decomposition of lead and manganese salts of mono(hydroxyethyl) phthalate was studied by thermogravimetry and differential scanning calorimetry. The kinetic parameters for the various stages of decomposition of these salts were calculated by different methods and mechanisms are proposed to explain the results.     

Interactions of the hormone oxytocin with divalent metal ions

The interaction of the cyclic nonapeptide oxytocin (OT) with a number of alkaline earth and divalent transition metal ions (X(2+)) was examined employing mass spectrometry (MS) and ion mobility spectrometry (IMS) techniques in combination with molecular dynamics (MD) and density functional theory (DFT) calculations. Under acidic conditions it was found that OT exhibits an exceptionally strong affinity for all divalent metal ions resulting in strong [OT + X](2+) peaks in the mass spectrum. Under basic conditions only Cu(2+) and Ni(2+)-OT complexes were detected and these were singly, doubly, triply, or quadruply deprotonated. Collision-induced dissociation of the [OT - 3H + Cu](-) complex yielded exclusively C-terminal Cu(2+)-containing fragments (Cu(2+)fragment(3-)), suggesting that the Cu(2+) ligation site includes deprotonated C-terminal backbone amide nitrogen atoms and the N-terminal amino nitrogen atom in [OT - 3H + Cu](-). MD and DFT calculations indicate a square-planar complex is consistent with these observations and with experimental collision cross sections. MD and DFT calculations also indicate either an octahedral or trigonal-bipyramidal complex between Zn(2+) and OT is lowest in energy with carbonyl oxygens being the primary ligation sites. Both complexes yield cross sections in agreement with experiment. The biological impact of the structural changes induced in OT by divalent metal ion coodination is discussed.