Characterization studies of some bi- and tetradentate bifunctionalSchiff base complexes with Co(II), Ni(II), and Cu(II)

Co(II), Ni(II) and Cu(II) complexes of some bifunctional arylidene-o-phenylenediamineSchiff bases have been prepared. Formation, stoichiometry and stability of the complexes have been tested in solution using electronic spectral measurements. Characterization of the complexes has been accomplished primarily by elemental analysis, molar conductance as well as electronic and IR spectral measurements. It is concluded that theo,o-hydroxy derivative (L ₁) acts as a bivalent ONNO tetradentate ligand while the molecules of the other derivatives (L ₂-L ₅) are coordinated to the metal ions as bidentate NN ligands. The Cu(II)-L ₁ complex is suggested to possess a tetrahedral geometry whereas the other complexes are suggested to exhibit a distarted octahedral geometry. The different bands observed in the electronic spectra of the complexes inDMF solutions have been assigned to the -*,L M CT and d-d electronic transitions.

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Untersuchungen zur Charakterisierung einiger zwei- und vierzähniger bifunktionellerSchiffbasen-Komplexe mit Co(II), Ni(II) und Cu(II)

Zusammenfassung Es wurden die Co(II)-, Ni(II)- und Cu(II)-Komplexe einiger bifunktioneller Aryliden-o-phenylendiamin-Schiffbasen hergestellt. Unter Verwendung elektronenspektroskopischer Methoden wurde die Bildung, Stöchiometrie und Stabilität der Komplexe in Lösung untersucht. Die Charakterisierung erfolgte mittels Elementaranalysen, Leitfähigkeitsmessungen und Elektronen- bzw. IR-Spektroskopie. Es wird darauf geschlossen, daß daso,o-HydroxyderivatL ₁ als bivalenter vierzähniger ONNO Ligand wirkt, während die anderen Derivate (L ₂-L ₅) als zweizähnige NN Liganden an die Metallionen koordiniert sind. Für den Cu(II)-L ₁ Komplex wird eine tetraedrische Geometrie vorgeschlagen, währenddessen die anderen Komplexe eine verzerrte octaedrische Geometrie aufweisen. Die in den Elektronenspektren der Komplexe inDMF-Lösung auftretenden Banden werden den -*,L M CT und d-d Elektronenübergängen zugeordnet.

     

Synthesis and properties of iron(II) and iron(III) complexes with 3-(α,γ-dicarboxy-n-propylidene-hydrazino)-5,6-diphenyl-1,2,4-triazine (DCPT)

Summary Proton-ligand formation constants ofDCPT and metal-ligand formation constants of its complexes with Fe(II) and Fe(III) have been determined potentiometrically at 10, 20, 30, and 40°C in 75% (v/v) dioxane-water at 0.10M ionic strength (KNO₃). The thermodynamic parameters G, H, and S have also been evaluated. The possibility of formingM(HL),M(HL)₂, andM(HL)₃ species was substantiated from potentiometric and electronic absorption measurements. The values of the stability constants logK _M(HL), log , and log derived from the spectrophotometric method are in good agreement with those obtained from potentiometric data. The use ofDCPT as an analytical reagent for the spectrophotometric determination of iron is discussed. The solid complexes have been characterized by chemical analysis and magnetic susceptibility, IR, NMR, and electronic spectral data.

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Synthese und Eigenschaften von Eisen(II)- und Eisen(III)-Komplexen mit 3-(,-Dicarboxy-n-propylidene-hydrazino)-5,6-diphenyl-1,2,4-triazin (DCPT)

Zusammenfassung Die Bildungskonstanten sowohl vonDCPT als auch seiner Komplexe mit Fe(II) und Fe(III) wurden bei 10, 20, 30 und 40°C in Dioxan-Wasser (75% (v/v)) bei einer lonenstärke von 0.1M KNO₃ potentiometrisch bestimmt. Zusätzlich wurden die thermodynamischen Parameter G, H und S ermittelt. Die Wahrscheinlichkeit des Auftretens von Komplexen der ArtM(HL),M(HL)₂ undM(HL)₃ wurde mittels potentiometrischer und absorptionsspektroskopischer Messungen erhärtet. Nach beiden Methoden ermittelte Stabilitätkonstanten stimmen gut überein. Die Verwendung vonDCPT als analytisches Reagens zur spektrophotometrischen Eisenbestimmung wird diskutiert. Die Komplexe konnten in Substanz hergestellt werden und wurden durch chemische Analyse und über ihre magnetischen und spektroskopischen Eigenschaften charakterisiert.

     

Use of arsenite reduction in potentiometric methods for arsenic(III) or higher valent lead,manganese, chromium,and vanadium in some industrial products

A simple, rapid, and reliable method is given for determination of As(III) based on arsenite reduction of alcoholic iodine and titration of the equivalent iodide with Hg(II) using silver amalgam as the indicator electrode. Arsenite reduction is applied to the estimation of lead in minium, manganese in duralumin, chromium in zinc chromate, and vanadium and chromium in ilmenite, the excess of arsenite being determined by the same method used for As(III). The endpoints are accurately determined with very satisfactory potential breaks.     

Synthesis, Spectral Characterization and Electrochemical Properties of New vic-dioxime Complexes Bearing Carboxylate

Three new vic-dioxime ligands, [N-(ethyl-4-amino-1-piperidine carboxylate)-phenylglyoxime (L¹H₂), N-(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L²H₂), and N,N′-bis(ethyl-4-amino-1-piperidine carboxylate)-glyoxime (L³H₂)], and their Co(II) with Cu(II) metal complexes, were synthesized for the first time. Mononuclear complexes of these ligands with a 1:2 metal-ligand ratio were prepared with Co(II) and Cu(II) salts. The BF₂⁺-capped Co(II) and mononuclear complexes of the vic-dioxime were prepared for [Co(L¹·BF₂)₂] and [Co(L²·BF₂)₂]. The ligands act in a polydentate fashion bonding through nitrogen atoms in the presence of a base, as do most vic-dioximes. The cobalt(II) and copper(II) complexes are non-electrolytes as shown by their molar conductivities (Λ_M) in DMF. The structures of the ligands and complexes were determined by elemental analyses, FT-i.r., u.v.–vis., ¹H- and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, and molar conductivity. The comparative electrochemical studies show that the stabilities of the reduced or oxidized species and the electrode potentials of the complexes are affected by the substituents attached on the oxime moieties of the complexes.     

Synthesis and GIAO NMR calculations for some new 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives: comparison of theoretical and experimental 1H and 13C chemical shifts

Four novel 3-alkyl(aryl)-4-(4-methoxycarbonylbenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1) with methyl 4-formylbenzoate and characterized by elemental analyses and IR, 1H NMR, 13C NMR and UV spectral data. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound was optimized using the 6-311G basis set.     

Determination of cis and trans isomers of monocrotophos in technical products by reversed-phase column liquid chromatography

A simple reversed-phase column liquid chromatographic method for the determination of cis and trans isomers of monocrotophos (MCP) using a C18 column, aqueous acetonitrile as eluent and UV detection at 218 nm was developed. The method was used for quality assurance and to study the relative stabilities of cis and trans isomers in technical products of MCP.     

Pictet‐spengler synthesis of pyrazole‐fused β‐carbolines

The synthesis of new pyrazolo[4,3‐c]β‐carbolines ( 8a,b ) is achieved by condensation of the appropriate aldehyde with 3‐(4‐amino‐1,3‐dimethylpyrazol‐5‐yl)indole ( 4 ) under Pictet‐Spengler reaction conditions. Regioselective cyclization occurred at the usual indole C‐2 position as evidenced from the ¹H‐and ¹³C nmr spectra of 8a,b which lack the pyrrolic H‐2 signal, present in 4 (δ 7.26, 1H, d, J_ch‐NH = 2‐5 Hz).     

Voltammetric studies on some substituted 5-arylidene-2-thiohydantoin in non aqueous medium

Summary Differently substituted 5-arylidene-2-thiohydantoins (2a–f) were studied electrochemically in benzonitrile with 0.1M tetra-n-butylammonium-perchlorate as supporting electrolyte using DC-, cyclic voltammetry (CV), coulometry and controlled potential electrolysis (CPE). These compounds are oxidized in a one two-electron transfer process or in irreversible two successive one-electron processes to the corresponding diradical, which simaltaneously reacts with the solvent to regenerate the starting species. On the other hand the reduction products are the 5-arylidene-4-imidazolidinone-2-thiols.

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Voltammetrische Untersuchungen einiger substituierter 5-Aryliden-2-thiohydantoine in nichtwäßrigem Medium

Zusammenfassung Es wurden verschieden substituierte 5-Aryliden-2-thiohydantoine (2a–f) in Benzonitril mit 0.1M Tetra-n-butylammoniumperchlorat als Leitsalz elektrochemisch untersucht, wobei DC-, Cyclische Voltammetry (CV), Coulometrie und kontrollierte-Potential-Elektrolyse (CPE) eingesetzt wurden. Die Verbindungen wurden entweder in einem Zweielektronen-Transferprozeß oder in zwei irreversiblen Prozessen aufeinanderfolgender Einelektronen-Stufen zum entsprechenden Diradikal oxidiert, welches simultan mit dem Solvens unter Regenerierung der Startspezies reagiert. Andererseits sind die Reduktionsprodukte die 5-Aryliden-4-imidazolidinon-2-thiole.

     

Synthesis and Characterization of Novel Phthalocyanines with Four 16-Membered Diazadithia Macrocycles

Metal phthalocyanines (M = Cu, Ni, Co) 3-5 bearing four 16-membered diazadithia macrocycles at the peripheral positions were prepared. Detosylation with concentrated sulfuric acid afforded products containing both sulfonated groups on the aromatic rings of the macrocyclic substituents which are excellently soluble in water and donor sites for binding four Cu^II ions to give a pentanuclear complex.     

The solvolysis oftrans-[Co(4-Mepy)4Cl2]ClO4 in water-methanol mixtures

Summary The solvolysis of thetrans-[Co(4-Mepy)₄Cl₂]ClO₄ complex was studied in 0 to 70% v/v H₂O: MeOH mixtures at 40, 45, 50 and 55 °C. The high negative S^* values found for the complex cation under investigation, relative to that oftrans- [Co(py)₄Cl₂]⁺ reported in the literature, were attributed to the substituent methyl groups. The free energies of transfer of both the ground and the transition states were calculated from which the dominant effect of the solvent on the transition state is apparent.