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Abstract  

The complexes of the type SnCl4(HL)·EtOH and SnCl2L2 (HL 1 : the Schiff base resulted in 1:1 condensation of isatin and aniline; HL 2 : the Schiff base resulted in 1:1 condensation of isatin and p-toluidine) have been synthesized and characterized. The thermal analysis of the new ligands and complexes has evidenced the thermal intervals of stability and also the thermal effects that accompany them. The Schiff bases thermal transformations consist in phase transitions, Carom–N bond cleavage and thermolysis processes. The different nature of the complexes generates their different thermal behaviour. The complexes lead in three steps to SnO2 and in all cases the Schiff bases degradation generates a pyrrolidone-coordinated derivative. As for the SnCl4(HL)·EtOH complexes, the SnCl4 formed during the last step is involved in two competitive processes, one consists in their volatilisation while the other one leads to SnO2. As result the SnO2 residue is smaller than the theoretically expected.

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Abstract  

The complexes of chromium and molybdenum with salicylidene-2-aminophenol (shaH2), salicylidene-2-aminoanisole (salanH2), salicylidene-2-aminoaniline (salphenH2) and biquinoline (biq) were studied using the thermogravimetric techniques. The thermal decomposition of all complexes was found to be first order reaction and the thermodynamic parameters corresponding to the different decomposition steps were reported. Molybdenum complexes were found to be more thermally stable and the order of stability was [Mo(CO)4(biq)]>[MoO(salphen)]>[MoO2(salphenH)2]>[MoO4(salan)2]>[MoO(sha)]. Similar trend was found for chromium complexes where [Cr(CO)4(biq)]>[Cr(CO)2(salphen)] >[CrO2(CO)2(shaH2)]>[CrO2(CO)2(salan)2].

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Abstract  

Tridentate ligands 2-hydroxyphenylsalicylaldimine (SAPH2), 2-hydroxyphenyl-2-hydroxy-1-naphtalaldimine (NAPH2) and Ni(II) complexes with multidentate ligand Bis-N·N′-(salicylidene)-1,3-propanediamine (LH2) as well as mononuclear complex of Cu(II) were prepared using the same multidentate ligand. Diethylamine (Et2NH), NH3 and H2O monodentate ligands were bound to these complexes coordinatively. The heat absorbed at the temperatures where these ligands thermally dissociated from the complexes were measured using the TG and DSC methods. It is assumed that the states both of the complexes with and without the monodentate ligands are solid and coordination bond energy for the monodentate ligand is calculated. It is seen that these calculated coordination bond energies are comparable with hydrogen bond energies.

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Abstract  

New Schiff bases, salicylidene- and pyridoxylidene-thyroxine have been prepared and characterized. They were labeled with99mTc. The labeling yield of the Schiff bases was over 95%. About 60% of the activity was bound to -globulin and albumin fractions when the labled compounds were incubated with a serum sample. The labeled compounds, after i.v. administration to rats, rapidly cleared from blood and excreted into the small intestine. They appeared to behave as hepatobiliary agents.

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Abstract  

The present article describes the synthesis, structural features and thermal studies of heterochelates of the type [M(SB)(benen)(H2O)]·nH2O [where H2SB=(Z)-2-(2,2,2-trifluoro-1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethylideneamino)benzoic acid, benen=bis(benzylidene)ethylenediamine and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and VO(IV)]. The Schiff base (H2SB) have been characterized on the basis of elemental analysis, IR, 1H and 13C NMR. The heterochelates have been characterized on the basis of elemental analyses, magnetic measurements, solid state conductivity measurements, IR, reflectance spectra, and thermal studies. The FAB mass spectrum of [Co(SB)(benen)(H2O)] has been carried out. The kinetic parameters such as order of reaction (n) and the energy of activation (E a) have been reported using Freeman-Carroll method. The pre-exponential factor (A), the activation entropy (ΔS #), the activation enthalpy (ΔH #) and the free energy of activation (ΔG #) have been calculated.

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Abstract  

In this communication the evaluation of eleven new metallocomplex alanine synthons bearing C2-symmetric benzyl groups with electron-donating and electron-withdrawing substituents is described. α-Methylated glycine synthons (alanine complexes) were evaluated alongside alanine synthons in order to obtain a deeper understanding of the relationship between their structures and stereochemistry of monoalkylated products and to choose several candidates for their further tests for stereospecific preparation of 6-[18F]FDOPA. Glycine-derived analogues of the complexes 3–5 are the best candidates for the development of a 6-[18F]FDOPA preparation procedure. In the model epimerisation reaction they demonstrated the best performance, much better compared to the previously described compound 2. Complexes 3, 5 and 8 are the best in asymmetric preparation of β-13C monolabelled α-aminoisobutyric acid. They have to be tested in the preparation of α-methyl amino acids like 6-[18F]-α-methylDOPA and 2-[18F]-α-methyltyrosine.

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On the oximine complexes of transitionmetals

Part CXIX. Thermal and spectral studies on Ni(Diox.H)2 type chelate compounds

Journal of Thermal Analysis and Calorimetry
Authors: Cs. Várhelyi Jr., G. Pokol, Á. Gömöry, A. Gănescu, P. Sohár, G. Liptay, and Cs. Várhelyi

Abstract  

Fourteen chelates of the type [Ni(II)(Diox.H)2], ((Diox.H)2: various α-dioximes) have been studied by means of FTIR, NMR, MS data and various thermoanalytical methods (TG, DTA, DTG, DSC). In some cases kinetic parameters of the thermal decomposition of the complexes were also calculated using Zsak’s ‘nomogram method’. The mechanism of the decomposition processes was characterised on the basis of mass spectra.

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Journal of Thermal Analysis and Calorimetry
Authors: Maria Ribeiro da Silva, N. Araújo, A. Silva, L. da Silva, N. Barros, J. Gonçalves, and M. Ribeiro da Silva

Abstract  

The standard (p 0=0.1 MPa) molar enthalpies of formation, at T=298.15 K, in the gaseous phase, for three tetradentate Schiff bases involving a N2O2 set, N,N’-bis(salicylaldehydo)cyclohexanediimine (H2salch), N,N’-bis(acetylacetone)cyclohexanediimine (H2acacch) and N,N’-bis(benzoylacetone)cyclohexanediimine (H2bzacch), were determined from their enthalpies of combustion and sublimation, obtained by static bomb calorimetry in oxygen and by the Knudsen effusion technique, respectively. The results are compared with identical parameters for related compounds previously studied, resulting from the condensation of salicylaldehyde or β-diketone with aliphatic diamines.

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Abstract  

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of two new Schiff-bases, citronellal anthranilic acid and citronellal-5-bromoanthranilic acid have been synthesized. On the basis of spectral, magnetic and thermal data, octahedral structure was assigned to all complexes [ML2(H2O)2]. Thermal decomposition of these complexes was studied by TG. Kinetic parameters, viz activation energy, E, pre-exponential factor, A, and order of reaction, n, were calculated from the TG curves using mechanistic and non-mechanistic integral equations.

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Abstract  

Mössbauer spectroscopic studies were carried out on some synthesized iron complexes of Schiff's bases. The studies have evidenced that iron/II/ and iron/III/ species were formed, and no stereoisomers were found. However, the complex of bis/acetylacetone diethylene triamine/ had shown the geometric isomers, and only the Fe/III/ species formed. Immersion of the chelate of iron bis/salicylaldehyde ethylene diamine/ in aerated distilled water for a day had resulted in the conversion of the entire iron/II/ species into the iron/III/ complexes. The exposure to atmosphere had converted a part of iron/II/ into iron/III/ and resulted in distortion of the iron/II/ chelates. This leaves a room to think that oxygen transport or absorption may bring change in the oxidation number of the central metal ion or distortion in the structural arrangements.

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