Gülbanu Koyundereli Çılgı

Thermal and kinetic analysis of uranium salts

Thermal decomposition of U(C2O4)2·6H2O was studied using TG method in nitrogen, air, and oxygen atmospheres. The decomposition proceeded in five stages. The first three stages were dehydration reactions and corresponded to removal of four, one, and one mole water, respectively. Anhydrous salt decomposed to oxide products in two stages. The decomposition products in nitrogen atmosphere were different from those in air and oxygen atmospheres. In nitrogen atmosphere UO1.5(CO3)0.5 was the first product and U2O5 was the second product, while these in air and oxygen atmospheres were UO(CO3) and UO3, respectively. The second decomposition products were not stable and converted to stable oxides (nitrogen: UO2, air–oxygen: U3O8). The kinetics of each reaction was investigated with using Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa methods. These methods were combined with modeling equations for thermodynamic functions, the effective models were investigated and thermodynamic values were calculated.

Thermal and kinetic analysis of uranium salts: Part III. Uranium(IV) oxalate hydrates

The thermal decomposition kinetics of UO2C2O4·3H2O were studied by TG method in a flowing nitrogen, air, and oxygen atmospheres. It is found that UO2C2O4·3H2O decomposes to uranium oxides in four stages in all atmosphere. The first two stages are the same in the whole atmosphere that correspond to dehydration reactions. The last two stages correspond to decomposition reactions. Final decomposition products are determined with X-Ray powder diffraction method. Decomposition mechanisms are different in nitrogen atmosphere from air and oxygen atmosphere. The activation energies of all reactions were calculated by model-free (KAS and FWO) methods. For investigation of reaction models, 13 kinetic model equations were tested and correct models, giving the highest linear regression, lowest standard deviation, and agreement of activation energy value to those obtained from KAS and FWO equations were found. The optimized value of activation energy and Arrhenius factor were calculated with the best model equation. Using these values, thermodynamic functions (ΔH*, ΔS*, and ΔG*) were calculated.

Structural analysis of calix[n]arene-iron(III) complexes (n=4, 6, 8) and thermal decomposition of the parent calix[n]arenes

In this study, six new calix[n]arene-Fe3+ complexes (n = 4, 6, 8) were synthesized with parent calix[n]arenes in a DMF solution of FeCl3 · H2O. The properties and coordination characteristics of the six parent calix[n]arene-Fe3+ complexes were determined by elemental analyses, TG-DTA, UV-vis, FT-IR and 1H NMR spectroscopy. According to UV-vis analysis, in the six complexes the iron(III) coordinated by oxygen donor atoms from calix[n]arene ligands and DMF molecules. The complexes behave as 1 : 1 and 1 : 2 electrolytes in the case of calix[n]arenes (n = 4, 6) (1–4) and calix[8]arene (5, 6), respectively. 1H NMR studies demonstrate that 1 and 2 are more stable than 3, 4, 5 and 6 in DMF, and indicate cone conformation of the calix[4]arene ligands (1 and 2).

A Brief Review on the Thermal Behaviors of Calixarene-Azocalixarene Derivatives and Their Complexes

Calixarenes have been widely regarded as an important class of macrocyclic host molecules, due to their efficient and highly selective binding properties towards specific metal ions. Azocalixarenes, containing single conjugated chromophore azo (‒N˭N‒) group in p- positions are synthesized by “one-pot” procedures with satisfactory yields. Their structures (as solid and liquid) are elucidated by UV-Vis, FT-IR, 1H and 13C-NMR spectroscopic methods, as well as elemental analysis techniques. Thermal stability of calixarenes is very important because of their potential applications in high temperature processes such as the dyeing of textile fibers, ink-jet printing and photocopying and in high technology areas such as lasers and electro-optical devices. In this paper all the thermal studies of parent calix[n]arenes, azocalix[4]arene derivatives and their complexes containing lower and upper rim functionalized groups are reported. All the thermo analytical results such as the temperature ranges and peak temperatures of thermal decomposition steps and amount of volatile pyrolysis products were emphasized. The effect of substituted groups and their positions on the thermal stability of calixarenes were investigated.

The syntheses, crystal structure, thermal analysis, and anticancer activities of novel dipicolinate complexes

[Cu(pydc)(eim)3]∙H2O (1), [Cu(pydc)(4hp)(H2O)] (2), and [Ni(pydc)(3hp)(H2O)2][Cu(pydc)(3hp)(H2O)2]∙3H2O (3) (H2pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, eim = 2-ethylimidazole, 4hp = 4-hydroxypyridine, 3hp = 3-hydroxypyridine) were synthesized and characterized by elemental analysis, spectroscopic measurements (UV–vis and IR spectra), and single-crystal X-ray diffraction. Crystal analysis revealed that the complexes extended to 3-D supramolecular networks through intermolecular H-bonding and molecular interactions between the ligand moieties and water molecules. The thermal stabilities of complexes are investigated by thermogravimetry, differential thermogravimetry, and differential thermal analysis techniques. The effects of complexes on the proliferation of HT-1080 fibrosarcoma cells were investigated using the quick cell proliferation assay. The cell viability changes were found to depend on the concentrations and type of complex.

The synthesis and characterization of azocalix[4]arene based chemosensors and investigation of their properties

In the present study, azocalix[4]arenes were prepared by linking 4-methoxy, 4-methyl, 4-ethyl, 4-chloro, 4-bromo and 4-nitroaniline to calix[4]arene through a diazo-coupling reaction. A new family of azocalix[4]arene tetraester derivatives, (4a-f), have been prepared with the incorporation of ethyl ester units to azocalix[4]arene. Characterization of the synthesized azocalix[4]arenes was carried using elemental analyses, UV-vis, FT-IR and (1)H NMR spectroscopic techniques. The effect of varying pH levels and solvent types on the absorption ability of azocalix[n]arenes substituted with electron-donating and electron-withdrawing groups was examined. Thermal decomposition of azocalix[4]arene derivatives (4a-f) was investigated by means of thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA) analyses. In conclusion of the examination of the extraction we found a selectivity characteristic of these compounds toward Ag(+), Hg(+) and Hg(2+) cations.

Syntheses of crystal structures and in vitro cytotoxic activities of new copper(II) complexes of pyridine-2,6-dicarboxylate

[Cu(pydc)(im)]n (1), [Cu(pydc)(mim)3]∙2H2O (2), [Cu(pydc)(ampy)(H2O)]∙H2O (3), and [Cu(pydc)(phen)][Cu(Hpydc)2] (4) (H2pydc = 2,6-pyridinedicarboxylic acid or dipicolinic acid, im = imidazole, mim = 2-methylimidazole, ampy = 2-amino-4-methylpyridine, and phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, spectroscopic measurements (UV–vis and IR spectra) and single crystal X-ray diffraction. Complexes 1, 2 and 3 were studied by thermogravimetric analysis from ambient temperature to 1100 K under nitrogen and thermal stabilities were investigated. The effects of complexes on proliferation of fibrosarcoma cells were investigated using the Quick Cell Proliferation Assay. The cell viability changes depend on the concentrations and type of complexes. According to cell proliferation/viability data, 4 was determined to be the most cytotoxic.

Thermal Behaviors of Bisazocalix[4]arene Derivatives

ABSTRACT In this article, calix[4]arene (4) was prepared by debutylation and hydrolyses reacting from 25,27-dibenzoyl-26,28-dihydroxy-5,11,17,23-tetra(tert-butyl)calix[4]arene (2). Azocalix[4]arenes (6a-c) were coupled by linking 4-methoxy, 4-ethyl, and 4-nitroaniline to calix[4]arene (4) through a diazo-coupling reaction. Thermal behavior characteristics and decomposition routes of 25,26,27,28-tetrahydroxy-11,23-di(tert-butyl)-5,17-(p-substitue phenyl)azocalix[4]arene (6a-c) were investigated in air atmosphere by means of thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermal analysis (DTA) analyses. It was found that the decomposition of all compounds complete with two exothermic stages which corresponded to removal of substitute groups (methoxy-, ethyl-, nitro-) and second stage rest of structure decomposition.