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Decomposition temperatures were correlated with frequencies of valence and deformation bond vibrations in a series of N-substituted derivatives of 2,4- and 2,6-dinitroanilines (DNA). These vibrations are directly influenced by the nitro group structure and by its resonance and inductive interaction with the benzene ring. Analysis of the infrared spectra reveals a great sensitivity of the frequency and hence the CAr- NO2 bond order on the substitution character of the amino group, whereas the frequencies of the valence vibrations of theo-nitro group are influenced to a small extent only. However, at the same time the valence vibration of CAr-NO2 is a sensitive indicator of the thermal stabilities of 2,4-DNA and 2,6-DNA.

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Infrared spectra of a series of anhydrous (Rb, Cs) and hydrated (Na, K, Ca, Sr, Ba, Pb, Ag, Tl) salts of the complex anion VO(C3H2O4)2]2− were recorded and briefly discussed. The thermal behaviour of these compounds, as well as that of the corresponding diprotonated ethylenediamine cation, were investigated by TG- and DTA-methods in N2-atmosphere and complemented with studies carried out in crucible furnaces in air. Pyrolysis intermediates and residues were characterized by IR spectroscopy and overall stoichiometries for the degradation processes were proposed. In most cases orthovanadate/VO2 mixtures were obtained as final residues in N2, whereas the corresponding divanadates were produced in air.

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Abstract  

New complexes of the non-natural amino acid (p-iodo-phenylalanine) with divalent cobalt and nickel ions have been synthesized. The composition of the complexes is [M(IC6H4CH2CHNH2COO)2]2.5H2O (M=Co, Ni) and the crystal structure belongs to orthorhombic system. Infrared spectra indicate the nature of bonding in the complex. The first stage in the thermal decomposition process of the complex shows the presence of crystal water. The thermal decomposition process of cobalt complex differs from that of nickel. The intermediate and final residues in the thermal decomposition process have been analyzed to check the pyrolysis reactions. Thermal analysis indicates that the iodine atom of the ligand may coordinate to the metal ion in the lattice.

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Abstract  

Two neutral and three anionic Cr(III) complexes have been isolated from the [CrO3–non-enzymaticcellular reductants(CR)] binary and ternary systems (cellular reductant=ascorbic acid,cysteine and glutathione). Analytical data, thermal studies and infrared spectra allowed for a description of the chromium coordination sphere. Comparison with the results obtained earlier suggests strong dependence of the isolated complex composition upon the excluding Cr(VI) species.

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Alanine- and taurine-salicylal Schiff base complexes of magnesium

Synthesis, characterization and thermal decomposition

Journal of Thermal Analysis and Calorimetry
Authors: S. Luan, Y. Zhu, and Y. Jia

Abstract  

The complexes of α-alanine-salicylal Schiff base of magnesium (α-ASSM), β-alanine-salicylal Schiff base of magnesium (β-ASSM) and taurine-salicylal Schiff base of magnesium (TSSM) were synthesized. The formulae of the complexes are Mg[OC6H4CHNCH(CH3)COO]·2H2O, Mg[OC6H4CHNCH2CH2COO]·2H2O and Mg[OC6H4CHNCH2CH2SO3]·2H2O. The crystal structure belongs to orthorhombic system with the lattice parameters: a=1.6954 nm, b=2.0873 nm and c=2.3037 nm for the β-ASSM, to orthorhombic system with the lattice parameters: a=1.5586 nm, b=1.8510 nm and c=2.6240 nm for the β-ASSM, to monoclinic system with the lattice parameters: a=1.3232 nm, b=1.4960 nm, c=2.1543 nm and β=98.04° for the TSSM, respectively. The results of the thermal decomposition processes and infrared spectra of the complexes show that the complexes may possess different coordination structures.

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Abstract  

Thermal analysis (TG, DTG) and infrared absorption spectra were used to study desorption of pyridine (py), 4-methylpyridine (4-Mepy) and 4-ethylpyridine (4-Etpy) from Ni(II)-exchanged montmorillonite (Ni-MMT). It is shown that the bonds between the derivatives of pyridine (R-py) and the montmorillonite exhibit predominantly Lewis acid character. The thermal stability of studied samples and the total amounts of R-py inserted in the porous structure of Ni-MMT increase in the following sequence: py/Ni-MMT<4-Mepy/Ni-MMT<4-Etpy/Ni-MMT, i. e. the influence of the substituent on the pyridine ring is evident.

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Journal of Thermal Analysis and Calorimetry
Authors: L’. Lajdová, E. Jóna, S. Šnircová, J. Miklovič, P. Segl’a, M. Pajtášová, D. Ondrušová, and S. Mojumdar

Abstract  

The stoichiometry of thermal decomposition of the complexes Ni(NCS)2(fpy)4 (I), Ni(NCS)2(bfpy)4 (II) and Ni(NCS)2(CF3Phfpy)4 (III) (where fpy=furopyridine, bfpy=benzo-[2,3]furo[3,2-c]pyridine, CF3Phfpy=2-(3-fluoromethylphenyl) furo[3,2-c]pyridine) have been investigated in nitrogen atmosphere from room temperature to 500°C by means of TG and DTG. The results revealed that release of the heterocyclic ligands occurs in two steps. IR data suggested that fpy, bfpy and CF3Phfpy ligands were coordinated to Ni(II) through the N atom of the respective heterocyclic rings and same is the case with the anionic NCS group.

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Abstract  

Hydrated methanesulfonates Ln(CH3SO3)3 nH2O (Ln=La, Ce, Pr, Nd and Yb) and Zn(CH3SO3)2 nH2O were synthesized. The effect of atmosphere on thermal decomposition products of these methanesulfonates was investigated. Thermal decomposition products in air atmosphere of these compounds were characterized by infrared spectrometry, the content of metallic ion in thermal decomposition products were determined by complexometric titration. The results show that the thermal decomposition atmosphere has evident effect on decomposition products of hydrated La(III), Pr(III) and Nd(III) methanesulfonates, and no effect on that of hydrated Ce(III), Yb(III) and Zn(II) methanesulfonates.

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Powdered specimens were mixed with KBr in a 1:100 mass ratio and pressed with 10 ton in. −2 pressure to produce discs. Mid-infrared spectra were recorded using Digilab/Varian FTS7000 FTIR spectrometer using a resolution of 4 cm −1 averaged over 256 scans

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