M. M. Getsova

Thermal decomposition of lanthanum-titanium citric complexes prepared from ethylene glycol medium

The paper addresses the thermal decomposition of La-, Ti- and bimetallic La-Ti-non-crystalline citric complexes, prepared in ethylene glycol medium. The latter complex is the starting material for the effective ferroelectric La2Ti2O7 preparation by the polymerized complex method. Based on thermogravimetric analysis (DTG, DTA and TG) and identification of some of the intermediates (by elemental analysis, NMR and IR spectroscopy and X-ray diffractometry), it is established that the thermal destruction proceeds step-wise, starting with dehydration above 50–60°C, partial transformation of the citrate to aconitate up to 200°C, followed by releasing of the ethylene glycol bonded as adduct and ester (200–280°C) and decarboxilation (280–335°C). The complete destruction of the organic components results in mixed-metal oxocarbonate. The process is completed at ∼750°C giving poorly crystalline La2Ti2O7. The results obtained are compared with those for a water-prepared NH4-La-Ti-citric complex.

Morphology and Optical Properties of SiO2-Based Composite Thin Films with Immobilized Terbium(III) Complex with a Biscoumarin Derivative

The complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methyl)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(C25H15O7)3 · 5H2O, was successfully immobilized by a simple technique in transparent SiO2-based matrix. The films and monoliths obtained were studied by IR spectroscopy, fluorescent spectroscopy, and microscopy. The micromorphology of the films was studied by atomic force microscopy, proving their homogeneity. The 3-D surface of the films is very complex geometrically and appears relatively smooth, with very fine nano-asperities spread on the surface due to the preparation process. A detailed surface description of the surface morphology at nanometer scale using statistical parameters, according to ISO 25178-2: 2012, was made. The presence of the Tb(III) complex in the films and monoliths was proven by the characteristic emission bands of the Tb(III) ions. The lifetime of the immobilized Tb(III) complex was determined, showing better protection of the SiO2 matrix in the monoliths than with the films.

Preparation and Characterization of Yttrium–Titanium Citrate Complexes

Yttrium, titanium, and yttrium-titanium citrate complexes are synthesized in ethylene glycol medium at conditions similar to those used when the polymerized complex method (a version of the sol-gel technology) is applied. The composition and IR, 1H and 13C NMR spectral characteristics of the isolated solid state complexes are studied. Proofs of the mixed metal nature of the bimetallic complexes are reported. The conditions of deprotonation of the alcoholic OH group of the citrate ligands are considered. Darstellung und Charakterisierung von Yttrium–Titan-Citratkomplexen Yttrium-, Titan- und Yttrium–Titan-Citratkomplexe wurden in Ethylenglykol unter ahnlichen Bedingungen wie bei der Komplexpolymerisation (Sol-Gel-Technik) synthetisiert. Die Zusammensetzung sowie IR-, 1H- und 13C-NMR spektroskopischen Charakteristika der isolierten festen Komplexe wurden bestimmt bzw. untersucht. Hinweise auf die gemischtmetallische Natur der Bimetallkomplexe werden angegeben. Die Bedingungen der Deprotonierung der alkoholischen OH-Gruppe der Citratliganden werden diskutiert.

On the Chemistry of Pechini Process in Cerium Containing Systems

A short summary is made about some peculiarities in the composition, spectral characteristics and thermal decomposition of cerium citric and tartaric complexes, prepared at conditions analogous to that in the polymerized complex method. The nature of the bimetallic Ce(IV)-Ti(IV)and threemetallic Y-Fe-Ce-citrates is discussed. Special attention is paid on the changes in the Ce-oxidation state depending on the nature of the salt, used as Ce-source, the ligands and the temperature of synthesis.

Synthesis of terbium(III) complex with a biscoumarin derivative and its immobilization in PMMA-based composite thin films with fluorescent properties

AbstractAn amorphous complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methylene)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(H2L)3, was successfully synthesized and characterized. IR- and 1H-NMR-spectroscopy were used to investigate the coordination of the ligand around the Tb(III) ion. Values for the quantum yield and the life time of the excited state of the complex were obtained. The complex was immobilized in transparent and flexible PMMA-based films by a simple casting technique. PMMA/chloroform solutions were used in synthetic procedures that resulted in both glass-supported and self-supporting nanocomposite films. The morphology of the films was studied by scanning electron microscopy, atomic force microscopy and transmission electron microscopy, showing the formation of crack-free films. The presence of the Tb(III) complex in the matrix was proven by the presence of characteristic bands in the IR spectra. Fluorescence microscopy and fluorescence spectroscopy demonstrated the promising optical properties of the films showing the characteristic emission bands of the Tb(III) ions. The longer life time of the excited state of the immobilized complex confirmed the protective role of the PMMA matrix on the optical properties of the complex. The composite films possessing optical properties have the potential for application as active components in optical devices.

Preparation and Characterization of Lanthanum‐Titanum Tartrate Complexes

The composition, IR, 13C and 1H NMR spectral characteristics and thermochemical behavior of La‐, Ti‐ and bimetallic La‐Ti‐tartrates (potential precursors of La2Ti2O7), obtained in ethylene glycol, were studied. The comparison of their main characteristics with those of the analogous citric complexes contributes to the elucidation of the processes involved in the complexation and thermal decomposition of such complexes. The bimetallic tartrate is a mixed‐metal complex. During heating, the complex decomposes to individual La‐ and Ti‐compounds, which interact to form La2Ti2O7 in a solid state reaction.

Micromorphology Characterization of SiO2-Based Composite Thin Films with Immobilized Terbium(III) Complex

The aim of this study was to investigate by atomic force microscopy and multifractal analysis the three-dimensional (3-D) of surface micromorphology of the complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methyl)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(C25H15O7)3 · 5H2O immobilized in transparent SiO2-based films by a simple casting technique. The 3-D surfaces contain irregularities of various orders spread on the surface due to the intrinsic method of surface preparation. We found that the micromorphology of all analyzed samples has multifractal characteristics. The generalized dimension D q and the singularity spectrum f(α) provided quantitative values that describe the degree of heterogeneity in the 3-D surface geometry at nanometer scale. The results showed that the larger the spectrum width Δα (Δα = α max − α min ) of the multifractal spectra f(α), the more nonuniform is the surface micromorphology. These results demonstrate that multifractal analysis is a more precise and reliable tool for quantitative characterization of 3-D surface micromorphology.