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New mixed-ligand heteronuclear complexes of lanthanum and cobalt (nickel) with acetylacetone (НАА) and α,α'-dipyridyl were synthesized and investigated by physic-chemical methods of analysis (eleme...

The heterometallic acetylacetonate complex NdNi(АА)5·6Н2О has been synthesized to obtain nickel-neodymium-containing complex oxide materials. The properties of the complex have been investigated by physico-chemical methods of analysis (elemental analysis, differential thermal analysis, IR spectroscopy, X-ray powder diffraction). The data of X-ray powder diffraction and IR spectroscopy of NdNi(АА)5·6Н2О confirmed the formation of a new heterometallic single-phase compound. In the IR spectrum of NdNi(АА)5·6Н2О, a change is observed in the amount and position of the bands in the region of stretching vibrations of the М-О, CС, CО bonds, as compared to the IR spectra of the monometallic complexes Ni(AA)2·2Н2О and Nd(AA)3·3Н2О. An assessment of the thermal stability of the complex has been performed. It was shown that the synthesized heterometallic complex NdNi(АА)5·6Н2О is thermally more stable than monometallic acetylacetonates of Ni(II) and Nd(III). The heterocomplex can be used as a precursor to obtain heterometallic oxide structures. The pyrolysis of the NdNi(АА)5·6Н2О complex and, for comparison, the pyrolysis of the monocomplexes Ni(AA)2·2Н2О and Nd(AA)3·3Н2О were carried out with changing the thermolysis conditions — change of heating rate (from 5 °C/min to 20 °C/min), change of the final heating temperature (to 500 °C and to 800 °C), change of the exposure time at the final temperature (from 1 hour to 5 hours). It has been established that a change in the temperature conditions of the pyrolysis process affects the characteristics of the materials obtained (degree of amorphism, phase composition, the presence of impurities). The study of the composition of the pyrolysis products of the heterocomplex and the mixture of monometallic acetylacetonates of Ni(II) and Nd(III), obtained under heating to 800°C and holding at this temperature for 3 hours, showed the formation of a complex oxide Nd2NiO4, as well as other phases NiO, Nd6O11, Nd-Ni-O. However, their amount is noticeably smaller in the case of using a heterocomplex. It is shown that the temperature of heat treatment of the heterometallic complex and the time of its pyrolysis are much less in comparison with solid-phase synthesis methods.

This paper presents the study of mixed-ligand complexes of Ln(III), which are used as volatile precursors in CVD processes for the preparation of lanthanide-containing films and coatings. New mixed-ligand acetylacetonate complexes of lanthanides (III) with acetic (propionic) acid and acetonitrile or dimethylformamide were synthesized and investigated by physic-chemical methods of analysis (elemental analysis, differential thermal analysis, IR spectroscopy, powder X-ray diffraction). Using mixed-ligand complexation, the properties of the initial lanthanide β-diketonates (in particular, chemical and thermal stability) can be changed significantly. To assess the stability of the synthesized mixed-ligand complexes, their quantum-chemical modeling was performed using the semi-empirical method Sparkle/PM7. Standard changes of the Gibbs energy ∆G0298 were calculated for the solution reaction of (1) synthesis of mixed-ligand complexes and (2) substitution of one of the β-diketonate ligands in the Ln(III) tris-acetylacetonates dihydrates by an acetate ion or propionate ion. The ∆G0298 values for the syntesis reaction mainly increases with increasing donor basicity and decreasing ionic radii Ln(III) in the La>Gd>Lu series. For all mixed ligand complexes of Ln(III), the heats of formation are negative, which indicates their thermodynamic stability in solution. It was established that the obtained complexes have the same composition of the general formula [Ln(AA)2·L·2D], where Ln (III) = La, Gd; НАА- acetylacetonе; L - anion of acetic (HAc) or propionic (HРrop) acids, D- acetonitrile (AN), dimethylformamide (DMFA). The results of the thermal analysis confirm the computational data: in the case of the lanthanum mixed-ligand complexes, the carboxylic acid is coordinated to the central ion through bridging carboxylate-ions, which contributes to the formation of oligomers. The lanthanum mixed-ligand complexes are not volatile due to their oligomeric structure. On the other hand, similar gadolinium complexes are monomeric and sublimate at 180 - 350 °C.

Nd(III), Er(III), and Yb(III) complexes with allyl-3-oxobutanoate (allyl acetoacetate) and their phenanthroline adducts as mixed ligand complexes (MLC) are synthesized. The polycomplexes on their b...