The thesis is devoted to the synthesis and study of the lanthanide complexes with β-ketoesters and β-diketones and determination of correlations between composition, stability and properties of obtained compounds depending on the nature of substituents in the β-dicarbonyl ligand and the electronic structure of the Ln(III) ions.
The complexation of the Ln(III) ions with acetylacetone, methyl, ethyl and allyl acetoacetate in the mixed water-organic solvents (31 metal–ligand systems, among which 21 were considered for the first time) was studied by pH-potentiometry and absorption spectroscopy. Composition, stability, existence ranges and spectral characteristics of complexes with different ligand composition were determined. It was shown that the Ln(III) β-ketoesterates are more stable in comparison with corresponding acetylacetonates because of greater value of covalent contribution in the metal–ligand bond due to higher polarizability of the β-ketoesterate ligands. The standard heats of formation reactions of mono- and bis-complexes of La(III), Nd(III), Gd(III), Ho(III) and Lu(III) with methyl acetoacetate in solution are evaluated.
In the solid state 19 Ln(III) complexes with aliphatic β-ketoesters of general formula LnL2OH•H2O / La(meacac)2X•nCH3OH (L = meacac, etacac, alacac; X = NO3, CH3COO; n = 1, 2) and 3 complexes with methacrylacetophenone Ln(mphpd)3•2H2O (Ln = Pr, Ho, Yb), among which 15 were obtained for the first time, were synthesized. Their composition, structure, thermal and spectral-luminescent properties were determined by chemical and thermal analysis, IR, diffuse reflectance and luminescent spectroscopy.
Thermal destruction of the La(III) complexes with aliphatic β-ketoesters was studied by TGA-MS in the temperature range of 25–900 °C in the helium dynamic atmosphere. Main gaseous (low-molecular aldehydes, ketones, alcohols, carbon dioxide, water) and solid (lanthanum oxycarbonate or oxide) products of pyrolysis were identified.
Normal mode analysis of La(III) and Lu(III) mono-complexes with methyl, ethyl and allyl acetoacetate was performed at the PBE0/ECP46(60)MWB+DZV(d,p) level of theory. On the basis of its results band assignment of the ligand vibrations in the experimental IR spectra of the Ln(III) β-ketoesterates in the 400–1700 cm–1 region was made. It was shown that the degree of conjugation in the chelate rings of the Ln(III) complexes with β-ketoesters is lower in comparison with corresponding β-diketones. It was found that the value of π-electronic delocalization in the ligand esteric C(O)O group of the Ln(III) β-ketoesterates increases in the lanthanide series due to increase of polarization ability of the Ln(III) ion.
