Synthesis and Physicochemical Properties of Terbium(III) and Gadolinium(III) Coordination Compounds with Some Alkyloxybe
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hesis and Physicochemical Properties of Terbium(III) and Gadolinium(III) Coordination Compounds with Some Alkyloxybenzoic Acids M. A. Nazarenkoa, A. I. Oflidia,*, A. A. Nikolaeva, V. T. Panyushkina, and M. A. Magomadovab a Kuban b
State University, Krasnodar, 350040 Russia Chechen State University, Grozny, 364024 Russia *e-mail: [email protected]
Received June 26, 2020; revised June 26, 2020; accepted July 6, 2020
Abstract—New coordination compounds of terbium(III) and gadolinium(III) with alkoxybenzoic acids and 1,10-phenanthroline were prepared by the electrochemical synthesis method. The structure and some properties of the compounds synthesized were studied by IR spectroscopy and luminescence spectroscopy, as well as by thermogravimetry. Mixed-ligand complexes of terbium(III) were found to be thermally stable up to 250–300°C, which enables their deposition by thermal vacuum evaporation in the production of electroluminescent devices. The triplet energy levels of the ligands were determined, and the influence of the neutral ligand on the luminescent properties of the terbium(III) coordination compounds was evaluated. Keywords: lanthanides, alkoxybenzoic acids, 1,10-phenanthroline, complexes, luminescence
DOI: 10.1134/S1070363220110158 Many recent studies have focused on the development of luminescent materials based on coordination compounds of lanthanides in view of their potential for broad applicability in various fields of science and technology [1–4]. Variation of the structure and composition of ligands enables optimizing practical properties of complexes [3, 4]. Introduction of neutral ligands (1,10-phenanthroline, 2,2ʹ-bipyridine [5, 6]) allows filling the coordination sphere around the central metal ion and imparting useful properties to the resultant coordinatio compound. Classical chemical methods of synthesis of coordination compounds via ion exchange reactions do not always afford substances that fully meet the appropriate requirements because of possible hydrolysis, hydration, and contamination of the target product with reaction byproducts. These drawbacks are not inherent in the electrochemical method which enables single-step synthesis of compounds that are free from extraneous ions and allows varying their composition and direction of synthesis [7–9]. The electrochemical method provides direct synthesis via formation of the coordination sphere through oxidation of metals and ligands [10, 11].
Herein, we synthesized and characterized by various physicochemical methods the coordination compounds of terbium(III) and gadolinium(III) with 2,5-dimethoxybenzoic acid 1, 3,4-diethoxybenzoic acid 2, and 1,10-phenanthroline 3 and also studied the luminescence of the new complexes and the effect of the neutral ligand thereon. Comparison of the IR spectra of the coordination compounds synthesized with those of aromatic carboxylic acids 1, 2 (Table 1) shows that, in the coordination compounds with the metals, these acids occur in the ionized form. This is indicated by the appearance of absorption bands due t
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