This work continues the scientific direction devoted to the study of physicochemical properties of lanthanide coordination compounds with sulfonyl- and carbacylamidophosphates.
Previous studies have shown that lanthanide coordination compounds with CAPh and SAPh ligands have a number of useful properties, namely: high thermal stability, intense and efficient photoluminescence, magnetic properties and biological activity, which makes them promising compounds for creating functional materials for modern technologies.
A special place in the presented work is occupied by the study of anionic and cationic complexes of lanthanides, which is associated with the prospects of their use as electrically conductive solutions containing luminescent ions. Metal containing ionic liquids based on ionic complexes can be precursors for the new types of materials. Such complexes can also act as starting materials for the synthesis of heterobinuclear compounds for white electrodiodes (WLED). In the framework of this study, 20 new anionic complexes of lanthanides with monochelating sulfonylamidophosphates and two types of cations were synthesized and characterized by the means of IR, NMR (1H, 13C, 31P) and electronic spectroscopy as well as elemental, thermogravimetric, calorimetric and X-ray diffraction methods.
This work can be considered as the beginning of a new promising area of research of coordination compounds with bis-chelating carbacyl- and sulfonylamidophosphates, as these ligands provide opportunities for obtaining the new polynuclear complexes with unique physicochemical properties.
This study was the first to obtain helicate binuclear complexes with bis-chelating SAPh ligand, which were investigated by the means of infrared, NMR (1H, 13C, 31P) and electronic spectroscopy, as well as by the methods of elemental, thermogravimetric and X-ray diffraction analyses. Attempts to use these europium and terbium complexes in the WLED technology have led to the conclusion that (NHEt3)2[Ln2(L3)4] (Ln = Eu, Tb) complexes can be used as additional phosphors for the light source spectrum correction. This will significantly improve the spectral and colorimetric characteristics of the white light emitted.
An important part of this work is the study of coordination compounds based on the new bis-chelating CAPh ligand tetramethylpyridine-2,6-diyl-(iminocarbonyl)diamidophosphate. Its acid-base properties in methanol/water solution were studied, stability constants and stoichiometry of complexes at different pH values were determined.
The new CAPh ligand is water-soluble, which makes it promising in the field of biological research. After evaluation of biological activity using the computer program PASS the antitumor (antineoplastic) activity of this carbacylamidophosphate was detected. For tetramethylpyridine-2,6-diyl-(imino-carbonyl)diamidophosphate, the presence of cytotoxic effects on leukemic cells and the absence of hemolytic activity (in the range of concentrations used) were found. That allows us to conclude that further biological studies of compounds based on this ligand are appropriate.
For the first time the tridentate coordination of the ligand to the metal ion with the formation of scorpionate-type complexes was estabilished in the coordination compounds [Ln(HL5)2(NO3)]∙i-PrOH based on bis carbacylamidophosphates.
Studies of the thermal properties of all coordination compounds obtained have shown their high thermal stability (the beginning of decay is about 200 °C), which indicates the prospects for practical use of lanthanide complexes with mono- and bis-chelating carbacyl- and sulfonylamidophosphates in LED technology. And a good solubility in water opens the perspective for their practical application in biology and medicine.
Thus, the results of research conducted in this work
• supplement knowledge of the coordination and chemical properties of mono- and bis-chelating SAPh and CAPh ligands;
• deepen the understanding of the relationship between the spectral characteristics of lanthanides with the structure of complex compounds;
• encourage the development of approaches to find the most effective ligand systems based on carbacyl- and sulfonylamidophosphates for mono- and binuclear complexes of lanthanides with the desired luminescent characteristics;
• demonstrate the perspective for practical use of binuclear europium and terbium complexes with bis-chelating SAPh ligand as phosphors in the WLED technology.
