ИСТИНА

Coordination compounds (CC) of lanthanides are used in many areas, such as bioimaging and organic light-emitting diodes (OLEDs). For each application, the requirements for the physicochemical properties of the CC are different. Therefore, OLED luminescent materials should demonstrate high photoluminescence quantum yield, charge carrier mobility, and high solubility as well as bioimaging materials should demonstrate solubility, high absorption and stability in solution. We suggested that heteroaromatic carboxylates possessing nitrogen in α-position relative to carboxylic group as well as high conjugation length of the ligand may increase solubility due to the decrease of polymerization degree, increase stability in solution due to better coordination and increase absorption. Therefore as anionic ligands the anions of heteroaromatic ligands presented in Figure 1 were selected, their lanthanide complexes obtained, tested in OLED as emitting layer, in luminescence thermometry and in bioimaging Syntheses of carboxylic acids were optimized and their lanthanide complexes obtained. All the europium complexes demonstrated intensive of europium ionic photoluminescence. It turned out that three-ring conjugate system possess low triplet level and small back energy transfer is observed on luminescence spectra Eu(ntz)3•3H2O as small ligand emission band. At the same time, the terbium complexes including two-ring conjugate systems demonstrate low ionic luminescence intensity due to effective back energy transfer, which is explained by high excited state energy of Tb3+. That allowed to obtain luminescent thermometers based on EuxTb1-x(L)3∙3H2O (x=1, 2,5 and 5%; L=boz and btz) compositions which shows sensitivity up to 2.8 %/K. All the complexes demonstrate solubility in several solvents up to 16 g/ml in chloroform, though complexes with three-ring ligand were less soluble that with two-ring ligands. All the complexes were tested in solution processed OLEDs in the form of mixed ligand complexes where phenantroline and bato-phenantroline were used as neutral ligands. These mixed ligand complexes were synthesized and demonstrated high europium electroluminescence intensity. Thus, the design of the lanthanide coordination compounds by means of changing degree of conjugation and introduction of a heteroatom leads to the obtainment of soluble highly luminescent complex with charge carrier mobility.