SIMULATION OF LUMINESCENCE INTENSITY PARAMETERS OF EUROPIUM(III) COMPLEXES ACCORDING TO THE JUDD-OFELT THEORY

Distinctive optical characteristics of the lanthanide(III) (Ln(III)) complexes, including a wide range of monochromatic luminescence wavelengths, unique mechanisms of its occurrence and related photophysical processes, determine their application in optical, optoelectronic and telecommunication devices, solar and thermoelectric elements, light emitting diodes, lasers and optical fibers. However, the high efforts and significant costs of the synthesis and experimental study of the physicochemical properties of Ln(III) compounds stimulate the use of quantum-chemical simulation methods and theoretical approaches for preliminary analysis and selection of compounds with improved characteristics prior to their synthesis. In this work, methods for the quantum-chemical simulation of the molecular structure and some optical properties of the europium(III) (Eu(III)) complexes with various β-diketones and Lewis bases were proposed. The molecular geometry of the Eu(III) complexes was optimized, geometric parameters with literary data were compared. The calculated energies of lowest singlet and triplet excited states were used to define the most probable channels of the intramolecular energy transfer and to evaluate the luminescence effectiveness of the complexes. The intensity parameters were calculated according to the Judd-Ofelt theory, on their basis the features of chemical bondings in the coordination sphere of the Eu(III) ion were analyzed and the values of the theoretical luminescence quantum yield were calculated. According to the comparison of the calculated values with experimental data, the approbation of the selected simulation methods was performed. The influence of the substitutes’ nature in ligands on the luminescence effectiveness of the Eu(III) complexes was evaluated. As a result of the analysis of the calculated optical characteristics, the restrictions and features of the applied theoretical approach for the prediction of the luminescence effectiveness of the Eu(III) complexes were studied.