Effect of ligand substituents of mesogenic Europium(III) complexes on luminescence: quantum-chemical simulation

Quantum-chemical simulation of the mesogenic europium(III) (Eu(III)) complexes with unique structural, liquid-crystalline (LC), optical and magnetic properties is aimed for the selection of effective components for polyfunctional materials.Ambiguous relationships between the structure, composition and properties of these complexes, as well as their dependences on various factors, along with insufficiently studied physicochemical processes and mechanisms underlying their luminescent and LC properties complicate the application of these compounds.While the central Eu(III) ion and ligand environment are selected prior to their synthesis, but the structural features of the resulting compounds and the mutual influence of ligands during photoexcitation cannot be explicitly studied experimentally.In this work, the relationships between the molecular structure of Eu(III) complexes with various substituted -diketones and Lewis bases, the energies of their lowest triplet and singlet excited states, the luminescence intensity parameters, the efficiency of intramolecular energy transfer, and the values of the theoretical quantum yield were investigated using quantum-chemical methods.The calculated excited states and energy transfer rates have been used to determine the energy transfer channels.According to the calculated data, structural factors and approaches for the modification of molecular structure in order to improve luminescence efficiency of the Eu(III) complexes were evaluated.