Predictive simulation of efficiently emitting mesogenic binuclear lanthanide(III) complexes by DFT, molecular...

This article presents the results of quantum-chemical simulation of the molecular structure and luminescence characteristics of some mesogenic binuclear Ln(III) complexes with substituted β-diketones and several bridging ligands using a combination of simulation techniques such as DFT, molecular dynamics, semiempirical methods, the Judd-Ofelt theory, and the Voronoi-Dirichlet polyhedra method. The relationships between the geometric parameters, structural features of the coordination polyhedra of the complexes, and their probability of exhibiting liquid-crystalline properties were analyzed, and a ligand environment for obtaining mesogenic binuclear Ln(III) complexes was proposed. Based on the calculated values of the lowest singlet and triplet excited states of the ligands, energy level diagrams were constructed, and the main channels of intramolecular energy transfer between the excited levels of ligands and Ln(III) ions were established. The probability of interionic energy transfer was considered. The calculated theoretical values of energy transfer rates and quantum yields indicated the dominant role of the first excited singlet state of the ligands and the ⁵D₄ level of the Tb(III) ion in the energy transfer process. The intramolecular energy transfer rates and luminescence quantum yields were successfully applied to rationalize the selection of a ligand environment for the subsequent rational design and experimental preparation of mesogenic complexes with intense luminescence. Hence, this article proposes an effective tool for the construction of new functional materials for optoelectronic devices.