Impact of stereoisomer multiplicity on the luminescence analysis of europium complexes

Abstract

The present article explores the challenges arising from the extensive range of plausible stereoisomers found in europium complexes and their implications for the analysis and interpretation of luminescence data. Our main finding reveals that a wide array of plausible stereoisomer geometries, including those generated by the Complex Build Software (which outputs a proven complete set of stereoisomers, given a coordination number and polyhedron shape), can effectively fit photophysical data using regularly employed Judd-Ofelt founded luminescence formalisms. Employing such methodologies always start from a presumed input geometry, usually either solid-state crystallographic geometries, or manually constructed geometries that are later optimized using theoretical model chemistries. But our preliminary analysis of crystallographic databases identified many distinct stereoisomers from several deposited crystallographic input files of europium complexes sharing the same molecular formula. Likewise, the extensive range of theoretically possible stereoisomers available for molecular modeling frequently goes unnoticed. Unaware of this extensive range of both experimental and theoretically possible stereoisomers available, researchers run the risk of inadvertently selecting one that bears no resemblance to reality, potentially overlooking the existence of alternative configurations. Thus, utilizing what ultimately amounts to a randomly selected structure—one that may not faithfully depict the true stereoisomer present in the sample under examination—does not guarantee consistency. Adding intricacy to the matter at hand, the transition from a solid-state environment to a solution can further trigger restructuring phenomena among these stereoisomers. Nevertheless, despite these challenges, our results suggest that luminescence analysis still holds some potential for extracting valuable structural information. For instance, the geometries of cubic shape CU-8, explored for the case studies we present, were the only ones that could not be adjusted, indicating a low likelihood of accurately representing their actual structures.