β-diketonates based rare-earth coordination complexes have enjoyed an expanding popularity ever since their discovery at the end of 19^th century, which spans multiple applied research fields. Their multi-faceted chemical and physical properties have been successively harnessed for liquid extraction[1], bioanalytical imaging[2] as well as in light emitting devices[3]. Yet, the fast-paced development of rare-earth β-diketonates have at times been at the expense of in-depth solutions studies, undermining the trustworthiness of synthetic procedures as occasionally pointed out at in literature[4]. Within this context, our group dedicated efforts to describe the thermodynamic features of the association of [Ln(hfac)₃(diglyme)] precursors with different (single or multi-sites) N-heterocyclic tridentate receptors, in solution[5]. The study was subsequently extended to a new series of [Ln(β-diketonates)₃X] building-blocks (where X is a glyme), based on β-diketonates ligands displaying nuanced or contrasted electronic effects. A first part of the discussion will address the preparation of these new [Ln(β-diketonates)₃X] precursors, before assessing their structural, thermodynamic and luminescent properties. Then, the propensity of these precursors to form stable ternary complexes with a N-heterocyclic tridentate ligand will be considered.

Figure 1. Crystallographic structures of selected [Ln(β-diketonates)₃diglyme] containers.