Cover Picture: Ln₃Q₉ as a Molecular Framework for Ion‐Size‐Driven Assembly of Heterolanthanide (Nd, Er, Yb) Multiple Near‐Infrared Emitters (Chem. Eur. J. 10/2015)

Abstract

The Three Graces of Canova illustrates an assembly of three entities, each carrier of its own virtue, which become one in the embrace to the central figure, governing the unit composition. Similarly, the Ln3Q9 molecular framework assembles three different NIR‐luminescent lanthanide ions, in which the central position seems to be carved out for the neodymium ion, linking all of them together by quinolinolato bridges. The multiple composition of this unit allows the individual lanthanide emissions to become combined. For more details see the Communication by F. Artizzu, P. Deplano et al. on

Energy exchange between Nd3+ and Er3+ centers within molecular complexes

“…Indeed, multinuclear Ln complexes from one step reactions frequently feature quasi-statistical distributions of the different metal types within the molecule, since they have very similar chemical behavior. 38 In the present case, the scaffold generated by LA 2− and LB 2− generates coordination sites of two distinct types (the central and the peripheral ones) that favor longer metal-to-donor bond distances in the central location, driving the binding of the larger metal to this position (see structural details below). The purity of the bulk material is supported by C, H, N microanalysis and inductively coupled plasma (ICP) metal content determinations, the latter providing a molar Nd/Er ratio of 0.53.…”

“…35 Probing Ln-to-Ln′ energy transfer (ET) within molecules is challenging because of the necessity engineer well-defined multi-metallic compounds mixing lanthanide ions with seemingly identical coordination chemistry. 36,37 Therefore, one-step self-assembly reactions involving different lanthanides often result in mixtures of metal distributions within the molecule [38][39][40][41] and thus, very tedious sequential methodologies, such as covalent linkage of preformed coordination complexes, 36,[42][43][44][45] are typically employed to obtain siteselective heterometallic Ln molecules. The synthetic procedures that are thermodynamically controlled stem from the ability to discriminate between the different metals ionic radii (rLn).…”

Distributive Nd-to-Yb Energy Transfer within Pure [YbNdYb] Heterometallic Molecules

“…Some of the valuable molecules obtained in these manners have afforded the opportunity to study for the first time interesting intramolecular Ln-to-Ln′ ET phenomena, such as Tb-to-Yb, , Tb-to-Er, or Dy-to-Tb . On the other hand, one-step reactions of self-assembly usually lead to mixtures of metal distributions within the molecule, sometimes close to statistical. − This has been used in trinuclear complexes to combine three metals in variable proportions within one molecule and tune the optical properties of the bulk mixture by modulating the proportions of the three metals employed in the reaction . The method also allowed identification of intramolecular Nd-to-Yb ET within [YbNdYb] molecules, with the inconvenient presence of molecules with the same structure but with other metal composition ( e.g.…”