Innovative Multipodal Ligands Derived from Tröger's Bases for the Sensitization of Lanthanide(III) Luminescence

Abstract

Herein, the synthesis and characterization of the first family of multipodal ligands with a Tröger's base framework designed for the preparation of luminescent lanthanide(III) complexes are reported. Eight ligands were designed and synthesized using different strategies, including alkylation reactions, amide couplings, and Ugi multicomponent reactions. All the ligands bear carboxylate groups for the coordination of the lanthanide(III) ions, with the lanthanide(III)‐sensitizing units consisting of the Tröger's base framework itself or attached benzamides. Upon irradiation of the chromophoric ligands, green terbium(III) emission was efficiently generated, whereas europium(III) emission was negligible. The geometry and substitution pattern of the ligands allow control of the stoichiometry of the species formed and the TbIII luminescence sensitization efficiency, showing that para‐substitution patterns are more efficient than meta substitution for the formation of coordination compounds with lower TbIII/ligand ratio. We propose that the species formed are self‐assembled 2:2 or 2:4 metallosupramolecular structures.

Tröger’s Base Chemistry in Solution and in Zr(IV)-Based Metal–Organic Frameworks

“…TBs and their derivatives have historically been considered as “fascinating molecules” because of their rigid C 2 -symmetric concave-shaped scaffold that consists of two aromatic rings fused to a bicyclic aliphatic methanodiazocine unit. The unique molecular geometry with an intrinsically hydrophobic cavity has led to remarkable progress over the past few decades not only in the field of synthetically molecular designfor example, polysubstituted and heterocyclic analogs, − Trögerophanes, ,− crown ether derivatives, ,− and metal complexes − but also in diverse applications including molecular recognition, − DNA binding, − asymmetric catalysis, gas separation, ,, optical and electrical devices, ,− and drug development. , …”

Base-Catalyzed, Solvent-Free Synthesis of Rigid V-Shaped Epoxydibenzo[b,f][1,5]diazocines

“…Among the molecular building blocks mentioned above, marked interest has been focused on Tröger’s base, a small molecule with a great history (structure A in Scheme ). Its unique rigid V-shaped structure, confirmed almost 50 years after its first synthesis, has spawned an enormous number of applications in many areas, such as molecular recognition, metal catalysis, and organometallic and medicinal chemistry . The basis for widespread application arises from its trivial synthesis, carried out directly from aniline (or its derivatives) and paraformaldehyde (Scheme ).…”