Thermodynamics, Structure and Properties of Polynuclear Lanthanide Complexes with a Tripodal Ligand: Insight into their Self‐Assembly

Abstract

Self-assembly processes between a tripodal ligand and Ln(III) cations have been investigated by means of supramolecular analytical methods. At an equimolar ratio of components, tetranuclear tetrahedral complexes are readily formed in acetonitrile. The structural analysis of the crystallographic data shows a helical wrapping of binding strands around metallic cations. The properties of this series of highly charged 3D compounds were examined by using NMR spectroscopy and optical methods in solution and in the solid state. In the presence of excess metal, a new trinuclear complex was identified. The X-ray crystal structure elucidated the coordination of metallic cations with two ligands of different conformations. By varying the metal/ligand ratio, a global speciation of this supramolecular system has been evidenced with different spectroscopic methods. In addition, these rather complicated equilibria were successfully characterised with the thermodynamic stability constants. A rational analysis of the self-assembly processes was attempted by using the thermodynamic free energy model and the impact of the ligand structure on the effective concentration is discussed.

Chiral transcription in self-assembled tetrahedral Eu4L6 chiral cages displaying sizable circularly polarized luminescence

“…Many pioneering and elegant examples with beautiful architectural formations have been developed by Bünzli, Piguet, and other researchers. However, higher order and sophisticated polynuclear architectures such as tetranuclear tetrahedral edifices 7 ─ 14 and heptanuclear clusters 15 , 16 with cavities for potential encapsulation of guests are much less explored due to the difficulty in controlling the topology and coordination geometry. Similar to linear helicates, tetrahedral cages are intrinsically chiral with either a Δ or Λ configuration at each of the four vertices.…”

“…CPL spectroscopy studies of mononuclear systems has received considerable attention in recent years, particularly in sensing chemistry 25 – 27 ; however, only a few studies have been documented regarding supramolecular polynuclear systems 15 , 28 – 30 and none are known regarding lanthanide tetrahedral cages. The latter is believed to be a result of both weak luminescence properties and instrumental inaccessibility 7 – 14 . As a result, we set off to provide some of the missing pieces of this puzzle in the chiroptical picture in order to bridge the gap between fundamental research and applications.…”

Designing Artificial 3D Helicates: Unprecedented Self‐Assembly of Homo‐octanuclear Tetrapods with Europium

“…In the complex, 24 virtual connections exist, which globally generate asufficient energy gain to overcome repulsive interactions between cations.T he overall thermodynamic balance is thus favourable for the assembly process andt he octanuclear edifice is stabilized even in metal excess, while [Eu 4 L2 4 ] 12 + with only 12 connections is destroyed. [14] In summary,t he rational design of the octanuclear edifice with europium, efficiently supported by molecular modelling, exploits axial extensions of the tetranuclearp latform investigated previously. Indeed, the treatment of L1 with europium provides octanuclear helicates [Eu 8 L1 4 ] 24 + ,t he stoichiometry and structure of which were undoubtedly confirmed by mass spectrometry and NMR analyses.…”

“…[11, 12] Recently,s everalt etranuclear tetrahedral complexes built with lanthanides have been investigated. [13][14][15] These polynuclear edifices may exhibit several functionalities such as selective host-guest interactions, [16,17] light emission in the NIR-visible region, energy transfer and conversion.I nt his context, as patial extension of the central tetrahedron in the direction of C 3 axes is ac hallenging task allowing the introduction of additional binding sites for metalliccations in order to obtain helicoidal homo-or hetero-octanuclear complexes with tetrahedral topology.T here are only few reports on octanuclear lanthanide-containing assemblies, [18] but any system exploits similar concept. Herein we report on an unprecedented strict selfassembly of an octanuclear helicate resulting from the reaction of an ew polydentate ligand L1 with europium(III).…”

Controlling the Structures of Lanthanide Complexes in Self‐Assemblies with Tripodal Ligands

“…Anchors based on single carbon atoms have been achieved by using 1,1,1‐tris(hydroxymethyl)ethane (THME) for L13 , or 1,1,1‐tris(aminomethyl)ethane (TAME) for L14 and L15 . Similarly, L16 , with two coordinating moieties per strand, was synthesised .…”