Thermodynamic Discrimination in the Formation of Tetranuclear Lanthanide Helicates

Abstract

The complexation of lanthanide cations with a tripodal ligand bearing terminal ester functions was investigated. Thermodynamic speciation was achieved by a combination of different physicochemical methods, and the stability constants of the related complexes were determined spectrophotometrically. The formation of tetranuclear 3D edifices occurs preferentially with heavier lanthanides. Their molecular structure was confirmed by X‐ray crystallography. Solid‐state luminescence properties of the EuIII and TbIII compounds were also examined.

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

“…[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

“…Not surprisingly, analogous tetranuclear complexes are obtained with L15 (Figure ), but the speciation of complexes also varies along the lanthanide series. The tetranuclear complexes [Ln 4 L15 4 ] 12+ are preferentially formed with smaller cations, but with similar thermodynamic stabilities as for the complexes with L14 (Figure ).…”

“…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 .…”

A supramolecular lanthanide separation approach based on multivalent cooperative enhancement of metal ion selectivity

“…The highly efficient recognition observed during the mixed-metal self-assembly process indicates a substantial difference in the binding affinity of L 1 toward different lanthanide ions 61 – 63 . Post-synthetic metal-metathesis experiments were conducted to shed light on the mechanism of this highly controlled metal-selective self-assembly process.…”

“…Moreover, the Ln 4 L 4 complexes assembled from the flexible ligand have rather small relative formation constants, with log β La/Eu = 0.5 and log β Tb/Lu = 1.4 (ref. 61 ). Reaction of lanthanide ions with a rigid tripodal ligand, three pcam coordination units connected with rigid triptycene moiety, generates low symmetry complexes in presence of excess ligand and a trinuclear sandwich complex [Eu 3 L 2 ] 9+ when the metal/ligand ratio [Eu]/[L] reaches 3:2 (ref.…”