Dynamic lanthanide exchange between quadruple-stranded cages: the effect of ionic radius differences on kinetics and thermodynamics

Abstract

Seven different [Ln2L4]2− (Ln = La, Nd, Eu, Tb, Er, Tm and Lu) lanthanide-based quadruple-stranded helicates are here reported and transmetalation among pre-assembled cages was studied. Combining two homonuclear helicates...

Transparent and colour-neutral luminescent solar concentrators using bright Eu3+ supramolecular cages towards photovoltaic windows

“…Deprotonation of the ligand with tetraethylammonium hydroxide (TEAOH) and subsequent addition of a Eu 3+ inorganic salt leads to the selfassembly of quadruple-stranded cages. We already reported elsewhere 24,25 25 one of the two tetraethylammonium cations is hosted by the quadruple stranded cage. In such quadruple-stranded Ln 3+ cages, ligands scaffold and guest molecule can influence the formation of helicates or mesocates.…”

“…Ligands L B , L M and L A (Figure 1c) were prepared as previously reported. 24,25 The ligand L F (Figure 1c) is a modified version of L A bearing an additional -CF 2 -unit in the fluorinated terminal chains, to increase the cage solubility. This new ligand was prepared by a two steps procedure (Cu(I) catalysed N-C coupling reaction followed by a Claisen condensation) and fully characterized by NMR (Figure 2a), single crystal XRD (Figure S1, Table S1) and electrospray mass spectrometry (ESI-MS, Figure S3).…”

“…Both the ions are tetrakis-chelated by four β-diketonate groups, but Eu2 has also the nineth site occupied by an ethanol molecule. We previously 25 calculated that solvent molecules such as water and ethanol are loosely bonded to the Ln 3+ ion and hence can be present or absent according to the experimental conditions. Tables S2 and S3 report the result of the stereochemical analysis by means of continuous shape measures 27 showing that the eight-coordinated centre has a square antiprismatic coordination geometry while the nine-coordinated ion has a capped square antiprismatic coordination geometry (Figure 2d).…”

Helicate versus Mesocate in Quadruple-Stranded Lanthanide Cages: A Computational Insight

“…However, Dolphin [21] reported that the same ligand and metal can lead to the formation of both isomers, while Raymond [22] highlighted how the host-guest interaction (even with the solvent) can shift the equilibrium toward the otherwise less stable species. In this context, recently we reported a series of lanthanide [Ln 2 L 4 ] 2− quadruplestranded helicates that show interesting supramolecular properties such as ion exchange to produce heterometallic systems [23] and adaptive helicity reorganization due to a guestto-host chirality transfer [24]. We also reported a DFT study for the helicity inversion and helicate-mesocate interconversion based on a Bailar twist, which demonstrated that the ligand scaffold nature (flexibility versus rigidity) plays a crucial role on the activation energy of the intramolecular helicate twisting mechanism [24].…”

“…On the contrary, the computational literature on lanthanide-based helicates (triple-and quadruple-stranded) is quite poor. Recent studies reported Perdew-Burke-Ernzerhof (PBE) in vacuum calculations for empty quadruple-stranded helicates, with Ln(III) ions and aromatic β-diketones [30], and also, in our preview studies, the same functional with the inclusion of solvent and dispersion correction was used to reproduce the geometrical structure [23] and the isomer stability [24] of the lanthanide organic cages. In addition, molecular mechanic calculations (Sparkle/RM1 model) on quadruple-stranded dinuclear Eu(III) helicate with bis-β-diketone ligand were considered [31,32].…”