Lanthanide Homobimetallic Triple‐Stranded Helicates: Insight into the Self‐Assembly Mechanism

Abstract

The self-assembly mechanism leading to the exclusive formation of a triple-stranded bimetallic helicate upon reac

Proton-assisted dissociation of a triple-stranded dinuclear europium helicate

“…11 The poor solubility below pH ¼ 6 and the precipitation of the ligand L at pH ¼ 4 prevent the determination of the other protonation constants which were estimated to be at about 5.4 for log K LH 4 and lower than 2 for log K LH 5 and log K LH6 . 15 Under very acidic conditions, below pH ¼ 2, L re-dissolves, due to protonation of the carboxylate functions.…”

“…We propose a process via the thermodynamic ''prehelicate'' Eu 2 L 2 , which is the key intermediate 11,12 of the self-assembly process mechanism of the di-europium triple-stranded helicate. The dinuclear mono-stranded Eu 2 L intermediate is less likely, since it was only observed when europium(III) was in large excess with respect to the ligand.…”

“…The dinuclear mono-stranded Eu 2 L intermediate is less likely, since it was only observed when europium(III) was in large excess with respect to the ligand. 11 It strongly suggests that the two initial protonation reactions occur on the same ligand strand and lead to the rate-limiting disentanglement of the first diprotonated ligand. The schematic representation of the dissociation mechanism is given in Fig.…”

“…10 Until now, thermodynamic, structural and spectroscopic properties of metal-containing dimetallic helicates have been extensively studied, contrary to their kinetic properties, apart from our on-going work on supramolecular edifices with polytopic ligands. [11][12][13][14] In particular, we have recently fully elucidated the self-assembly mechanism leading to the exclusive formation of a triple-stranded dimetallic helicate Eu 2 L 3 in water ( Figure S1, ESI), where L is bearing two symmetrical tridentate units (O-carboxylate, N-pyridyl, N-benzimidazolyl, Fig. 1).…”

A ferrocene-based catecholamide ligand: the consequences of ligand swivel for directed supramolecular self-assembly

“…Appropriately chosen ligand symmetries and incommensurate coordination numbers between ligand and metal can be used to direct the reversible self-assembly of complex supramolecular architectures [1][2][3][4][5]. This strategy has allowed the preparation of many metalligand based supramolecular structures such as rotaxanes and catenanes [6][7][8], helicates [9][10][11] and molecular squares, rings, grids and polyhedra [12][13][14][15][16][17][18].…”