Controlling the Host–Guest Interaction Mode through a Redox Stimulus

Abstract

A proof-of-concept related to the redox-control of the binding/releasing process in a host-guest system is achieved by designing a neutral and robust Pt-based redox-active metallacage involving two extended-tetrathiafulvalene (exTTF) ligands. When neutral, the cage is able to bind a planar polyaromatic guest (coronene). Remarkably, the chemical or electrochemical oxidation of the host-guest complex leads to the reversible expulsion of the guest outside the cavity, which is assigned to a drastic change of the host-guest interaction mode, illustrating the key role of counteranions along the exchange process. The reversible process is supported by various experimental data ( H NMR spectroscopy, ESI-FTICR, and spectroelectrochemistry) as well as by in-depth theoretical calculations performed at the density functional theory (DFT) level.

Metalla‐Assembled Electron‐Rich Tweezers: Redox‐Controlled Guest Release Through Supramolecular Dimerization

“…[4] In the course of our recent investigations in designing functional redox-active rings and cages [5] inspired by the tetrathiafulvalene (TTF) framework, [6] we recently presented ar edox-triggered guest release from electron-rich coordination cages. [7] Aside from the widely described family of coordination rings and cages that feature ac losed cavity,m olecular tweezers constitute ac lass of acyclic host molecules prone to bind various guest systems. [8] In this case,t he cavity is geometrically defined by two panels facing each other and maintained in an approximately parallel conformation by al inker.T heir guest-binding capacities depend on the inherent properties (for example,e lectronic) of their panels and on the distance separating them.…”

Strategies for Reversible Guest Uptake and Release from Metallosupramolecular Architectures

“…SallØ and co-workershave used this redox activity in tetrapyridyl-based molecules with TTF-scaffolds. [18] Depending on the substitution pattern of the pyridine rings they have either served as the guest molecule (meta-substitution, TTF1)o ra sa component of the host assembly (para-substitution, TTF2).…”

“…Initially,S allØ and coworkers coordinated their ligandsa round cis-M(dppf), (dppf = 1,1'-bis(diphenylphosphino)ferrocene) producing octacationic systems, before proceeding to investigate the difference between neutrala nd charged cages by changing the capping unit to cis-Pt(dctfb) 2 (dctfb = 3,5-dichloro-2,4,6-trifluorobenzene). [22] The authors quantitatively measured the binding of polyaromatic guests through 1 HD OSYNMR experiments,w ith the neutral cage exhibiting binding constants several orders of magnitude highert han the cationic analogue (10 5 vs. 10 2 m À1 ). Based on these results, SallØ and co-workers soughtt op robe the reversibleb inding of ap lanar polyaromatic guest (coronene), througharedox stimulus.…”

A M2L2 Redox-Active Metalla-Macrocycle Based on Electron-Rich 9-(1,3-Dithiol-2-ylidene)Fluorene

“…Beyond the synthetic challenge in preparing such objects, there is a strong interest in providing them with functionality, as encountered with recently described stimuli responsive rings and cages structures [13][14][15][16]. In this context, the preparation of redox-active metalla-rings/cages which allow a redox control over their overall charge appears relevant [17,18] and we described recently the first examples of electron-rich redox-active coordination cages capable of modulating their encapsulation properties through a redox stimulus [19,20].…”

“…In the course of our research related to the preparation of electron-rich self-assemblies [17,[19][20][21][22][23][24][25][26], we have recently demonstrated that the 9-(1,3-dithiol-2-ylidene)fluorene moiety, which is known to be readily and reversibly oxidized into a cation-radical [27,28], can be used as a building-block for the construction of electro-active self-assembled cages [29]. In line with this work, we describe herein the synthesis of an original electron-rich M 2 L 2 metalla-macrocycle constructed from the cis-blocked Pd(dppf)OTf 2 Pd(dppf)OTf2 (dppf = 1,1′-Bis(diphenylphosphino)ferrocene) acceptor and a 9-(1,3-dithiol-2-ylidene)fluorene ligand (L4Pyr) that incorporates two pyridin-4-yl units in the corresponding 3,6-positions.…”