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

Abstract

Developing methodologies for on‐demand control of the release of a molecular guest requires the rational design of stimuli‐responsive hosts with functional cavities. While a substantial number of responsive metallacages have already been described, the case of coordination‐tweezers has been less explored. Herein, we report the first example of a redox‐triggered guest release from a metalla‐assembled tweezer. This tweezer incorporates two redox‐active panels constructed from the electron‐rich 9‐(1,3‐dithiol‐2‐ylidene)fluorene unit that are facing each other. It dimerizes spontaneously in solution and the resulting interpenetrated supramolecular structure can dissociate in the presence of an electron‐poor planar unit, forming a 1:1 host–guest complex. This complex dissociates upon tweezer oxidation/dimerization, offering an original redox‐triggered molecular delivery pathway.

Tuning the structure and the properties of dithiafulvene metalla-assembled tweezers

“…Please do not adjust margins Please do not adjust margins observed for a DTF-based Ruthenium tweezer. 33 As expected, similar studies carried out with Pd2L4Pyr2 did not show any significant changes of the cyclic voltammogram, except a very weak anodic shift ( Figure S6).…”

“…The CV of the latter exhibits a splitting of the redox wave corresponding to the DTF units, with 2 reversible oxidations occurring at E1 ox = 0.49 V and E2 ox = 0.63 V vs Fc/Fc + , suggesting that both tips of the tweezer do not behave independently. Such splitting has already been reported in the case of molecular tweezers bearing TTF 40 and more recently with DTF tips, 33 and was ascribed to the formation of mixedvalence and π-dimer species upon oxidation. The abovementioned estimated distance of 8.5 Å between both panels in Pd2L3Pyr2 should in principle allow the sandwiching of a planar aromatic species between both tips, 41, 42 including a selfintercalation of two molecular tweezers if no other species is present in solution.…”

“…[21][22][23][24] On this basis, we described the preparation and properties of a series of redoxactive rings 25 and cages [26][27][28][29][30][31] constructed from the tetrathiafulvalene (TTF) moieties and some of its derivatives. We also recently depicted the efficiency of the 9-(1,3-dithiol-2ylidene)fluorene (DTF)-based ligands, in generating selfassembled discrete structures, be they rings 32 , tweezers 33 or cages. 34 The DTF moiety can be oxidized reversibly at low potential to the corresponding radical cation, 35,36 a species which is prone to form mixed valence or -dimer species under specific conditions.…”

“…This driving force can be exploited to control, reversibly, the release of a guest compound thanks to a redox driven dimerization process. 33 We report herein that the shape, the redox and the binding properties of coordination-driven self-assembled metalla-cycles constructed from ditopic DTF based ligands and the cis-Pd(dppf)(OTf)2 complex (dppf = 1,1'-bis-(diphenylphosphino)ferrocene; OTf = trifluoromethanesulfonate), can be efficiently and readily tuned by a simple change from a 4-pyridyl coordinating unit to a 3-pyridyl one.…”

Shape‐Adaptability and Redox‐Switching Properties of a Di‐Gold Metallotweezer

“…In fact, redox processes can be used to control de binding strength between two interacting processes, and the term ‘redox‐switch binding’ is used in reference to the change of affinity between a substrate and a host receptor upon its oxidation or reduction [17d] . To our knowledge, the only example of an effective redox‐switchable metallo‐tweezer was reported by Sallé, Goeb and co‐workers recently [18] …”