Molecular Tweezers: Concepts and Applications

Abstract

Taken to the molecular level, the concept of "tweezers" opens a rich and fascinating field at the convergence of molecular recognition, biomimetic chemistry and nanomachines. Composed of a spacer bridging two interaction sites, the behaviour of molecular tweezers is strongly influenced by the flexibility of their spacer. Operating through an "induced-fit" recognition mechanism, flexible molecular tweezers select the conformation(s) most appropriate for substrate binding. Their adaptability allows them to be used in a variety of binding modes and they have found applications in chirality signalling. Rigid spacers, on the contrary, display a limited number of binding states, which lead to selective and strong substrate binding following a "lock and key" model. Exquisite selectivity may be expressed with substrates as varied as C(60) , nanotubes and natural cofactors, and applications to molecular electronics and enzyme inhibition are emerging. At the crossroad between flexible and rigid spacers, stimulus-responsive molecular tweezers controlled by ionic, redox or light triggers belong to the realm of molecular machines, and, applied to molecular tweezing, open doors to the selective binding, transport and release of their cargo. Applications to controlled drug delivery are already appearing. The past 30 years have seen the birth of molecular tweezers; the next many years to come will surely see them blooming in exciting applications.

Assembly of a π–π stack of ligands in the binding site of an acetylcholine-binding protein

“…‘Tweezer’ molecules have been used to stabilize columns of aromatic molecules48. Also, reconstitution of a discrete columnar stack of aromatic molecules has been achieved using box-shaped coordination cage47.…”

“…Not necessarily trivial, as large flat molecules have obvious disadvantages in design strategies compared with three-dimensional fragments51, but definitely a new and unexplored opportunity, where a ligand induces different opening of a ligand-binding site while establishing the same interactions with the target protein. In addition, the growing literature on ‘tweezer’ molecules48 and on biocatalytic induction of supramolecular order52 may well prove helpful in exploring the possibilities of purposely designing stacks of ligands in proteins.…”

Porphyrin tweezer receptors: Binding studies, conformational properties and applications

“…Consequently, molecular tweezers can act as receptors for a wide variety of substrates ranging from carbon materials [3,4], anions [5,6], organic [7] and inorganic cations [8] and neutral organic guests [9]. The general use and applications of molecular tweezers in the complexation of a variety of substrates has been reviewed in several accounts [10,11,12]. A review covering molecular tweezers designed for fullerenes has also been published quite recently [3].…”

Functionalization of Graphene Oxide with 9-aminoanthracene for the Adsorptive Removal of Persistent Aromatic Pollutants from Aqueous Solution

“…These interactions are a hydrophobic effect, electrostatic and electron donor-acceptor (EDA). Based on the adsorption mechanism between aromatic compounds and carbonaceous adsorbents 63 EDA interaction was proposed to be the main mechanism for adsorption of NAP, ACN, and PHN on GO-9-AA. One type of EDA interaction is π-π EDA interaction.…”