Herein, we report molecular tweezers for fullerene recognition based on 2,2’-bipyridine-bearing corannulene motifs. The syn or anti confirmation can be selected simply by Cu(I) coordination/decoordination, thus controlling the fullerene recognition...

Addressing control over molecular machines resulting in variable output modulation by mimicking nature mechanisms is a current hot topic. The exploitation of reversibility in thiol/disulfide motifs in chemical systems flanked by nonplanar corannulene moieties capable to recognize fullerenes is presented herein. Two redox-based machines have been conceived for this purpose: an ON/OFF switch that activates its binding properties upon dimerization and a self-resetting (i.e., with an automated backward process) host that substantially modulates its affinity.

CuCl·2HO and Cu(ClO)·6HO are able to promote aldol addition of pyridine-2-carboxaldehyde (pyca) with acetone, acetophenone, or cyclohexenone under neutral and mild conditions. The general and simple one-pot procedure for the aldol addition to Cu(II) complexes accesses novel Cu complexes with a large variety of different structural motifs, from which the aldol-addition ligand can be liberated by treatment with NH. Neutral heteroleptic complexes in which the ligand acts as bidentate, or homoleptic cationic complexes in which the ligand acts as tridentate can be obtained depending on the copper salt used. The key step in these reactions is the coordination of pyca to copper, which increases the electrophilic character of the aldehyde, with Cu(ClO) leading to a higher degree of activation than CuCl, as predicted by DFT calculations. A regio- and stereoselective double aldol addition of pyca in the reaction of Cu(ClO)·6HO with acetone leads to the formation of a dimer copper complex in which the novel double aldol addition product acts as a pentadentate ligand. A possible mechanism is discussed. The work is supported by extensive crystallographic studies.

The participation of the tether moiety in fullerene recognition of corannulene-based molecular tweezers is known to be an important factor. In the present work, we describe the synthesis of a set of fullerene receptors bearing two corannulene units located at a suitable distance to effectively interact with C 60 and C 70 . The tether comprises a fluorene-like scaffold where an assortment of different groups with variable electronic properties has been grafted. The photophysical and electrochemical properties of all final compounds have been unveiled and correlated to the donor/acceptor (DA) nature of the tether. Despite these strong variations, their affinity toward fullerenes cannot be correlated in any way to simple DA behavior as the main contribution to the interaction correspond to London dispersion forces. We found, however, that the sulfur-derived subfamily is able to adapt better to the fullerene outer surface slightly increasing the charge transfer and electrostatic attractive interactions being the most outstanding example the case of thiophene 4-S with C 70 as it is capable of forming a ternary 2:1 inclusion complex in solution with an electronic binding energy that offsets entropy and desolvation penalties typically associated with higher-order inclusion complexes.