Although motor proteins are essential cellular components that carry out biological processes by converting chemical energy into mechanical motion, their functions have been difficult to mimic in artificial synthetic systems. Daisy chains are a class of rotaxanes which have been targeted to serve as artificial molecular machines because their mechanically interlocked architectures enable them to contract and expand linearly, in a manner that is reminiscent of the sarcomeres of muscle tissue. The scope of external stimuli that can be used to control the musclelike motions of daisy chains remains limited, however, because of the narrow range of supramolecular motifs that have been utilized in their templated synthesis. Reported herein is a cyclic daisy chain dimer based on π-associated donor-acceptor interactions, which can be actuated with either thermal or electrochemical stimuli. Molecular dynamics simulations have shown the daisy chain's mechanism of extension/contraction in the ground state in atomistic detail.

Molecular reorganization around the core of C-60 has been achieved by electron transfer centered on pi-dimerizable viologen subunits located in a restricted region of space. Fullerene C-60 hexaadducts, featuring 12 viologen subunits, have been prepared by using copper-mediated Huisgen 1,3-dipolar cycloaddition of azides with alkynes. Detailed electrochemical studies, supported by UV-Vis and EPR spectroscopic analyses, demonstrate that the linkers bearing the viologen subunits attached to specific positions around the all-carbon sphere, allow the formation of six intramolecular pi-dimers. Theoretical calculations reveal that the close proximity of the orbitals of the viologen subunits attached to the C-60 facilitate the pi-dimerization of the bis-radical species. These investigations support the fact that the motion of discrete peripheral groups oriented around the all-carbon sphere of C-60 can be controlled electrochemically using noncovalent reversible interactions

A neutral donor-acceptor [2]rotaxane, which has been synthesized using click chemistry, has had its solid-state structure and superstructure elucidated by X-ray crystallography. Both dynamic (1)H NMR spectroscopy and electrochemical investigations have been employed in an attempt to shed light on both geometrical reorganization and redox-switching processes that are occurring or can be induced within the [2]rotaxane.

The recognition and the chemical-response properties of a bis-acridinium triphenylene receptor were investigated.