Redox control of molecular motions in bipyridinium appended calixarenes

Abstract

A series of redox-responsive architectures featuring two bipyridinium units introduced onto the lower rim of a calixarene skeleton has been synthesized. The redox-triggered intramolecular dimerization of the reduced bipyridiniums has been investigated by electrochemistry, spectroelectrochemistry and by theoretical chemistry. The spectroscopic signature of the intramolecular dimers was found to evolve significantly with the size of the alkyl linker introduced between the calixarene skeleton and the bipyridinium units. On account of experimental data supported by theoretical calculations, these differences have been attributed to the extent of the orbital overlap in the π-dimerized species, involving either four or only two of the pyridine rings of the bipyridinium radical cations stacked in eclipsed or staggered conformations, respectively.

Redox‐Induced Molecular Metamorphism Promoting a Sol/Gel Phase Transition in a Viologen‐Based Coordination Polymer

“…The selected hinge is made of two 4,4′‐bipyridinium units linked through a propylene linker . The short, albeit flexible C3 linker allows the molecule to adopt either an extended conformations (Figure a), imposed by strong repulsive electrostatic forces between the dicationic viologen units, or a folded conformation stabilized by π‐dimerization of both electrogenerated viologen radicals (Figure b) . The concept of redox‐switchable tecton developed in the present article builds on such electron‐triggered metamorphic process.…”

Flexible Viologen Cyclophanes: Odd/Even Effects on Intramolecular Interactions

“…As observed in ar eported bis-viologen [29] or in verdazyl-based analogues, [30] smallv ariations of the geometry can greatly modify the nature of the ground state in pairs of organic radicals.I nt hese flexible boxes, the length of the spacer and its parity modifies the parallel character of the two viologens. As observed in ar eported bis-viologen [29] or in verdazyl-based analogues, [30] smallv ariations of the geometry can greatly modify the nature of the ground state in pairs of organic radicals.I nt hese flexible boxes, the length of the spacer and its parity modifies the parallel character of the two viologens.…”

Chemically and Electrochemically Triggered Assembly of Viologen Radicals: Towards Multiaddressable Molecular Switches

“…The synthesis of bipyridinium‐calixarene derivatives 6 2+ , 6 Me 2 4+ , and 6 H 2 4+ is summarized in Scheme . The synthesis of 6 Me 2 4+ has been reported in a previous article 20. The regioselective substitution of commercially available p‐tert ‐butylcalix[4]arene 1 with an excess of 1,2‐dibromoethane ( 2 ) leads to the intermediate product 3 , which is then reacted with an excess of 1‐methyl‐4‐(4′‐pyridyl)pyridinium ( 4 + ) or 4,4′‐bipyridine ( 5 ) to afford the target compounds 6 Me 2 4+ and 6 2+ , respectively.…”