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

Abstract

We have established that bipyridinium radicals can be reversibly π-dimerized under the combined effects of chemical (proton transfer) and electrochemical (electron transfer) stimuli. Our investigations also led to the discovery that a bis-pyridinyl appended calixarene intermediate is involved in a fully reversible redox-triggered σ-dimerization process. The structure of the most stable intramolecular σ-dimer was provided by computational chemistry and its complete conversion into a noncovalent π-dimer could be triggered chemically by addition of protons, leading to the formation of protonated cation radicals. Theoretical data collected with the N-methylated and N-protonated π-dimers also support the existence of multivariant orientations in π-bonded dimers of viologen cation-radicals.

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

“…Synthesis of 5 (PF 6 ) 2 : To a solution of 4 (PF 6 ) 2 (200.0 mg, 0.32 mmol) in EtOH/CH 3 CN (1:1, 50 mL) was added 2 (90.6 mg, 0.38 mmol). The resulting mixture was allowed to stir at 80 °C for 6 h. After completion of the reaction, the mixture was evaporated under reduced pressure and the crude product was washed with dichloromethane.…”

Photo/redox-responsive 2D-Supramolecular assembly involving Cucurbit[8]uril and a star-shaped porphyrin tecton

“…Geometries have been optimized at the GGA hybrid Truhlar's density functional DFT/M06-2X level of theory [75], with a basis set 6-31G(d,p) using the Gaussian 16 revision B.01 suite of programs. This density functional is best suited to account for the dispersion interactions involved in π-dimers [26,76] and comes with a high percentage of exact exchange which is a needed feature to describe π-radicals [13].…”

“…Our group has been focusing over the past few years on the development of tailor-made redoxcontrollable molecular or supramolecular systems involving electrogenerated viologen-based -cation radicals R1VR2 +• in Figure 1B) as key responsive and/or assembling elements, using their ability to self-assemble into sandwhich-like, dimeric entities called -dimers ([(R 1 VR 2 ) 2 ] 2+ in Figure 1B) [10][11][12][13][14][15][16][17][18][19][20]. These studies, and many others [16,[21][22][23][24][25][26][27][28][29], have served to establish that the effective formation of such multi-center bonded dimers in solution actually requires either very low temperatures and/or high concentrations in radicals.…”

Dynamic supramolecular polymers built from cucurbit[n]urils and viologens

“…(b), wherein charge repulsion is lowered by the one‐electron reduction of each viologen. This homo‐valent complex involving extensive orbital overlaps between two viologen cation radicals is known as a π‐dimer . Ternary hetero‐caviplexes (1:1:1) are also frequently observed with CB[8], the latter case being illustrated in Fig.…”