Pairing-up viologen cations and dications: a microscopic investigation of van der Waals interactions

Abstract

Polarizability and simultaneous environment effects overcome Coulomb repulsions.

Electron‐Rich, Lewis Acidic Diborane Meets N‐Heterocyclic Aromatics: Formation and Electron Transfer in Cyclophane Boranes

“…The interaction of two viologen cations or dications was previously studied theoretically . The experimentally determined solid‐state centroid‐to‐centroid distance between the two dicationic 4,4‘‐bipyridyl units in 4 amounts to only 4.0 Å, in line with the quantum chemically calculated value of 3.9 Å (B3LYP‐D3/def2‐TZVPP).…”

“…The interaction of two viologen cations or dications was previously studied theoretically. [35] The experimentally determined solid-state centroid-to-centroid distance between the two dicationic 4,4'-bipyridyl units in 4 amounts to only 4.0 ,i nl ine with the quantum chemically calculated value of 3.9 (B3LYP-D3/def2-TZVPP). The observed distance is significantly shorter than the value of 6.8 previously determined for the well-knownC BPQT 4+ + (Figure 1) and comparable to the 3.5 measured forthe related o-ExBox 4+ + system.…”

Cyclotris(paraquat‐p‐phenylenes)

“…In comparison with previously reported bipyridinium‐containing cyclophanes in their radical states, the dramatic differences in the recognition motif associated with the bipyridinium radical cations presented by this system, as determined by X‐ray crystallography, demonstrate the tunability of these radical–radical interactions, and can prove effective when incorporated in macrocyclic scaffolds involving DMP units. These findings may have implications for, and may open up new opportunities in, the design of bipyridinium‐based materials, particularly from the point of view of their conductive and magnetic properties.…”

“…In particular, the marginal overlap between the radical cationic bipyridinium units by only two α‐carbon and two β‐carbon atoms is unprecedented and may provide new insights into the manipulation and control of the self‐assembly behavior of viologen radical cations. We envision cyclotris(paraquat‐ p ‐phenylene) and its derivatives as a fruitful entry point into the fabrication of advanced mechanically interlocked molecules and supermolecules with intricate three‐dimensional features . Their redox properties also provide access to their corresponding radical forms, which open the door to further possibilities including spintronics applications …”

A self-assembled tetrathiafulvalene box

“…A similar approach was recently developed with success in the case of flexible viologen cyclophanes, through controlling the linker length between both redox units. [24][25][26] To the best of our knowledge, only one organic macrocycle 27 featuring two facing TTF moieties has been described so far. 28 This electron-rich bis (TTF)derivative, prepared in several steps through covalent synthesis, was designed to afford a distance of ca.…”