Isolation and Characterization of Phenyl Viologen as a Radical Cation and Neutral Molecule

Porter, William A.; Vaid, Thomas P.

doi:10.1021/jo050328g

Cited by 123 publications

(103 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

Section: Early Examples Of Radical Dimersmentioning

confidence: 99%

“…Some of the most common radical π-dimeric species are illustrated in Fig. 1, including the associated radical anions of singly reduced tetracyanoethylene (TCNE) [7], and the neutral radical pairs of phenalenyl [8], as well as the radical cation π-dimers of singly oxidized tetrathiafulvalene (TTF) [9,10] and singly reduced bipyridium (BIPY 2+ ) units [11,12].The π-association of phenalenyl has received much attention [8,13] as a model for the radical dimerization of large planar π-systems. The persistent (i.e., stable) neutral radical is readily generated during the oxidation of phenylene.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Molecular recognition and switching via radical dimerization

Spruell

2010

Pure and Applied Chemistry

View full text Add to dashboard Cite

This article highlights the emerging use of the interactions of radical π-dimers to drive both molecular recognition and switching processes within supramolecular systems and mechanically interlocked molecular architectures. The enhanced stability experienced by dimers of radical cation species when encapsulated, as compared to when they are free in solution, is driving their useful incorporation into functional systems. The redox stimulation used in the production of radical cation species provides the ideal trigger for molecular switching events. Moreover, the nature and strength of the radical dimerization events introduces a completely novel recognition motif within supramolecular and mechanically interlocked molecular systems, complementing well-established techniques and enabling new research opportunities to blossom.atom-centered radical dimerization and, thereafter, I will highlight the recent advances that have led to the use of this unusual class of bonding as a practical and fully orthogonal molecular recognition motif. EARLY EXAMPLES OF RADICAL DIMERSThe π-dimerization of planar radical species was first observed in the middle of the last century [1][2][3][4][5][6] in both the solid state and in concentrated solutions at low temperatures. Under these conditions, equilibria are established between two paramagnetic free radical species and a diamagnetic dimer, most often with a particular equilibrium favoring the dissociated, non-dimer state. These types of dimeric associations have been observed for a whole range of different types of planar radical species, varying in both the size of the planar systems and the charges of the dimer components. Both radical anions and cations, as well as neutral free radicals, have been observed to associate with one another in this manner. Some of the most common radical π-dimeric species are illustrated in Fig. 1, including the associated radical anions of singly reduced tetracyanoethylene (TCNE) [7], and the neutral radical pairs of phenalenyl [8], as well as the radical cation π-dimers of singly oxidized tetrathiafulvalene (TTF) [9,10] and singly reduced bipyridium (BIPY 2+ ) units [11,12].The π-association of phenalenyl has received much attention [8,13] as a model for the radical dimerization of large planar π-systems. The persistent (i.e., stable) neutral radical is readily generated during the oxidation of phenylene. Its stability can be attributed to the delocalization of the radical throughout the fused polycyclic structure, its character residing predominately on 6 of the 12 peripheral carbons [14,15]. When substituted with bulky side groups to prevent σ-binding (the radical-radical coupling to form a traditional covalent sigma (σ) bond), π-dimer formation is observed in concentrated deoxygenated solutions. Moreover, this π-dimer is comprised of two perfectly overlapping delocalized singly occupied molecular orbitals (SOMOs) on each phenalenyl unit in such a way that the two formal free radical electrons pair to form what has been described as a two-electron...

show abstract

Section: Early Examples Of Radical Dimersmentioning

confidence: 99%

mentioning

confidence: 99%

Molecular recognition and switching via radical dimerization

Spruell

2010

Pure and Applied Chemistry

View full text Add to dashboard Cite

show abstract

“…Prior studies of viologen radicals indicate that these radicals can form both sigma dimers and pi dimers (pimers), 26,28,37,42,43 although related linked viologen dication diradicals are thought to form pi dimers. 44,45 The latter pimer interaction can be thought of as deriving from the overlap of stacked π SOMO orbitals rather than via formation of a traditional σ bond.…”

mentioning

confidence: 99%

A Noncovalently Reversible Paramagnetic Switch in Water

et al. 2013

View full text Add to dashboard Cite

We report an organo-paramagnetic switch consisting of a linked bis(viologen) dication diradical that can be cycled reversibly between diamagnetic and paramagnetic states via noncovalent guest-host chemistry with cucurbit [7]uril (CB[7]) in room-temperature water. Computations suggest that the nature of the interaction between the viologen cation radical units is that of a pi dimer (pimer). Molecules with switchable magnetic properties have possible applications in spintronics, data storage devices, chemical sensors, building blocks for materials with switchable bulk magnetic properties, as well as magnetic resonance probes for biological applications. DisciplinesOrganic Chemistry | Other Chemistry | Physical Chemistry CommentsReprinted (adapted) with permission from J. Am. Chem. Soc., 2013, 135 (29) O rganic molecules with magnetic properties hold promise

show abstract

“…Comparable studies have also been carried out on isoelectronic carbon derivatives. [17] For example, tetraarylalkenes (type C), such as tetraanisylethylene, can be oxidized to afford the corresponding radical cations (type CC + ) and dication (type C 2+ ) whose structures have also been determined. [18] A common feature observed in the structure of these redox-active species is a lengthening of the boronboron bond (type B…”

mentioning

confidence: 99%