Resonance Raman spectra of radical cations of bridged diquaternary salts of 2,2′‐bipyridine

Barker, D. J.; Cooney, Ralph P.; Summers, L. A.

doi:10.1002/jrs.1250160409

Cited by 22 publications

(5 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[34] This spectrum can be simulated [18] on the basis of complete electron delocalization around the bipyridinium nucleus, including the aza N atoms and the methyl groups. [35] This behavior is consistent with a high degree of resonance stabilization of the radical [36] and, in particular, confirms that the central C À C bond acquires some degree of double-bond character, with the radical moving towards a planar geometry.…”

Section: Resultssupporting

confidence: 70%

A Spectroscopic Study of the Reduction of Geometrically Restrained Viologens

Benniston¹,

Harriman²,

Li³

et al. 2007

Chemistry A European J

View full text Add to dashboard Cite

A small series of N,N'-dimethyl-4,4'-bipyridinium dication derivatives (commonly known as viologens) has been synthesized and fully characterized; a short dialkoxy tether attached at the 3,3'-positions is used to alter the central dihedral angle. These angles were determined by both single-crystal X-ray diffraction and by computational studies made for the dication, radical cation, and neutral species in a solvent reservoir. The dihedral angle derived for the dication controls the first reduction potential, whereas the geometry of the resultant pi-radical cation determines the magnitude of the second reduction potential. The optical absorption spectra recorded for the various species, and especially those of the radical cations, and the EPR spectral parameters of the pi-radical cations also depend on the molecular geometry. In particular, the central dihedral angle influences the spin density distribution around the aromatic nucleus and, by way of comparison to the parent viologen, it has been possible to resolve the angle dependence from the inherent inductive effect of the strap. These results are considered in terms of the degree of electronic communication between the two aromatic rings, as controlled by the length of the tether.

show abstract

Section: Resultssupporting

confidence: 70%

A Spectroscopic Study of the Reduction of Geometrically Restrained Viologens

Benniston¹,

Harriman²,

Li³

et al. 2007

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…The tentative assignments of EB + , i.e., 1300-1400 cm -1 as interring stretching vibration and 1500-1600 cm -1 as ring stretching vibration are obtained according to the Stokes assignments. 38 The main conclusion of these data is that the resonance enhancement in these molecules is such that the same bands observed in the Stokes spectrum are also observed in the anti-Stokes spectrum.…”

Section: Resultsmentioning

confidence: 66%

“…The assignments are made by comparison of the anti-Stokes RRS (Figure ) spectra with the Stokes RRS spectra (Figure ). The tentative assignments of EB + , i.e., 1300−1400 cm -1 as inter-ring stretching vibration and 1500−1600 cm -1 as ring stretching vibration are obtained according to the Stokes assignments …”

Section: Resultsmentioning

confidence: 99%

Femtosecond Resonance Raman Investigation of Four Univalent Bipyridinium Radicals

and

Hopkins

1996

J. Phys. Chem.

View full text Add to dashboard Cite

Femtosecond time-resolved resonance Raman scattering (RRS) spectroscopy is used to investigate four bipyridinium radicals: methylviologen monocation MV + , benzylviologen monocation BV + , 4,4′-bipyridinium-N,N′-di(propylsulfonate) monoanion BPDPS -, and N,N′-ethylene-2,2′-bipyridinium monocation EB + . Time resolution of the dynamics of the four radicals using the 379.6 nm laser of 350 fs pulse duration is carried out by a pump and probe technique using the time-dependent transient intensity of Stokes and anti-Stokes RRS of the C-C stretching mode. It is found that the lifetime of the electronic excited state B 3u is less than 350 fs and the vibrational relaxation rates in the electronic ground state are some 2-5 ps. The possible vibrational relaxation mechanisms including the radical structure and charge effect on the vibrational relaxation are discussed. Assignments of some in-plane stretching vibrational modes for BV + and BPDPS -are tentatively made on the basis of the similarity of their molecular skeletons to those of MV 2+ , MV + , and BV 2+ . The shifts in vibrational frequency in the N-R mode are discussed according to the mass and charge effect of the substituted group R, whereas the frequency shifts in the C-C inter-ring stretching vibration upon reduction of BV 2+ to BV + are interpreted as the increase of inter-ring C-C bond order.

show abstract

“…The yellow color of the solution at this point probably can be associated with the appearance of the totally reduced form of DQ. [20][21][22][23] Surprisingly, it seems that redox species of DQ can be formed under alkaline conditions. In the absence of CB [8], higher concentrations of DQ and higher pH conditions (pH = 11 and 12) are required for the process to occur (see discussion on Fig.…”

Section: Raman Sers and Electronic Spectra Of Dqmentioning

confidence: 99%

Cucurbit[8]uril-stabilized charge transfer complexes with diquat driven by pH: a SERS study

Roldán

Sánchez-Cortés

Garcı́a-Ramos

et al. 2012

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

In this work, we have studied the pH-dependence of the formation of DQCB[8] complexes by surface-enhanced Raman scattering (SERS) spectroscopy. The SERS spectra suggest that at acidic pH CB[8] can form a binary complex with the dication DQ(+2) while at higher pH ternary complexes with the radical cation dimer (DQ(+)˙)(2) and the radical cation-dication dimer (DQ(+)˙DQ(+2)) are formed. The pH-enhanced diquat (DQ) dimerization inside the cucurbit[8]uril cavity has not been reported until now. In addition, this study provides very valuable information regarding the use of CB[8] functionalized silver nanoparticles as SERS substrate for sensing applications.

show abstract

Resonance Raman spectra of radical cations of bridged diquaternary salts of 2,2′‐bipyridine

Cited by 22 publications

References 38 publications

A Spectroscopic Study of the Reduction of Geometrically Restrained Viologens

A Spectroscopic Study of the Reduction of Geometrically Restrained Viologens

Femtosecond Resonance Raman Investigation of Four Univalent Bipyridinium Radicals

Cucurbit[8]uril-stabilized charge transfer complexes with diquat driven by pH: a SERS study

Contact Info

Product

Resources

About