27768-47-4Relevant academic research and scientific papers
The Viologen Cation Radical Pimer: A Case of Dispersion-Driven Bonding
Geraskina, Margarita R.,Dutton, Andrew S.,Juetten, Mark J.,Wood, Samuel A.,Winter, Arthur H.
, p. 9435 - 9439 (2017)
The π bonds between organic radicals have generated excitement as an orthogonal interaction for designing self-assembling architectures in water. A systematic investigation of the effect of the viologen cation radical structure on the strength and nature of the pimer bond is provided. A striking and unexpected feature of this π bond is that the bond strength is unchanged by substitution with electron-donating groups or withdrawing groups or with increased conjugation. Furthermore, the interaction is undiminished by sterically bulky N-alkyl groups. Theoretical modeling indicates that strong dispersion forces dominate the interaction between the radicals, rationalizing the insensitivity of the bonding interaction to substituents: The stacking of polarizable π radicals leads to attractive dispersion forces in excess of typical dispersion interactions of small molecules and helps overcome the Coulombic repulsion of bringing two cationic species into contact.
An Electron Spin Resonance, ENDOR and TRIPLE Resonance Study of Methyl-substituted N,N'-Diphenyl-4,4'-bipyridylium Dichloride Radical Cations
Evans, Jeffrey C.,Evans, Alwyn G.,Nouri-Sorkhabi, N. Hussein,Obaid, Abdullah Y.,Rowlands, Christopher C.
, p. 315 - 318 (2007/10/02)
The e.s.r. and ENDOR spectra of the radical cations of N,N'-diphenyl-4,4'-bipyridylium dichloride (DPQ), N,N'-bis-(4-methylphenyl)-4,4'-bipyridylium dichloride (p-mDPQ), N,N'-bis-(3-methylphenyl-4,4'-bipyridylium dichloride (m-mDPQ), N,N'-bis-(2-methylphenyl)-4,4'-bipyridylium dichloride (o-mDPQ), and N,N'-bis-(2,4,6-trimethylphenyl)-4,4'-bipyridylium dichloride (T-mDPQ) in methanol were studied over a range of temperatures.Values for the hyperfine coupling constants are given at -40deg C.It was found that the radical cation concentration of DPQ+., p-mDPQ+., m-mDPQ+., and o-mDPQ+. decreased with decreasing temperature, this change being reversible, whilst that of T-mDPQ+. did not.We explain the reversible change with temperature in terms of a monomer-dimer equilibrium, and the absence of such an equilibrium in the case of T-mDPQ+. as due to the lack of planarity of the molecule, because of steric hindrance between the methyl groups and the pyridyl ortho-protons.The thermodynamic constants ΔGo, SDHo, and ΔSo, obtained for the dimerisation equilibria, are reported.
