Visible Absorption Spectrum of Benzophenone Radical Anion in Dipolar Aprotic Solvents

Abstract

Two-parameter regression including the acceptor number (AN) and permittivity (ε) of the solvent explains to some extent the solvatochromic shift of the absorption band of benzophenone radical anion (Ph2C•-O-) in the visible region. In 11 dipolar aprotic solvents characterized by ε > 10, in which the Ph2C•-O- anions are not associated with (C2H5)4N+ cations (the radicals were prepared by cathodic reduction of benzophenone in the presence of (C2H5)4N+ClO4- as electrolyte) a correlation equation has the form νmax (in cm-1) = 86.2(AN) - 19.7 · 103[(ε - 1)/(2ε + 1)] + 21.32 · 103. It reflects the relative stabilization of the ground state in a medium with a high acceptor number and an increase in the dipole moment of Ph2C•-O- during excitation.

Spectrum and Reactivity of the Solvated Electron in the Ionic Liquid Methyltributylammonium Bis(trifluoromethylsulfonyl)imide

“…Dry electron capture by pyrene provides a convenient method to estimate the initial yield of the solvated electron in R 4 NNTf 2 , on the assumption that the spectral properties of the pyrene radical anion in the ionic liquid are similar to those in molecular solvents. The 490 nm absorbance peak of the pyrene radical anion is useful for this purpose because it is very intense, there is little interference from the radical cation, and the peak occurs at the same wavelength in R 4 NNTf 2 as in other media. − Phenanthrene is not a good choice because of significant overlap of the radical anion and cation absorption bands over the accessible spectral region, and benzophenone is unsuitable because the peak wavelength of the radical anion absorption is solvent dependent. , …”

After 118 years, the isolation of two common radical anion reductants as simple, stable solids

“…These bands have been assigned to a D 0 -D 1 transition. 17,18 In conclusion, the compounds K 2 (C 10 H 8 ) 2 (THF) and neat K(Ph 2 CO) have been isolated and characterized in the solid state for the first time. Naphthalenide and benzophenone ketyl radical species are useful as strong reductants in preparative chemistry, but they have a limited shelf life in solution; moreover titration must be employed to determine exact concentrations.…”

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

“…It was proposed to ascertain whether these may accumulate, as often observed in electrochemistry [33–34] and by pulse radiolysis [35], but rarely in photochemistry.…”