ESR Spectrum of the 4,4′-Dipyridyl Radical

Abstract

The high-resolution ESR spectrum of the radical of 4,4′-dipyridyl (Tony blue) is observed and analyzed. Dipyridyl in alcoholic solution is converted into Tony blue upon irradiation with sunlight. The spectrum consists of 153 lines, each of less than 0.1 gauss width. The measurements were also extended to a partially deuterated compound of Tony blue, and the analysis was found to be in agreement with the former within the limits of observation.

E.P.R. studies and INDO calculations on the molecular structure of radicals derived from some N-alkylpyridinium salts

“…The measured nitrogen coupling constants are consistent with those usually given in the literature [10,11,25]. The assignment of coupling constants for protons 2-6 and protons 3-5 have been made on the result of MO calculations.…”

Influence of Supramolecular Interactions on Electron-Transfer Photochromism of the Crystalline Adducts of 4,4′-Bipyridine and Carboxylic Acids

“…Compound 1 belongs to a typical Tony blue, which consists of diprotonated Bpy units (Figure ). Photochromism of Tony blue has been observed previously in solution or in the solid state; however, to the best of our knowledge, there are no previous reports on the solid-state photochromism of the Tony blue-type Bpy–carboxylic acid adducts. As shown in Figure , the crystalline sample of 1 in tablet form changed from yellow to grayish purple when illuminated with a 300 W Xe lamp.…”

“…The simplest viologens are N , N ′-dihydro-4,4′-bipyridinium salts (known as Tony blue), which can be prepared by blending simply the Bpy molecule with acids. They generally bear inorganic acidic groups as anions, , and thus remain scarce owing to the limited types of inorganic acids. Organic carboxylic acids are numerous thanks to their better designability than the inorganic acids.…”

Enhanced Photoinduced Electron Transfer and Stability of Diradicals in Neutral Extended Pyridine N-Oxides

“…10 4,4′-Bipyridine (bpy) itself may receive one electron to form the bpy •− radical, which is rather unstable in air in a solution or in solid state. 11 The improved stability of the viologen radicals in air was ascribed to the increase of the electron-accepting capacity after introducing cation substituents, including a hydrogen ion (such as Tony blue) 12 and an alkyl cation (such as methyl viologen, MV 2+ ). 13 From this viewpoint, a strong electron-withdrawing atom at the N-end of bpy should also facilitate photoinduced electron transfer and the stabilizing of radicals.…”