Benzo[e][1,2,4]triazinyl, or Blatter radicals, are stable free radicals, first reported by Blatter in 1968. In contrast to their nitroxide counterparts, their properties can be modified more widely and more easily...

Electrically insulating objects gain a net electrical charge when brought in and out of contact. This phenomenon -triboelectricity -involves the flow of charged species, but to conclusively establish their nature has proven extremely difficult. Here, we demonstrate an almost linear relationship between a plastic sample's net negative charge and the amount of solution metal ions discharged to metallic particles, with a coefficient of proportionality linked to its electron affinity (stability of anionic fragments). The maximum magnitude of reductive redox work is also material-dependent: metallic particles grow to a larger extent over charged dielectrics that yield stable cationic fragments (smaller ionization energy). Importantly, the extent to which the sample can act as electron source greatly exceeds the net charging measured in a Faraday pail/electrometer set up, which brings direct evidence of triboeletricity being a mosaic of positive and negative charges rather than a homogenous ensemble, and defines for the first time their quantitative scope in electrochemistry.

Computational chemistry was used to study the N-C bond dissociation Gibbs free energies (298 K, acetonitrile) for a test set of 54 triazine derivatives, comprising combinations of 6 triazinyl radicals with 9 different alkyl leaving group. Results were obtained for homolytic cleavage of the neutral compound, and two possible mesolytic cleavage pathways for the oxidized form (cleavage to a triazinyl radical and a carbocation, or cleavage to a triazinyl cation and a carbon-centered radical). Oxidation potentials of the adducts and triazine radicals were also assessed. The aim of the study was to assess triazines as an alternative to alkoxyamines as electrochemical sources of carbon-centered radicals or cations. Oxidation potentials of the triazine adducts (-0.1 to +0.2 V vs Fc/Fc +) are lower than for corresponding alkoxyamines (0.7-1.2 V), making these compounds more functional group tolerant in electrosynthesis. In contrast to alkoxyamines, upon oxidation they generally cleave to a carbon-centered radical rather than a carbocation, and do so exergonically or at relatively low energies. Important exceptions are electron donating leaving groups for which mesolytic cleavage to a carbocation is preferred, though only in select cases is oxidative cleavage thermodynamically favored. The computational studies outlined herein support the possibility that an adduct based on the triazinyl radical is superior to an alkoxyamine for the electrochemical activation of carbon-centered radicals.