Single-Step versus Stepwise Two-Electron Reduction of Polyarylpyridiniums: Insights from the Steric Switching of Redox Potential Compression was written by Fortage, Jerome;Peltier, Cyril;Perruchot, Christian;Takemoto, Yohei;Teki, Yoshio;Bedioui, Fethi;Marvaud, Valerie;Dupeyre, Gregory;Pospisil, Lubomir;Adamo, Carlo;Hromadova, Magdalena;Ciofini, Ilaria;Laine, Philippe P.;M. And the article was included in Journal of the American Chemical Society in 2012.Formula: C7H9NO This article mentions the following:
Contrary to 4,4′-dipyridinium (i.e., archetypal Me viologen), which is reduced by two single-electron transfers (stepwise reduction), the 4,1′-dipyridinium isomer (so-called “head-to-tail” isomer) undergoes two electron transfers at apparently the same potential (single-step reduction). A combined theor. and exptl. study has been undertaken to establish that the latter electrochem. behavior, also observed for other polyarylpyridinium electrophores, is due to potential compression originating in a large structural rearrangement. Three series of branched expanded pyridiniums (EPs) were prepared: N-aryl-2,4,6-triphenylpyridiniums (Ar-TP), N-aryl-2,3,4,5,6-pentaphenylpyridiniums (Ar-XP), and N-aryl-3,5-dimethyl-2,4,6-triphenylpyridinium (Ar-DMTP). The intramol. steric strain was tuned via N-pyridinio aryl group (Ar) Ph (Ph), 4-pyridyl (Py), and 4-pyridylium (qPy) and their bulky 3,5-di-Me counterparts, xylyl (Xy), lutidyl (Lu), and lutidylium (qLu), resp. Ferrocenyl subunits as internal redox references were covalently appended to representative electrophores in order to count the electrons involved in EP-centered reduction processes. Depending on the steric constraint around the N-pyridinio site, the two-electron reduction is single-step (Ar = Ph, Py, qPy) or stepwise (Ar = Xy, Lu, qLu). This steric switching of the potential compression is accurately accounted for by ab initio modeling (D. Functional Theory, DFT) that proposes a mechanism for pyramidalization of the Npyridinio atom coupled with reduction When the hybridization change of this atom is hindered (Ar = Xy, Lu, qLu), the first reduction is a one-electron process. Theory also reveals that the single-step two-electron reduction involves couples of redox isomers (electromers) displaying both the axial geometry of native EPs and the pyramidalized geometry of doubly reduced EPs. This picture is confirmed by a combined UV-vis-NIR spectroelectrochem. and time-dependent DFT study: comparison of in situ spectroelectrochem. data with the calculated electronic transitions makes it possible to both evidence the distortion and identify the predicted electromers, which play decisive roles in the electron-transfer mechanism. Last, this mechanism is further supported by in-depth anal. of the electronic structures of electrophores in their various reduction states (including electromeric forms). In the experiment, the researchers used many compounds, for example, 3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8Formula: C7H9NO).
3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8) belongs to pyridine derivatives. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Many analogues of pyridine are known where N is replaced by other heteroatoms . Substitution of one C–H in pyridine with a second N gives rise to the diazine heterocycles (C4H4N2), with the names pyridazine, pyrimidine, and pyrazine.Formula: C7H9NO