Einelektronen‐Redox‐Reaktionen von Octamethyl[4]radialen: Nachweis der Alternanz geradzahliger Radialene

One‐Electron Redox Reactions of Octamethyl[4]radialene: Proof of the Alternancy of Even‐Membered Radialenes The photoelectron spectrum of octamethyl[4]radialene ( = tetrakis(dimethylmethylidene)cyclobutane ) yields the rather low first vertical ionization of only 7.30 eV and, therefore, the molecule can be oxidized by AlCl 3 /CH 2 Cl 2 to its radical cation. The ESR and ENDOR signal patterns recorded are almost identical with those of the radical anion, generated in a [2.2.2]cryptand THF solution by reduction at a potassium metal mirror. Their near congruency is in accord with the alternant π molecular properties of even‐membered radialenes as predicted by HMO theory, and larger changes of the D 2d structure of C 8 (CH 3 ) 8 during the redox reactions are presumably hindered by the steric overcrowding in persubstituted [4]radialenes.