PARAMAGNETIC REDOX STAGES OF A BISPHANE - AN ESR AND ENDOR STUDY

Seven redox stages, the dication 1(2+), the radical cation 1+, the neutral 1, the radical anion 1-, the dianion 1(2-), the radical trianion 1(3-), and the tetraanion 1(4-), are indicated by cyclic voltammetry for the bisphane 1, in which the benzene decks of two lateral paracyclophane moieties are orthogonal to the plane of anthracene framework. In 1+ and 1-, the unpaired electron is accommodated into the central anthracene subsystem, and the same statement holds for the two positive or negative charges in 1(2+) and 1(2-). Formation of 1(3-) and 1(4-) occurs through admission of additional electrons one-by-one into the two paracyclophane moieties flanking the doubly charged anthracene subsystem in 1(2-). The above-postulated, successive release or uptake of electrons by the individual parts of the bisphane is in perfect accord with the hyperfine data determined by ESR and ENDOR spectroscopy for 1+, 1-, and 1(3-), as well as for radical ions of suitable reference compounds.