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The Structure of 2,5‐Semiquinones derived from 1,6‐Bridged [ 10 ] Annulenes
Author(s) -
Gerson F.,
Müllen K.,
Vogel E.
Publication year - 1971
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19710540411
Subject(s) - annulene , chemistry , derivative (finance) , ion , stereochemistry , crystallography , organic chemistry , financial economics , economics
Abstract ESR. spectra are reported for the radical anions of the diketones I and II (see below), recently prepared from 1, 6‐methano[ 10 ]annulene and its 11, 11‐difluoro‐derivative, respectively [1]. The π‐spin populations of I⊖ and II⊖ are shown to be incompatible with the structure A an enedione‐norcaradiene. Although the alternative structure B of a [ 10 ]annulenequinone is acceptable for both I⊖ and II⊖, the ESR. data is more satisfactorily rationalized in terms of a structure ‘intermediate’ to A and B. This is particularly true for the radical anion I⊖, for which the π‐spin populations suggest a structural ‘shift’ B → A relative to II⊖. Structures A and B were postulated [1] for the neutral diketones I and II, respectively.