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[2.2]Paracyclophane‐4,7,12,15‐tetrone, [2.2](1,4)Naphthalenophane‐4,7,14,17‐tetrone, and 1,4,8,11‐Pentacenetetrone Radical Anions − A Comparative ESR Study
Author(s) -
Wartini Alexander R.,
Valenzuela Jorge,
Staab Heinz A.,
Neugebauer Franz A.
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199802)1998:2<221::aid-ejoc221>3.0.co;2-y
Subject(s) - chemistry , unpaired electron , intramolecular force , delocalized electron , anthracene , cyclophane , radical ion , stereochemistry , photochemistry , crystallography , radical , ion , crystal structure , organic chemistry
Three types of tetrone radical anions in which two 1,4‐benzoquinone units are connected by ethano ( 1 ·− , 2 ·− ), [2.2]paracyclophane ( 3 ·− , 4 ·− ), and anthracene bridges ( 5 ·− , 6 ·− ) have been studied by ESR and ENDOR spectroscopy. The displacement of the unpaired electron over the two π moieties in the [2.2]cyclophane radical anions 1 ·− − 4 ·− and the marked difference between the first and second reduction potentials, Δ E = | E 2 0 − E 1 0 | ≥ 0.20 V, are evidence for a substantial intramolecular electronic interaction between the two electrophores. Similar Δ E data for the syn ‐ ( 3 ) and anti ‐naphthalenophanes ( 4 ) indicate that most of the intramolecular electronic interaction takes place through the [2.2]paracyclophane bridge. When ion pairing is inhibited by complexation of the cation, the unpaired electron in 5 ·− and 6 ·− is also delocalized over the whole pentacenetetrone system at temperatures as low as 160 K.