Intramolecular Electron Transfer between 2,5-Dimethoxy-1,4-phenylene Units in [n.n]Paracyclophane Radical Cations

✍ Scribed by Alexander R. Wartini; Jorge Valenzuela; Heinz A. Staab; Franz A. Neugebauer

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 721 KB
• Volume: 1998
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/(sici)1099-0690(199801)1998:1<139::aid-ejoc139>3.0.co;2-6

✦ Synopsis

A range of [n.n]paracyclophane radical cations (4 •+ Ϫ12 •+ ), in the higher molecular flexibility leads to a significant increase in the number of internal collisions between the electropho-which two 2,5-dimethoxy-1,4-phenylene units are connected by alkano bridges of varying length, have been studied by res, resulting in a fast (ESR time scale) intramolecular electron transfer. The intermediate [4.4]paracyclophane radical ESR and ENDOR spectroscopy. In the [2.2]-and [3.3]paracyclophane radical cations 4 •+ Ϫ6 •+ , 10 •+ and 11 •+ the delocali-cations 7 •+ and 12 •+ are apparently also localized radical cations. The close interplanar distance between the two π-moiezation of the unpaired electron over both π-moieties and the distinct difference between the first and second oxidation po-ties, however, facilitates their mutual contacts. In 7 •+ , the intramolecular electron transfer becomes fast on the ESR time tentials, ∆E = E 0 2 Ϫ E 0 1 , are evidence for a strong intramolecular electronic interaction between the two electrophores. The scale at room temperature; in 12 •+ the transfer is fast over the temperature range 200Ϫ300 K. [5.5] and [7.7] species (8 •+ and 9 •+ ) are localized radical cations at low temperature (ca. 220 K). At room temperature,