Strong effects of the bridge configuration on photoinduced charge separation in rigidly linked donor-acceptor systems

✍ Scribed by Anna M. Oliver; Donald C. Craig; Michael N. Paddon-Row; Jan Kroon; Jan W. Verhoeven

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 711 KB
• Volume: 150
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(88)80421-4

✦ Synopsis

Photoinduced electron-transfer rates are reported for two pairs of rigid bichromophoric molecules 1(6)/2(6) and 1(8)/2( 8).

In the first pair electron donor and acceptor are separated by six, in the second pair by eight, carbon-carbon o bonds. While these o bonds provide an all-trans coupling path in l(6) and 1 ( 8), that path contains s-cis elements in 2 (6) and 2 (8) which -as shown by X-my structure data and by spectroscopic evidence -leads to a slight decrease in the effective, spatial donor-acceptor separation. Nevertheless, photoinduced electron transfer in each of the "stretched" compounds is about one order of magnitude faster than in the corresponding "bent" compound. This remarkable effect is interpreted as resulting from the unique ability of an alltrans array of u bonds to mediate electronic through-bond interaction (TBI). Interestingly the solvent dependence of the rate of photoinduced electron transfer is significantly larger in the "bent" systems, thus indicating that superexchange via solvent molecules becomes competitive with TBI if an all-mans array is not available.