494859-11-9Relevant articles and documents
Donor-substituted perethynylated dehydroannulenes and radiaannulenes: Acetylenic carbon sheets featuring intense intramolecular charge transfer
Mitzel, Frieder,Boudon, Corinne,Gisselbrecht, Jean-Paul,Seiler, Paul,Gross, Maurice,Diederich, Francois
, p. 1130 - 1157 (2007/10/03)
In this article, we report the preparation of unprecedented φ-conjugated macrocycles (Fig. 1) by acetylenic scaffolding using modular tetraethynylethene (TEE, 3,4-diethynylhex-3-ene-1,5-diyne) building blocks. A novel photochemical access to (Z)-bisdeprot
Photochemical trans-cis isomerisation of donor/acceptor-substituted (E)-hex-3-ene-1,5-diynes (1,2-diethynylethenes, DEEs) and 3,4-diethynylhex-3-ene-1,5-diynes (tetraethynylethenes, TEEs)
Martin, Rainer E.,Bartek, Johannes,Diederich, Francois,Tykwinski, Rik R.,Meister, Erich C.,Hilger, Anouk,Luethi, Hans Peter
, p. 233 - 241 (2007/10/03)
The photochemically reversible trans-cis isomerisation of (E)-hex-3-ene-1,5-diynes (1,2-diethynylethenes, DEEs) and 3,4-diethynylhex-3-ene-1,5-diynes (tetraethynylethenes, TEEs) substituted with electron-donating (p-dialkylaminophenyl) and/or electron-accepting (p-nitrophenyl) groups has been examined. The type and degree of donor/acceptor (D/A) functionalisation has been found to drastically affect the partial quantum yields of isomerisation Φt→c and Φc→t. Total quantum yields in n-hexane vary from Φtotal = 0.72 for a bis-acceptor substituted TEE to Φtotal, = 0.015 for a four-fold, bis-donor, bis-acceptor substituted TEE derivative. A strong relationship between Φtotal and solvent polarity as well as a strong dependence of Φt→c and Φc→t on the wavelength of excitation λexc has been observed. The temperature dependence of the photoisomerisation has been investigated for a bis-acceptor-substituted DEE and shows no changes in Φtotal over the temperature range 6.5-65 °C. None of the compounds studied undergoes thermal isomerisation at 27 °C in n-hexane. Further analysis of these compounds by theoretical investigations at the semiempirical level of theory reveals a significant reduction of the bond order of the central olefinic double bond in the D-D, D-A and A-A TEEs upon electronic excitation, thus ultimately facilitating photoisomerisation.