| Autor: |
Lauteslager, Xavier Y., Stokkum, Ivo H. M. van, Ramesdonk, H. John van, Bebelaar, Dick, Fraanje, Jan, Goubitz, Kees, Schenk, Henk, Brouwer, Albert M., Verhoeven, Jan W. |
| Zdroj: |
European Journal of Organic Chemistry; August 2001, Vol. 2001 Issue: 16 p3105-3118, 14p |
| Abstrakt: |
Donor−acceptor compounds containing a phenylenediamine electron donor and a naphthalene, a cyanobenzene, or a cyanonaphthalene acceptor were studied. The two chromophores are connected by three different bridging units, consisting of CH2 groups linked to a semiflexible piperidine or piperazine ring or to a rigid 2,5-diazabicyclo[2.2.1]heptane group. All donor−acceptor compounds show photoinduced charge separation, resulting in the formation of a compact charge-transfer (CCT) state in nonpolar solvents. The conformational change needed to arrive at this species is impossible in a nonpolar polymer matrix and also in methylcyclohexane at low temperature. In the cases of the piperidine- and piperazine-bridged donor−acceptor compounds, evidence for the involvement of an extended charge-transfer (ECT) species as a precursor of the CCT species was obtained from time-resolved fluorescence measurements. In contrast to harpooning systems studied previously, the energy differences between the species in the present case are so small that their interconversions are reversible within the excited state lifetimes. |
| Databáze: |
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