Determination of the barrier to intramolecular exciplex formation in a jet-cooled, bichromophoric molecule

✍ Scribed by B. Wegewijs; R.M. Hermant; J.W. Verhoeven; A.G.M. Kunst; R.P.H. Rettschnick

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 384 KB
• Volume: 140
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(87)80492-x

✦ Synopsis

The emissive properties of a bichromophor molecule (1) are reported. This contains an anilino group as an electron donor (D) and a l-cyanonaphthalene group as an electron acceptor (A) interconnected by a saturated hydrocarbon bridge of limited flexibility, which holds D and A far apart in the electronic ground state. The emission spectrum of 1, both in solution and in the gas phase, indicates that quantitative formation of an intramolecular exciplex between D and A occurs. This exciplex formation was studied as a function of excitation energy in molecules of 1 isolated in a supersonic free jet. A barrier of 1700 + 200 cm-' was found between the Franck-Condon excited conformation and the conformation of the exciplex. Although this value is signiticantly higher than that reported earlier for exciplex formation between chromophores connected by a simple polymethylene chain ( c 900 cm-' ) it is much lower than the barrier predicted for folding the bridge in 1 sufficiently to bring D and A in close contact. A tentative explanation of this discrepancy is given.