Zur strahlungslosen Desaktivierung des tiefsten angeregten Singulett-Zustandes von 2-Alkyl-indazolen in neutraler und protonierter Form
✍ Scribed by Willy Heinzelmann
- Publisher
- John Wiley and Sons
- Year
- 1978
- Tongue
- German
- Weight
- 470 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0018-019X
No coin nor oath required. For personal study only.
✦ Synopsis
On the Mechanism of Radiationless Deactivation of the First Excited Singlet State of 2‐Alkyl‐indazoles
The temperature dependence of the quantum yields of fluorescence (Φ~F~), intersystem crossing (Φ~T~) and photoreactions (Φ~R~) have been measured for several neutral and protonated 2‐alkyl‐indazoles. The experimental data (Fig. 1 and 3) can be interpreted in terms of the reaction schemes 1 and 2 with temperature independent constants for fluorescence emission and intersystem crossing and temperature dependent photochemical primary processes. Whereas at low temperatures the sum of the quantum yields of fluorescence and intersystem crossing equals 1, at higher temperatures a very efficient radiationless deactivation process takes place (Table). Based on kinetic and photochemical data it is concluded that this deactivation proceeds via a hypersurface crossing (Fig. 2) or hypersurface touching (Fig. 4) in the course of the photochemical rearrangements 1 → 2 and 4 → 5 respectively.
Similar mechanisms are expected to be responsible for the unusual internal conversion in other heterocyclic compounds.