
Abstract
In this paper we investigate the photochromic ring-opening reaction of 2,2-diphenyl-5,6-benzo(2H)-chromene. In particular, we study the uncertainties and contradictions in various published reaction models using a combination of transient absorption and fluorescence spectroscopy with femtosecond time resolution. We propose a simplified reaction scheme which is in good agreement with theoretical studies. Here, photoexcitation populates a Franck-Condon state, whose fast vibrational wave packet motion, vibrational relaxation, bond-alternation and/or solvent rearrangement processes occur on the sub-picosecond timescale. Our data suggest that the resulting excited state minimum with picosecond lifetime still features structural characteristics of the closed form. Subsequently, the ring-opened photoproducts are formed in a concerted step from the excited state. The velocity of the photoreaction hence only depends on the time that the molecule needs to reach the transition region between the ground and excited states where the crucial bond breakage occurs.
Item Type: | Journal article |
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Form of publication: | Publisher's Version |
Faculties: | Physics |
Subjects: | 500 Science > 530 Physics 500 Science > 540 Chemistry |
URN: | urn:nbn:de:bvb:19-epub-22674-2 |
ISSN: | 1474-905X |
Alliance/National Licence: | This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively. |
Language: | English |
Item ID: | 22674 |
Date Deposited: | 05. Feb 2015, 08:46 |
Last Modified: | 08. May 2024, 08:21 |