Picosecond photophysics of diphenylpolyenes: evidence for the influence of excited-state conformational changes on the energy gap ΔE(Bu*-Ag*)
✍ Scribed by C. Rullière; A. Declémy
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 527 KB
- Volume
- 135
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
B: and A: excited singlet states are directly observed in DPH (all-trans-1,6_diphenylhexatriene) and DPO (all-trans-1,8diphenyloctatetraene) using picosecond transient absorption spectroscopy. Two absorption bands near 4800 and 6500 A are observed and assigned to B: and A: excited singlet states, respectively. Time-resolved evolution, on a picosecond time scale, shows that in both DPO and DPH a thermal equilibrium exists between the B: and A: states with a non-negligible B: population at room temperature even in DPO. Temperature variations enable us to deduce the energy gap AE between these two states. It is shown that conformational changes, including the solvent cage effect, significantly influence the AJZ value which is less in the excited-state than in the ground-state conformation.