Sequential merocyanine product isomerization following femtosecond UV excitation of a spiropyran

Ann Kathrin Holm, Omar F. Mohammed, Matteo Rini, Emad Mukhtar, Erik T.J. Nibbering*, Henk Fidder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


The ring-opening dynamics of the photochromic switch 1′,3′- dihydro-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2, 2′-(2H)-indole] in tetrachloroethene is studied with both femtosecond time-resolved ultraviolet (UV)/visible and UV/mid-infrared (IR) pump-probe spectroscopy. During the first picosecond we identify two new transient features in the UV/vis experiments, the first of which we assign to spiropyran S 1 → Sn absorption (lifetime ≤ 0.2 ps). The second feature (lifetime 0.5 ± 0.2 ps) we tentatively assign to the merocyanine T2 state. After 1 ps both probing methods show biexponential merocyanine formation kinetics, with average time constants of 17 ± 3 and 350 ± 20 ps. In the UV/IR experiments, the initial dynamics show more dispersion in formation times than in the UV/vis measurements, whereas the slower time constant is the same in both. A weak transient IR signal at ∼1360 cm-1 demonstrates that this biexponentiality is caused by a sequential isomerization between two merocyanine species. Lifetimes provide evidence that the merocyanine S1 state is not involved in the photochemical reaction.

Original languageEnglish (US)
Pages (from-to)8962-8968
Number of pages7
JournalJournal of Physical Chemistry A
Issue number40
StatePublished - Oct 13 2005
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


Dive into the research topics of 'Sequential merocyanine product isomerization following femtosecond UV excitation of a spiropyran'. Together they form a unique fingerprint.

Cite this