Ultrafast studies of photochromic spiropyrans in solution

Journal Article · Tue Dec 29 23:00:00 EST 1992 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00053a032· OSTI ID:6200137

Zhang, J Z; Schwartz, B J; King, J C; Harris, C B ^[1]

---

1. Univ. of California, Berkeley (United States) Lawrence Berkeley Lab., CA (United States)

The photochromic reaction dynamics of the spiropyran molecule 1[prime],3[prime],3[prime]-trimethyl-6-hydroxyspiro[2H-1-benzopyran-2,2[prime]-indoline] (HBPS) in solution have been studied with picosecond and femtosecond transient electronic absorption spectroscopy. Following excitation near 300 nm, the C-O bond of the molecule breaks in less than 100 fs to form a metastable species. A small fraction of this metastable species re-forms the broken C-O bond on the time scale of 200 fs. The major fraction of the metastable photoproduct vibrationally relaxes in a few picoseconds, and then undergoes isomerization to form a merocyanine product with a decay time constant of about 100 ps, depending on solvent viscosity. This isomerization decay is faster at shorter probe wavelengths and slower at longer wavelengths, indicating that this isomerization gives rise to a red-shifted absorption spectrum. The final merocyanine isomers are stable on the nanosecond time scale. All the results indicate that the initial steps of the photochromic reaction process of HBPS are extremely fast. 52 refs., 9 figs., 1 tab.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6200137
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 114:27; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
CHEMICAL REACTIONS
DECAY
DYNAMICS
ENERGY-LEVEL TRANSITIONS
EXCITATION
HETEROCYCLIC COMPOUNDS
ISOMERIZATION
ISOMERS
MECHANICS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PYRANS
RESOLUTION
SPECTROSCOPY
TIME RESOLUTION
TIMING PROPERTIES
VISCOSITY
WAVELENGTHS