Another Photochromism of a Spironaphtoxazine Due to the Geometric Isomerization of the Open-Form

Abstract

The photodecoloration rate of colored spironaphtho[1,2-b]oxazine 2 was much slower than the corresponding [2,1-b]oxazine 1. Existence of another photochromic system between two of the open-form isomers of 2, in addition to the well-known one for 1 between the closed and the open forms, was proved.

Transient absorption spectroscopy on spiropyran monolayers using nanosecond pump—probe Brewster angle reflectometry

“…33 Similar shifts have been observed for cistrans isomerizations in terminal methine bonds of spiropyran derived merocyanines. 34 In the current case, in view of the observed spectral shifts and with knowledge of the isomerization rate between the TTC and TTT isomers of ∼10 ms, 2 we consider that the ∼20 nm shift currently observed is most likely due to isomerization from an isomer cis about the central methine to one trans about that bond. In any event, we can state with some confidence, based upon our spectroscopically resolved data, that the longer component of the kinetic traces seen presently and previously 27 is associated with the red shift.…”