Shining New Light on the Spiropyran Photoswitch: A Photocage Decides between cis–trans or Spiro-Merocyanine Isomerization

Abstract

Photochromic molecules from the spiropyran family are known to undergo light-induced interconversion between the colorless spiro-and the colored merocyanine forms. Here, we show for the first time that small structural modifications open up for an additional photoisomerization mode: reversible cis−trans isomerization of the merocyanine. Moreover, the introduction of a photocage allows for light-activated switching between the two modes.

Photo‐/Baso‐Chromisms and the Application of a Dual‐Addressable Molecular Switch

“…In addition, the absorption spectra ( Figure 1c It's reported the cis-trans isomerizationc an be triggered by light as reported in the literature. [2,46,47] By irradiating the cis-MC with blue light (20W,4 41 nm), the absorption peaks of cis-MC isomer decreaseda nd the absorption peak at 539 nm increased( Figure S3b), indicatingthe cis-MC could photo-isomerize into trans MC, in agreement with the literature report on cis-trans isomerization. [46] Because the trans MC form of SP-OX-NO 2 can convert to ring-closed form of SP quickly with blue light irradiation ( Figure S3c), the generated trans MC then transformed to ring-closed form of SP.S ot he photoinduced cis-trans isomerizationsi ndicate the structure cis-MC is truly existence after adding base to trans MC of SP-OX-NO 2 .…”

“…Multi-addressable molecular switches have attractedalot of attention recently because of their multi-stimuli responsive properties. [1][2][3][4][5][6][7] By integration of the typical molecular switches,s uch as spiropyrans, [8,9] diarylethenes, [10][11][12][13][14] azobenzenes, [15,16] oxazolidines, [17,18] etc. [19,20] into one molecule, aseries of multi-addressable molecular switches have been achieved, which not only expands the stimuli species, buta lso enriches the outputs ignals.…”

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

“…The transoid merocyanine forms do not fluoresce appreciably in water but do fluoresce in polar organic solvents. 52,[67][68][69][70] The photophysics is analogous to that of cis-and trans-stilbenes, the former being non-fluorescent and the latter weakly fluorescent (F f = 0.05). 6 While the steric interactions present in cis-stilbene favour twisting along the p-p*excited state surface (vide supra), trans-stilbene does not.…”

Shape-Memory Polymeric Artificial Muscles: Mechanisms, Applications and Challenges

“…There is also a range of other functional groups that possess photoresponsive behavior. The spiropyran molecule is distinctly sensitive to ultraviolet light and has been used to make a molecular switch ( Figure 8 a) [ 109 ]. The spiropyran structure shows three different light-response properties at three different wavelengths.…”