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DASA photoswitches work in chloroform if N-methyl
First-generation donor–acceptor Stenhouse adducts with a small N-methyl substituent switch well in chloroform; kinetics split photoisomerisation from cyclisation.
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What class of photochromes was studied?
Donor–acceptor Stenhouse adducts (DASAs).
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
What λmax do compounds 1–13 share in CHCl3?
567 ± 3 nm, except aniline 14 at 588 nm.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
Which isomer dominates in the dark in CDCl3?
The linear isomer a for 1–13.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
How much does DASA 1 bleach on irradiation?
94% absorbance drop, then rapid dark equilibration.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
What amine feature is a prerequisite for good switching?
A small methyl as one N-substituent.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
What cyclic fraction does aniline 14 have in the dark?
57% cyclic in chloroform.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
How were fatigue tests run?
100 cycles of 45 s irradiation and 5 min dark in chloroform.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
How far was DASA 4 cycled?
1000 times; 50% decomposition only after over 610 cycles.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
Does argon help fatigue?
Yes: DASA 2 goes from 41% to 25% decomposition after 100 cycles.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
Must both kinetic steps be fitted?
Yes—photoisomerisation and cyclisation rates are similar enough that both matter.
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified
How much higher is the dark intermediate than the linear isomer?
About 10–20 kJ mol–1 at 298 K (kd1 is 2–4 orders smaller than kd–1).
Source: Structure-function relationships of donor-acceptor Stenhouse adduct photochromic switches · DOI · quote verified