Aaron D. W. Kennedy, Isolde Sandler, Joakim Andréasson
Nov 14, 2019
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0
Influential Citations
16
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Journal
Chemistry
Abstract
Three visible-light responsive photoswitches are reported, azobis(1-methyl-benzimidazole) ( 1 ), azobis(benzoxazole) ( 2 ) and azobis(benzothiazole) ( 3 ). Photostationary distributions are obtained upon irradiation with visible light comprising ≈ 80% of the thermally unstable isomer, with thermal half-lives up to 8 min and are mostly invariant to solvent. On protonation, compound 1 H + has absorption extending beyond 600 nm, allowing switching with yellow light, and a thermal half-life just under 5 minutes. The two isomers have significantly different p K a values, offering potential as a pH switch. The absorption spectra of 2 and 3 are insensitive to acid, although changes in the thermal half-life of 3 indicate more basic intermediates that significantly influence the thermal barrier to isomerization. These findings are supported by high-level ab initio calculations which validate that protonation occurs on the ring nitrogen and that the Z isomer is more basic in all cases.