Aminoazobenzene derivatives with four ortho substituents with respect to the NN double bond are a relatively unexplored class of azo compounds that show promise for use as photoswitches in biology. Tetra-ortho methoxy aminoazobenzenes, in particular, can form azonium ions under physiological conditions and exhibit red-light photoswitching. Here, we report the synthesis and characterization of two ortho bromo-methoxy aminoazobenzene derivatives. These compounds form red light absorbing azonium ions but only under very acidic conditions (pH <1). While the low pKa makes the azonium form unsuitable, the neutral versions of these compounds undergo trans-to-cis photoisomerization with blue-green light and exhibit slow (τ½ ~10 min) thermal reversion and so may find applications under physiological conditions.
Keywords: azobenzene; azonium; photoisomerization; photoswitch; visible light
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Martínez-López, D.; Babalhavaeji, A.; Sampedro, D.; Woolley, A. Beilstein Arch. 2019, 201988. doi:10.3762/bxiv.2019.88.v1
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