A series of aryl azo derivatives of naphthols (1–3) were studied by means of UV–Vis and NMR spectroscopy in different solvents as well as by quantum chemical calculations and X-ray analysis. Previous studies have shown that Sudan I (1) exists as a tautomeric mixture. The effect of the solvents is minimized by the existing intramolecular hydrogen bond. Therefore, the influence on the tautomeric state in structurally modified 1 has been investigated. Structure 2 contains an additional OH-group, which deprotonates easily and affects the position of the tautomeric equilibrium by changing the electronic properties of the substituent. The implementation of a sidearm in 3 creates a condition for competition between the nitrogen from the azo group and from the piperidine unit for the tautomeric proton. In this case the use of acid as a stimulus for controlling the tautomeric process was achieved.
- azo dyes
Hristova, S., Deneva, V., Pittelkow, M., Crochet, A., Kamounah, F. S., Fromm, K. M., Hansen, P. E., & Antonov, L. (2018). A concept for stimulated proton transfer in 1-(phenyldiazenyl)naphthalen-2-ols. Dyes and Pigments, 156(September), 91-99. https://doi.org/10.1016/j.dyepig.2018.03.070