A concept for stimulated proton transfer in 1-(phenyldiazenyl)naphthalen-2-ols

Silvia Hristova, V Deneva, Michael Pittelkow, Aurelien Crochet, Fadhil S. Kamounah, Katharina M. Fromm, Poul Erik Hansen, Liudmil Antonov

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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.
Original languageEnglish
JournalDyes and Pigments
Issue numberSeptember
Pages (from-to)91-99
Number of pages9
Publication statusPublished - 1 Mar 2018


  • proton transfer
  • Dyes

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