Additivity of substituent effects on the visible absorption spectra of some heteroarylazo compounds: the influence of solvent

Michael G. Hutchings, Andrew Mills

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Pronounced solvatochromic shifts are observed in the visible spectra of two series of heteroarylazobenzene derivatives based on m-acetylamino- and m-methyl-N,N-diethylaniline, measured in various solvents. The heteroaryl azo component of these dyes can be viewed as a thiophene ring substituted by cyano, nitro, alkoxycarbonyl, or ring aza (to give thiazole and isothiazole derivatives). Free-Wilson analysis has shown that the influence of each of the substituents is constant across all molecules within the two series for a given solvent. However, the substituent increments vary between different solvents and correlate with the Kamlet-Taft dipolarity/polarisability parameter pi* of the solvents. There appears to be no intuitive explanation for the relative solvent variation of different substituents, but Onsager theory suggests sensitivity to the relative size and shape of the dyes. Visible absorption maxima are predicted for unknown heteroarylazo compounds related to those studied.
Original languageEnglish
Pages (from-to)23-31
Number of pages8
JournalDyes and Pigments
Volume47
Issue number1-2
DOIs
Publication statusPublished - 4 Oct 2000

Keywords

  • heteroarylazo
  • solvatochromism
  • substituent additivity
  • Kamlet-Taft
  • Onsager theory

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