Synthesis
DOI: 10.1055/a-2701-5906
Feature

New Insight into the Photochromism of Spiropyrans: Substituent Effects on Equilibrium, Rate Constants, and Dipole Moments

Authors

  • Niklas Hermes

    1   Organic Chemistry, Department of Chemistry, University of Cologne, Cologne, Germany (Ringgold ID: RIN14309)
  • Mascha Sirin Vogt

    1   Organic Chemistry, Department of Chemistry, University of Cologne, Cologne, Germany (Ringgold ID: RIN14309)
    2   Present address: Institute of Organic Chemistry, Leibniz Universität Hannover, Schneiderberg 1b, 30167 Hannover, Germany (Ringgold ID: RIN26555)
  • Vanessa Gruber

    1   Organic Chemistry, Department of Chemistry, University of Cologne, Cologne, Germany (Ringgold ID: RIN14309)
  • Rebecca F. Maier

    1   Organic Chemistry, Department of Chemistry, University of Cologne, Cologne, Germany (Ringgold ID: RIN14309)
  • Kimia Niazkar

    1   Organic Chemistry, Department of Chemistry, University of Cologne, Cologne, Germany (Ringgold ID: RIN14309)
  • Ralf Wolfgang Giernoth

    1   Organic Chemistry, Department of Chemistry, University of Cologne, Cologne, Germany (Ringgold ID: RIN14309)


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Abstract

Spiropyrans (SPs) and merocyanines (MCs) are among the most widely used photochromic systems today. Besides solvent polarity and temperature, the electronic properties of the substituents have a significant influence on photochromic behavior. In this work, a comprehensive study on the influences of electron-donating and -withdrawing substituents at the benzopyran as well as the indole moiety of the photochromic system are elucidated. For this purpose, changes in rate constants and the shift of the SP/MC equilibrium are investigated utilizing UV/vis and NMR spectroscopy. Based on DFT calculations, a relationship between these properties and the dipole moments of the molecules is established.

Supplementary Material



Publication History

Received: 21 July 2025

Accepted after revision: 14 September 2025

Article published online:
29 September 2025

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