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Rationalizing substituent effects in 1-azathioxanthone photophysics.

Anne Kathrine R Junker1, Thomas Just Sørensen1

  • 1Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 København Ø, Denmark.

Methods and Applications in Fluorescence
|November 22, 2017
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Summary

Methoxy groups enhance 1-azathioxanthone dyes for efficient triplet formation, making them promising antenna chromophores for lanthanide-based dyes. Their photophysical properties are influenced by substituent effects and excited state characteristics.

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Area of Science:

  • Photochemistry
  • Materials Science
  • Organic Chemistry

Background:

  • Thioxanthones are effective triplet sensitizers, crucial for lanthanide-centered emission applications.
  • Incorporating an aza group into thioxanthones enables direct lanthanide coordination, creating potential antenna chromophores.
  • Azathioxanthones are explored as ligands for lanthanide(III) complexes in luminescent dyes.

Purpose of the Study:

  • Investigate how electron-donating methoxy substituents affect the photophysical properties of 1-azathioxanthone derivatives.
  • Synthesize novel 1-azathioxanthone compounds for efficient triplet formation and visible light absorption.
  • Evaluate the potential of these derivatives as antenna chromophores in lanthanide-based luminescent materials.

Main Methods:

  • Synthesis of three 1-azathioxanthone derivatives with methoxy substituents.
  • Characterization using absorption, emission, and time-gated emission spectroscopy.
  • Theoretical analysis employing Strickler-Berg equation, Hückel MO theory, and computational chemistry.

Main Results:

  • Methoxy groups were successfully introduced, leading to derivatives with efficient triplet formation.
  • Photophysical properties, including quantum yields and excited state lifetimes, were determined experimentally.
  • Experimental findings were rationalized by theoretical models, showing good agreement for transition energies.

Conclusions:

  • The synthesized 1-azathioxanthone derivatives exhibit promising photophysical properties for applications as antenna chromophores.
  • Electron-donating substituents significantly influence the photophysical behavior of azathioxanthones.
  • The interplay between relative energy levels and the nature of singlet/triplet excited states governs the overall photophysical characteristics.