Solvent polarity induced structural changes in 2,6-diamino-9,10-anthraquinone dye

Area of Science:

• Photochemistry
• Spectroscopy
• Quantum Chemistry

Background:

• Amino-substituted anthraquinone dyes are widely used.
• Understanding their photophysical properties is crucial for applications.
• Solvent effects significantly influence molecular behavior.

Purpose of the Study:

• To investigate the photophysical properties of 2,6-diamino-9,10-anthraquinone (2,6-DAAQ) in various solvents.
• To elucidate the structural basis for observed solvent-dependent behavior.
• To explore the role of solvent polarity and hydrogen bonding.

Main Methods:

• Spectroscopic measurements (absorption and fluorescence).
• Determination of fluorescence quantum yields and lifetimes.
• Ab initio quantum chemical calculations.

Main Results:

• 2,6-DAAQ shows unusual photophysical deviations in low-polarity aprotic solvents.
• The dye adopts planar intramolecular charge transfer (ICT) structures in higher polarity solvents.
• A nonplanar structure is inferred for 2,6-DAAQ in low-polarity solvents.
• Intermolecular hydrogen bonding affects properties in protic solvents.

Conclusions:

• Solvent polarity dictates the molecular structure of 2,6-DAAQ, influencing its photophysical properties.
• Structural differences, including planarity and charge transfer, explain observed spectral and fluorescence variations.
• Hydrogen bonding plays a key role in protic solvents, further modifying dye behavior.