Solvatofluorochromic Behavior of Naphthalene-Based π-Conjugated Compounds Governed by Intramolecular Charge Transfer

Area of Science:

• Materials Science
• Photochemistry
• Organic Chemistry

Background:

• Solvatofluorochromic compounds exhibit fluorescence sensitive to solvent polarity.
• Understanding structure-fluorescence relationships is key for applications in molecular sensing and optoelectronics.
• Limited understanding exists regarding the governing structure-fluorescence property relationships in these compounds.

Purpose of the Study:

• To analyze the solvatofluorochromism of seven novel naphthalene-based π-conjugated compounds.
• To investigate the relationship between compound structure and fluorescence properties in varying solvent polarities.
• To establish structure-fluorescence property relationships for naphthalene-based solvatofluorochromic materials.

Main Methods:

• Synthesis and characterization of seven novel naphthalene-based π-conjugated compounds.
• Measurement of ultraviolet-visible absorption and fluorescence spectra in six solvents.
• Determination of absolute fluorescence quantum yields and lifetimes.
• Theoretical calculations using density functional theory (DFT) and time-dependent density functional theory (TD-DFT).
• Analysis using the Lippert-Mataga equation.

Main Results:

• Five methyl ester compounds displayed significant solvatofluorochromic behavior.
• A clear relationship between Stokes shift and solvent polarity was established for these compounds.
• Theoretical calculations confirmed intramolecular charge transfer (ICT) as the mechanism behind the observed fluorescence behavior.
• The difference in dipole moments between the ground (S₀) and excited (S₁) states was quantitatively evaluated.

Conclusions:

• The study successfully established structure-fluorescence property relationships for novel naphthalene-based compounds.
• Intramolecular charge transfer is confirmed as the primary mechanism driving the solvatofluorochromic response.
• These findings advance the development of materials for molecular sensing and optoelectronic applications.