Dual Fluorescence of Fluorazene in Solution: A Computational Study

Area of Science:

• Computational Chemistry
• Photophysics
• Molecular Spectroscopy

Background:

• The fluorazene molecule is known to display dual fluorescence in polar solvents.
• Understanding its photophysical properties is crucial for applications in materials science and sensing.

Purpose of the Study:

• To theoretically investigate the absorption and emission characteristics of fluorazene in both gas and acetonitrile solution phases.
• To elucidate the molecular mechanisms underlying its dual fluorescence behavior.

Main Methods:

• Utilized complete active space second-order perturbation//complete active space self-consistent field (CASPT2//CASSCF) quantum chemical methods.
• Incorporated average solvent electrostatic potential (AVS-SCF) from molecular dynamics for accurate solvent effect modeling.

Main Results:

• Identified two optimized excited-state geometries in the gas phase: local excitation (LE) and intramolecular charge transfer (ICT).
• In acetonitrile, a planar ICT structure emerged, reducing energy differences between states.
• Calculated fluorescence energies for LE and planar ICT states show good agreement with experimental data.

Conclusions:

• The study successfully explains the dual fluorescence of fluorazene through theoretical modeling.
• Discrepancies in emission energy for the bent ICT state suggest further investigation is needed.