Isoelectronic Push-Pull Fluorescent Difluoroborates: Halogen Bonding and Photophysical Properties

Area of Science:

• Organic Chemistry
• Photophysics
• Supramolecular Chemistry

Background:

• Fluorescent dyes with push-pull topology exhibit low-lying charge-transfer (CT) excited states.
• Intermolecular interactions significantly impact the photophysical properties of these dyes.

Purpose of the Study:

• To investigate the effect of halogen bonding on the photophysical properties of novel fluorescent dyes.
• To understand how solvent interactions modulate the charge-transfer excited state.

Main Methods:

• Synthesis of fluorescent dyes and model derivatives.
• Photophysical characterization in various perfluorohaloarene solvents (e.g., C6F5I).
• Quantum-chemical calculations to support experimental findings.

Main Results:

• Halogen bonding between perfluorohaloarene solvents and the dye's heterocyclic core enhances charge-transfer in excited states.
• The position of the heterocyclic nitrogen atom influences intermolecular interaction directionality.
• Tuning of emission wavelength and fluorescence quantum yield was observed.

Conclusions:

• A direct correlation exists between molecular topology, halogen bonding interactions, and the photophysical behavior of fluorescent probes.
• Strategic design of dye structures can control intermolecular interactions for tailored photophysical properties.