Two π-Electrons Make the Difference: From BODIPY to BODIIM Switchable Fluorescent Dyes.

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Boron dipyrromethene (BODIPY) dyes are versatile fluorophores with broad applications.
• Tuning optical properties of BODIPY dyes typically involves peripheral functionalization.
• A need exists for novel core modifications to expand BODIPY dye capabilities.

Purpose of the Study:

• To introduce a novel 14π-electron system, BODIIM, by modifying the BODIPY core.
• To investigate the structural and photophysical properties of the new BODIIM dye.
• To explore the reactivity and potential applications of BODIIM dyes.

Main Methods:

• Synthesis of a novel boron diimidazolylmethene (BODIIM) dye.
• Density Functional Theory (DFT) calculations for electronic structure analysis.
• Spectroscopic studies to determine optical properties (absorption, emission, Stokes shift).
• Investigation of reactivity with borane and N-heterocyclic carbene.

Main Results:

• Successful synthesis of a BODIIM dye with a rigidifying BH2 entity.
• DFT calculations confirmed the electronic structure and π-electron relationship with BODIPY.
• BODIIM exhibited a dramatically increased Stokes shift (>4170 cm⁻¹) compared to BODIPY (~500 cm⁻¹).
• Demonstrated reversible fluorescence switching via borane adduct formation and subsequent decomplexation.

Conclusions:

• The novel BODIIM core offers a unique platform for developing advanced fluorophores.
• The enhanced Stokes shift and reversible switching properties suggest potential in fluorescent sensors and switches.
• BODIIM dyes represent a significant advancement over traditional BODIPY systems.