Photochemical "triode" molecular signal transducer

Area of Science:

• Supramolecular Chemistry
• Photochemistry
• Molecular Electronics

Background:

• Bis(phenylethynyl)anthracene (BPEA) fluorophores are known for their luminescence properties.
• Dithienylethene photochromes can switch between open and closed forms upon light irradiation.
• Molecular systems integrating multiple functional units are crucial for developing advanced optical devices.

Purpose of the Study:

• To synthesize and characterize a novel molecular hexad integrating BPEA fluorophores and a dithienylethene photochrome.
• To investigate the photophysical properties and energy transfer dynamics within the hexad.
• To demonstrate the potential of the hexad as a molecular switch analogous to a transistor.

Main Methods:

• Synthesis of a hexad comprising five BPEA units and one dithienylethene unit around a hexaphenylbenzene core.
• Time-resolved spectroscopy to study singlet-singlet energy transfer on the picosecond timescale.
• Photochemical isomerization of dithienylethene using UV light and subsequent analysis of fluorescence quenching.
• Modulation experiments using steady-state and modulated light sources to demonstrate transistor-like behavior.

Main Results:

• Efficient singlet-singlet energy transfer was observed among BPEA units with characteristic time scales.
• The BPEA units exhibited high fluorescence quantum yield in the presence of the open-form dithienylethene.
• Photoisomerization to the closed-form dithienylethene resulted in strong quenching of BPEA fluorescence via energy transfer.
• The hexad demonstrated transistor-like modulation of fluorescence intensity by external light signals, exhibiting frequency, amplitude, and phase modulation.

Conclusions:

• The synthesized molecular hexad functions as a light-controlled switch, analogous to a triode vacuum tube or transistor.
• The system allows for the modulation of intense, shorter-wavelength fluorescence using longer-wavelength light.
• This photochemical control mechanism holds promise for applications in fluorescence detection without interference in biomolecular and nanotechnological systems.