Donor-Acceptor-Donor Triads with Flexible Spacers: Deciphering Complex Photophysics for Targeted Materials Design

Area of Science:

• Photochemistry and Materials Science
• Supramolecular Chemistry
• Spectroscopy

Background:

• Donor-acceptor-donor (DAD) triads are crucial molecular building blocks.
• Their photophysical properties are sensitive to molecular structure and environment.
• Understanding stimuli-responsive fluorescence is key for advanced materials.

Purpose of the Study:

• To investigate the photokinetics of DAD triads with varying flexible spacer lengths (n=4-10).
• To elucidate the influence of spacer length on charge-transfer (CT) states and emission.
• To correlate photophysical behavior with stimuli-responsive fluorescence switching in solid-state materials.

Main Methods:

• Steady-state and transient fluorescence spectroscopy.
• Investigation across liquid solutions, solid solutions, and crystalline states.
• Computational studies to complement experimental observations.

Main Results:

• Short spacers (n=4) in liquid solution show dynamic CT states and exciplex emission, competing with electron transfer (eT).
• Solid solutions form fluorescent CT static complexes for all spacer lengths upon freezing.
• Spacer length dictates stimuli-responsive fluorescence: on/off switching (n>4) or color change (n=4) in films.

Conclusions:

• Spacer length critically controls photophysical pathways and emission properties in DAD triads.
• The study provides a holistic understanding of stimuli-responsive fluorescence switching in DAD triad films.
• Fundamental photophysical insights can be directly applied to materials science for tunable optical properties.