Exploring Multiexciton Generation in an Asymmetric Aza-BODIPY Dimer

Area of Science:

• Photophysics
• Organic Chemistry
• Quantum Dynamics

Background:

• Aza-BODIPY dyes are important chromophores.
• Understanding photophysical processes in dimers is crucial for applications.
• Singlet fission (SF) is a promising pathway for enhanced solar energy conversion.

Purpose of the Study:

• Investigate the photophysics of the aza-BODIPY dimer D[1,3].
• Determine the feasibility and mechanism of singlet fission in this dimer.
• Explore alternative pathways for triplet-state generation.

Main Methods:

• Multireference electronic structure calculations.
• Quantum nuclear dynamics simulations.
• Spin-orbit coupling calculations.

Main Results:

• The aza-BODIPY dimer D[1,3] exhibits strong electronic couplings and weakly endoergic singlet fission energetics.
• Quantum dynamics simulations reveal rapid formation of a superexchange-like state within 50 fs.
• Singlet fission is inefficient due to limited multiexcitonic character; charge-transfer manifold becomes populated.
• Spin-orbit charge-transfer intersystem crossing (SOCT-ISC) is identified as an effective pathway for triplet generation.

Conclusions:

• Singlet fission is not the primary pathway for triplet generation in the D[1,3] aza-BODIPY dimer.
• The SOCT-ISC mechanism provides a more efficient route for generating triplet states.
• These findings offer insights into designing novel photophysical processes for optoelectronic applications.