Two Key Descriptors for Designing Second Near-Infrared Dyes and Experimental Validation

Area of Science:

• Organic Chemistry
• Materials Science
• Biomedical Imaging

Background:

• Second near-infrared (NIR-II) optical imaging offers superior contrast for diagnostics and surgery.
• Efficient design strategies for NIR-II organic dyes are lacking due to synthesis challenges, hindering bioprobe development.

Purpose of the Study:

• To establish a general strategy for efficiently designing NIR-II organic molecules.
• To identify key descriptors for predicting NIR-II emission spectra.
• To validate theoretical predictions through experimental synthesis and biological imaging.

Main Methods:

• Theoretical calculations were performed on 62 multiaryl-pyrrole (MAP) systems.
• Two descriptors, ΔEgs (ground state energy gap) and μgs (ground state dipole moment), were identified and correlated with spectral properties.
• Experimental validation involved synthesizing ten MAPs and performing in vivo biological imaging.

Main Results:

• Adjusting substituents on MAPs enabled spectral red-shifting into the NIR-II region.
• ΔEgs and μgs were found to be reliable predictors of NIR-II emission under specific conditions (ΔEgs ≤ 2.5 eV, μgs ≤ 22.55 D).
• In vivo imaging of MAP23-BBT demonstrated high-resolution deep tissue angiography in the NIR-II window.

Conclusions:

• A predictive framework for designing NIR-II dyes based on ΔEgs and μgs was established.
• The identified descriptors show broad applicability beyond MAP systems to other donor-acceptor-donor NIR-II dyes.
• This work facilitates the efficient development of novel NIR-II bioprobes for advanced biomedical applications.