RUI: pyrazoloindazoles as long wavelength chromophores and emitters

The National Science Foundation's Division of Chemistry awarded $365,000 under the Mathematical and Physical Sciences program (CFDA 47.049) to Macalester College, with an award date of June 15, 2025 and completion target of May 31, 2028. The project, led by Professor Dennis Cao, focuses on the development and characterization of pyrazoloindazole organic dye compounds that interact with near-infrared (NIR) light. The primary deliverables include the synthesis and photophysical characterization of curated libraries of modified pyrazoloindazoles, identification of design principles for achieving compounds with enhanced absorption and emission wavelengths exceeding 700 nanometers, and investigation of the redox activity of the pyrazoloindazole scaffold to evaluate radical ion states with narrow energy gap characteristics.

The research will generate applications toward solar energy harvesting outside the visible light spectrum and biomedical imaging agents for deep tissue visualization. The project emphasizes workforce development through hands-on training of undergraduate researchers in laboratory courses and full-time summer research positions, as well as mentorship of visiting graduate students in research program management within an undergraduate institution setting. No sub-awards are planned for this project grant.

Abstract

With the support of the chemical mechanism, function, and properties program of the division of chemistry, professor dennis CAO of the chemistry department at macalester college is developing a class of organic DYE compounds that interact with near-infrared light. The goal of this research is to unlock design principles toward organic dyes that can harvest solar energy outside the visible region of light and/or serve as imaging agents deep within living tissue. The research activities in synthesis and photophysical characterization will be conducted by undergraduate researchers both in laboratory courses and in full-time summer positions, providing excellent training and workforce development. The CAO lab will also host visiting graduate student researchers and provide them with first-hand experience of running a research program and mentoring in the context of an undergraduate institution. Computational investigations suggest that the pyrazoloindazole scaffold has remarkable potential as a near-infrared (NIR) chromophore, with an electronic structure that is 1) sensitive to structural modifications for varying the homo-lumo GAP and 2) likely to be a NIR light emitter. Curated libraries of modified pyrazoloindazoles will be synthesized and investigated to identify design rules for achieving compounds with enhanced absorption and/or emission maxima longer than 700 NM. The project team additionally will investigate the redox activity of the pyrazoloindazole scaffold in anticipation of achieving radical ION states that exhibit narrow energy GAP characteristics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.