Over the past years, metastable-state photoacid has become a useful tool for controlling various proton transfer processes with light. Applications of mPAH in energy conversion, sensor, polymerization, patterning, nanomaterial, fragrance release, molecular machine, photochromic materials, and biomedical areas have been reported by our group and other groups. Previously reported mPAHs were activated by visible light. It is important to activate a mPAH with near IR (NIR) light for biological applications since the tissue penetration window (650-1350 nm) is in the NIR range. In this work, we report a new mPAH, which has an absorption band with a λmax at 556nm and 560nm in methanol and DMSO respectively. The tail of the absorption band extends to the NIR region. The mPAH can be effectively activated by 660 nm in methanol and DMSO. In DMSO, when the reverse reaction is slow, activation with 700 nm light was also observed. The quantum yield of the photoreaction was measured to 0.8%. The photoacidity (pKa) of the mPAH was measured to be 5.8 in methanol, and it was able to protonate a pH indicator reversibly under the light.

NIR-responsive metastable-state photoacid

2019 Spring National Meeting

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