Basic-to-acidic reversible pH switching with a merocyanine photoacid

Area of Science:

• Photochemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Merocyanine photoacids are light-sensitive molecules that alter pH.
• Previous merocyanine photoacids were limited to neutral and acidic pH ranges.
• Developing photoacids with broader pH switching capabilities is crucial for various applications.

Purpose of the Study:

• To introduce a new merocyanine photoacid with improved pH switching properties.
• To demonstrate the efficacy of the new photoacid across a wide pH range, including basic conditions.
• To overcome the limitations of existing merocyanine photoacids.

Main Methods:

• Synthesis of a novel merocyanine photoacid derivative.
• Characterization of the photoacid's pKa in the dark (pKa_dark).
• Measurement of pH changes induced by visible light irradiation under various initial pH conditions.

Main Results:

• The new merocyanine photoacid exhibits enhanced solubility and a higher pKa_dark.
• A reversible visible light-induced pH jump of up to 3.5 pH units was achieved.
• Demonstrated the first significant pH drop from a basic environment (pH 8.3) to an acidic one (pH 5.2) using a merocyanine photoacid.

Conclusions:

• The novel merocyanine photoacid offers superior pH switching performance compared to existing compounds.
• This photoacid enables precise pH control over a wider range, including transitioning from basic to acidic conditions.
• The findings open new avenues for merocyanine photoacids in areas requiring dynamic pH modulation.