Dual Colorimetric/Fluorometric Double-Throw pH-Switches: The Dimroth Rearrangement of N,9-Diaryl 8-Azaadenines.

A library of 12N,9-Diaryl 2-methyl-8-azaadenine (DAMA) compounds was designed and constructed through an aryl-pairing combination strategy for identifying a nucleobase-containing molecular switch that functions by the pH-regulated Dimroth rearrangement. By utilizing 2D thin-layer chromatography/mass spectrometry (2D-TLC-MS), the DAMA compounds were easily screened to identify which compounds could be used as molecular switches. The pH-switching ability of the DAMA was achieved by incorporating the acridine group as the key structural unit, as well as dual-modal colorimetric/fluorometric on/off properties as the probe functions. The real-time tracing of the switching process clearly indicated that the paired aromatics on both terminals of the DAMA molecule play a key role in tuning the switching kinetics.