A fluorescent probe of N'-formyl-rhodamine B hydrazide: structure and spectral properties of protonation behaviour.

The title compound is an "off-on" rhodamine probe. It exhibits strong pH dependence and responds to protons. The optimized geometries and energies calculation of the protonation were determined at the B3LYP level using DFT. The theoretical results are in good agreement with the single crystal analysis and the spectral results.