Fluorescent probe with high quantum efficiency, exhibiting single exponential decay kinetics. The radiative fluorescence lifetime is almost constant and independent on molecular surroundings allowing this probe to be utilized in a range of microsurroundings with exciting radiation at a constant wavelength (in the blue spectral range). Its fluorescence emission demonstrates a large solvatochromic shift which changes with solvent polarity. For example, the maximum shifts from 435 nm in low polarity n-heptane to 492 nm in high polarity acetonitrile. This product is only sparingly soluble in water