Fluorescent probes for Al(III) and Cr(III) based on a photochromic diarylethene bearing a fluorescent rhodamine unit

A sensitive and selective “turn-on” fluorescent probe (compound 1O) was prepared by combining a photochromic diarylethene with a fluorescent rhodamine unit. This compound displays a favorable photochromism on alternating irradiation with UV/Vis light. Upon addition of Al(III) or Cr(III) to the probe, its color changes from colorless to pink, and its fluorescence is markedly enhanced. The probe displays excellent sensitivity and selectivity for these ions. Another probe (compound 1C) was also prepared and is found to undergo a color change from pea green to pink after binding Al(III) or 30(III). Sensitivities were studied, and competition experiments with various other metal ion revealed that compound 1C possesses good and selective fluorescence response to Al(III) and Cr(III).