A photochromism of spiropyran derivative based reversible colorimetric chemosensor for recognition of common trivalent metal ions (Al, Cr and Fe)

A designed photochromism of spiropyran derivative, 1'-ethy1-3',3'-dimethy1-6-nitrospiro[4',5'-benzoindole-2,2'-chromene] (BI-SP) as a chemosensor has been synthesized successfully. The as-prepared BI-SP as colorimetric sensor is sensitive to common trivalent metal ions (M3+), such as Al3+, Cr3+ and Fe3+. The dye solution is colorless under visible-light irradiation and remains so even upon addition of the Al3+, Cr3+ and Fe3+ metal ions. However, the dye solution originally appears purple-red in the darkness and gradually turned yellow upon addition of the metal ions at room temperature. Moreover, the sensing abilities of the BI-SP toward the metal ions (Al3+, Cr3+ and Fe3+) were also investigated by UV-Vis absorption spectra and Infrared (IR) spectra. The results indicated that BI-SP could be applied as a sensitive and reversible colorimetric sensor for Al3+, Cr3+ and Fe3+.