7',7''-{1,4-Phenylenedi(methylene)bis(5-chloro-1,3,3-trimethyl-1,3-dihydrospiro[indole-2,3'-pyrano[3,3-f] quinolinium])} diiodide – a novel indoline series symmetrically charged photochromic bisspiropyran

A bisspiropyran fluorescent probe for the selective and rapid detection of cyanide anion in liqueurs

“…32,33 Thus, by doubling the substituted electron-withdrawing group, bisspiropyrans accelerate the reaction and increase the lifetime of the open form. 34,35 Filley et al 36 have been proved that bisspiropyrans performed stronger binding ability towards metal ions than monospiropyrans. Thus, bisspiropyran derivatives probably have a better photoluminescence property and may be more suitable fluorescence probes for CN À detection.…”