Colorimetric and fluorimetric sensors for cyanide ion detection from 3,6disubstituted carbazole derivatives
Anchalee Sirikulkajorn*, Krittasart Singhapha, Sasiwimol Khamoad
Department of Chemistry, Research Center for Academic Excellence in Petroleum, Petrochemical
and Advanced Materials, Faculty of Science, Naresuan University, Muang District, Phitsanulok
*e-mail: [email protected]
Two compounds of 3,6-disubstituted carbazole which are 3-nitro-6-bromocarbazole
(NBC) and 3,6-dicyanocarbazole (DCC) were synthesized. NBC is able to be used as a
colorimetric sensor for anion detection by a distinct color change from light yellow to red
while DCC is a fluorogenic sensor for anion detection by a switch “on” fluorescence
emission. The anion sensing abilities of both sensors were studied by a naked-eye
observation, including UV-Vis, fluorescence and 1H-NMR techniques. Results from the
naked-eye experiments revealed that a selective detection for cyanide ion by NBC and DCC
was obtained in the appropriated solvent system of DMSO:MeOH (1:1). The color of NBC
solution was changed from pale yellow to dark yellow in this system. The luminescent of
DCC was turned on the blue brightness. The lowest concentration in cyanide detection by
the naked-eye observation are 4x10-5 M and 5x10-4 M for NBC in dichloromethane and for
DCC in DMSO:MeOH (1:1), respectively. A deprotonation at NH – carbazole by strong base
anions (OH-, CN- and F-) to induce ICT mechanism was proposed from the 1H-NMR titration
results.
Keywords: Colorimetric sensor; Fluorimetric sensor; Cyanide ion detection, Carbazole derivatives