The off-on fluorescent chemosensor based on the bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)methane for detection of Cd2+ and Hg2+ ions was obtained and its metal ion sensing properties were investigated. The bis(dipyrrin) exhibited remarkably fluorescence enhancement (150- and 40-fold) to Cd2+ and Hg2+ ions, respectively, with significant color change on the background of other metal ions in propanol-1/cyclohexane (1:30) binary mixture. Consequently, it can be used as a naked eye indicator with an obvious color change from yellow-orange to orange-green color upon the addition of Cd2+ and Hg2+. The fluorescent response mechanism of bis(dipyrrin) to Cd2+ and Hg2+ was based on the fluorescence enhancement effect upon complexation (CHEF) due to formation of a metalligand (2:2) complex [M2L2]. The detection limit of Cd2+ and Hg2+ ions was 2 x 10(9) and 1.7 x 10(8) M ions, respectively.
