||Carbazole based fluorescence chemosensor 23, 1,8-bis(3-phenyl-isoxazolyl)-3,6- di-tert-butyl-9H-carbazole, was prepared and characterized by NMR, MALDI-MS, absorption and emission spectroscopy.|
The sensing properties of 23 toward various metal ions were investigated in CH3CN solution. A highly selective fluorescent turn-off response is observed in the presence of copper (II) among other metal ions, as is observed with the addition of 10 equiv of Li+, Na+, K+, Mg2+, Ca2+, Ba2+, Cd3+, Mn2+, Ni2+, Ag+, Pb2+, Zn2+, Cu2+, Hg2+ ions. The fluorescence intensity is almost not influenced by the addition of other metal ions. A Job’s plot determining the stoichiometry ratio of 23 and Cu2+ in CH3CN indicates a simple one-to-one binding preference. The binding constant for Cu2+ ion with 23 is 2.2 × 104 M-1.
Another carbazole based chemosensor 24 is derived from 23. We found that 24 can bind to six metal ions. Especially with nickel ions and zinc ions, significant color change can be easily observed by naked eyes.