Phenanthroimidazole and dicyanovinyl-substituted triphenylamine for the selective detection of CN-: DFT calculations and practically applications

A novel CN- selective fluorescent turn-on sensor (TPMN) possessing triphenylamine and phenanthroimidazole as signaling units and dicyanovinyl unit for the binding site was designed and synthesized. TPMN exhibited a drastic change in its emission spectra with about 13-fold fluorescence enhancement when treated with CN-, while other tested anions could not arouse the fluorescence enhancement. The experimental and theoretical calculation results showed that this increase in fluorescence intensity of TPMN in presence of CN- is due to the large decrease in the ICT effect by the addition of CN- ion to beta-carbon of the dicyanovinyl moiety. TPMN could selectively detect CN- with a detection limit of 0.23 mu M among the common anions. The CN--binding mode was well-characterized to be 1:1 by using Job's plot with an association constant of 5.36 (logK(a)). Besides, the possible utilization of TPMN was successively tested in water samples and test kits.