Investigation of onno type Schiff bases as a fluorescence chemosensor for zinc analysis

Fluorescent chemosensors have been developed to be a useful tool to determine the enviromentally and biologically important species such as metal ions. Zinc ion (Zn2+) has attracted a great deal of attention because of the biological significance of this metal. In this regard, N,N'-bis(salicylidene)-2,2'-dimethyl-1,3-propanediamine (LDMH2) and the reduced derivative of this Schiff base bis-N,N'-(2-hydroxybenzyl)-2,2'-dimethyl-1,3-propanediamine (LDMHH2) have been synthesized and used as fluorescent chemosensor for the detection of zinc ions. While LDMH2-Zn complex displayed a high fluorescence emission, LDMHH2-Zn showed no fluorescence responce. Moreover, other common alkali, alkaline earth and transition metal ions exhibited no interference on the selectivity of Zn2+. In other words, this chemosensor could distinguish clearly Zn2+ from other ions. Optimization studies were then carried out on LDMH2-Zn complex in order to increase the fluorescence intensity of this molecule. According to obtained results, the highest fluorescence intensity was achieved at neutral pH, 10-4 M ligand concentration and in ethanol–water mixture. Finally, the calibration curve was created and the method was tested with a Certified Reference Material (CRM).