A novel selective colorimetric chemosensor for cobalt ions in a near perfect aqueous solution

A novel chemosensor 1 (1 = 2-(N-(2-hydroxybenzyl)-N-((pyridin-2-yl)methyl)amino)-N-(2-hydroxyphenyl)acetamide) was synthesized and characterized. The receptor 1 showed a selective colorimetric sensing ability for cobalt ion by changing color from colorless to pale violet in a near perfect aqueous solution, facilitating naked eye detection of Co3+ through the oxidation of Co2+ to Co3+. This phenomenon could be possibly explained by ligand-to-metal charge-transfer. Moreover, the detection limit (1.8 μM) of 1-Co complex is comparable to the environmental protection agency (EPA) guideline (1.7 μM) in drinking water. Practically, 1 also functioned when supported by silica, indicating that receptor 1 had the potential for working as optical solid sensors.