A selective colorimetric sensor for Cu2 + in aqueous solution

We synthesized a novel Schiff-based receptor 1, and investigated its binding properties toward various metal ions. Receptor 1 showed a dramatic color change from colorless to red which could easily be detected by the naked-eye upon binding with Cu2 +. The association constant for 1 · Cu2 + in DMSO/H2O (v/v, 1:9) was calculated to be 1.98 × 108 M− 1. With the addition of Na2EDTA to a mixture of receptor 1 and Cu2 +, the solution changed back to its original colorless appearance instantly.