Novel Anthracene-Appended Calix[4]triazacrown-5 as an Effective Fluorescence Probe for Co2+ and Hazardous Cr2O72− Ions

A new calix[4]triazacrown-5–derived fluorescence chemosensor (AntUr-AzClx) at cone conformation was synthesized to afford an effective fluorescent probe, which enables an enhancement in the fluorescence intensity specifically in the presence of Co²⁺ metal ions as well as a turnoff response for hazardous dichromate anions. ¹H-NMR, ¹³C-NMR, ESI-MS, and elemental analysis techniques were used to characterize the structure of the anthracene-appended calix[4]triazacrown-5 (AntUr-AzClx). The metal ion–binding ability of AntUr-AzClx was evaluated against Co²⁺, Ba²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ ions. On the basis of various metal ion recognition phenomena, AntUr-AzClx exhibited outstanding selectivity for only the Co²⁺ ion among other metal ions. Also, the calix[4]triazacrown-5–derived fluorescence chemosensor showed high sensitivity towards the Co²⁺ ion with a very low limit of detection (LOD) 0.142 μmol L⁻¹. In addition, anion binding abilities of AntUr-AzClx against various anions such Cr₂O₇²⁻, HCO₃⁻, CO₃²⁻, NO₃⁻, SO₃²⁻, SO₄²⁻, N₃⁻, F⁻, and I⁻ demonstrated that AntUr-AzClx enables selective and highly sensitive detection of the Cr₂O₇²⁻ anion with an excellent LOD of 4.182 nmol L⁻¹ in DMF/PBS (1/1, v/v; pH: 7.05). Furthermore, the calix[4]triazacrown-5–derived fluorescence chemosensor displayed a significant sensing behavior to detect the presence of dichromate anions even in real samples.