Dipicolylamine Derivatives Bearing Pyrene and Anthracene as Molecular Probes for Cu²⁺ and H₂S

Two dipicolylamine (DPA) derivatives with the pyrene and anthracene groups, 1-(pyren-1-yl)-N, N-bis-(pyridine-2-ylmethyl)benzylamine (L1) and 1-(anthracen-9-yl)-N, N-bis-(pyridine-2-ylmethyl)benzylamine (L2) were synthesized, characterized, and their affinitive properties for metal ions were studied. The mass spectroscopy and Job's plots showed that L1 and L2 reacted with Cu²⁺ and formed complexes [Cu(L1)(solvent)]²⁺ (L1-Cu²⁺) and [Cu(L2)(solvent)]²⁺ (L2-Cu²⁺), respectively. Both L1 and L2 were fluorescent probes recognizing Cu²⁺ via the emission quenching and further detecting H₂S via the emission revival. The probes L1 and L2 displayed high sensitivity and selectivity as well as rapid response in the detection of Cu²⁺ and H₂S. The limit of detection (LOD) values of L1 and L2 for Cu²⁺ were 16 nM and 17 nM, respectively, and those of complexes L1-Cu²⁺ and L2-Cu²⁺ for S^2- were 18 nM and 19 nM, respectively. The response time of L1 and L2 was within 10 s for Cu²⁺ and 20 s for S^2-. Furthermore, L1 and L2 were applicable to the detection of Cu²⁺ in actual water samples with good recovery. The efficient response of L1 and L2 to Cu²⁺ and S^2- benefited from the strong electron transfer ability of the benzyl group between the DPA and the pyrene (or anthrence) groups. It showed that the judicious combination of the linker, the dipicolylamine and the chromophore group could offer molecular systems that were promising candidates for the detection of both metal ions and anions.