Three coordination polymers as a multi-responsive luminescent probe for the detection of Fe3+, Cr2O72- and antibiotic in aqueous media

Three coordination polymers (CPs), namely {[Co(L)(dpa)].H2O}n (1), {[Zn(L)2(dpb)]}n (2) and {[Zn(L)(dpe)]}n (3), have been assembled through a dual-ligand strategy of a semi-rigid dicarboxylic acid (H2L = 1,4-bis(4phenoxy)benzenedicarboxylic acid) with the help of different N-donor co-ligands (dpa = di(pyridin-4-yl)amine, dpb = 1,4-di(pyridin-4-yl)benzene), dpe = trans-1,2-di(4-pyridyl)ethylene). Single crystal X-ray diffraction analyses reveals that compound 1 is a 4-fold interpenetrating 2D sql network and compound 2 is a 2-fold interpenetrating 2D sql network, although the final structures are different because of various inter-layer stacking modes. Compound 3 is a 8-fold interpenetrating 3D dia framework containing an octahedral cage. A photoluminescence investigation shows that compounds 2 and 3 exhibit strong fluorescence originating from the intraligand charge transfer transitions. Benefiting from its chemical stability and luminescent properties, compound 2 possesses multi-functional fluorescent responses toward the Fe3+ ion, the Cr2O72- ion and the NZF antibiotic in aqueous medium. The KSV values of compound 2 are 4.68 x 104 M-1 for the Fe3+ ion, 7.23 x 104 M-1 for the Cr2O72- anion, and 1.03 x 104 M-1 for the NZF antibiotic. Additionally, the possible mechanism for the luminescence quenching has been investigated.