Zinc(II) picolinate-based coordination polymers as luminescent sensors of Fe3+ ions and nitroaromatic compounds

Abstract

The synthesis, structure and photoluminescence properties of the zinc(II) picolinate-based coordination polymers [Zn(H2O)2(L1)] (1) and [Zn(L2)2]·0·.5H2O (2) (L12– = 5-((4-carboxyphenyl)ethynyl)picolinate; L2– = 5-(pyridin-3-ylethynyl)-picolinate) are reported. Both compounds exhibit a ligand-based blue emission under UV irradiation. 1 shows a strong enhancement of the emission intensity with respect to the free ligand with a high quantum yield value of 30 %. This luminescence is quenched by the presence of nitrobenzene or Fe3+ cations without loss of the integrity of the sample. The Stern-Volmer plot yields a value of KSV = 121 M−1, indicating a moderate ability for nitrobenzene sensing (limit of detection, LOD = 5.86·10–4 M). For Fe3+ detection, KSV and LOD values of 812 M−1 and 3.78·10–4 M are respectively obtained. 1 exhibits a strong dependence of the luminescent intensity on pH conditions, preserving its crystal integrity in the 2–12 pH range.