Two zinc (II) coordination polymers based on aliphatic ether Schiff base: Synthesis, crystal structure, antioxidation and fluorescence

Abstract

The synthesis of two 1D coordination polymers [Zn2L12]n 1 and [Zn2L22]n 2, based on the H2L1 (bis (salicylidene)‐3‐oxapentane‐1,5‐diamine) and the H2L2 (bis (5‐methylsalicylaldehyde)‐3‐oxapentane‐1,5‐diamine) ligands, have been described and characterized by IR, elemental analysis and X‐ray single crystal analyses. In coordination polymer 1, each Zn2+ ion is five‐coordinated by three oxygen atoms and two nitrogen atoms from deprotonated ligand forming a square pyramidal configuration. It is worth noting that phenolic oxygens of the deprotonated H2L1 adapt monodentate and monoatomic bridging coordinated modes resulting in one‐dimensional linear chain structure in which macro rings alternately connect small rings. The coordination polymer 2 is a four‐coordinated one‐dimensional zigzag chain in which geometric structure around the Zn (II) atom can be described as distorted tetrahedron. The antioxidant activity of the coordination polymers 1–2 and the ligands were determined by superoxide and hydroxyl radical scavenging method in vitro. The results demonstrated that the coordination polymers exhibit more effective antioxidant activity than the ligands. Moreover, compared with emissive bands of the free ligands in the solid state and DMF solvent, the photoluminescent transition of the Zn (II) coordination polymer 1–2 may be attributed to ligand‐to‐ligand charge‐transfer regulated by Zn (II) ion.