Hydrothermal synthesis, crystal structure and Photoluminescent properties; 3D Holmium(III) coordination polymer

Abstract

A new coordination polymer, {[Ho(2-stp)2(H2O)2]·2(4,4′-bipy)1/2·5(H2O)}n, 1, (2-stp=2-sulfoterephthalate anion and 4,4′-bipy=4,4′-bipyridine) has been synthesized by hydrothermal method and characterized by elemental analysis, IR, single-crystal X-ray diffraction. The Ho(III) atoms are bridged by two 2-stp ligands to form infinite chains which are associated through O–H⋯O interactions to build up 3D network and the free 4,4′-bipyridine molecules occupy the channel of the 3-D network. π–π stacking interactions exist between 4,4′-bipy and 2-stp ligands rings, with the centroid-to-centroid distance of 3.847Å. Additionally, solid state photoluminescence properties of 1 at room temperature have been investigated. Under the excitation of UV light, the compound 1 exhibited characteristic emissions of Ho(III) ion in the visible and the near-infrared (NIR) regions.