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

Abstract

A new coordination polymer, {[Ho(2-stp)(2)(H2O)(2)]center dot 2(4,4'-bipy)(1/2)center dot 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 center dot center dot center dot O interactions to build up 3D network and the free 4,4'-bipyridine molecules occupy the channel of the 3-D network. pi-pi stacking interactions exist between 4,4'-bipy and 2-stp ligands rings, with the centroid-to-centroid distance of 3.847 angstrom 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.