Selective detection and removal of Hg2+ from aqueous medium by a Ni(II) based selenocyanate–containing coordination polymer through the uncoordinated selenium ends

Abstract

The uncoordinated soft selenium end of the selenocyanato moiety present within a newly synthesized Ni(II) based coordination polymer, [Ni(3-bpd)2(NCSe)2]n (1), (3-bpd is 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene) has been implemented for the purpose of selective naked eye sensing as well as efficient removal of Hg2+ ions from its aqueous solution. The synthesis of [Ni(3-bpd)2(NCSe)2]n has been carried out in suitable conditions and this Ni based coordination polymer has been well-characterized with the help of different analytical techniques like single crystal X-ray diffraction analysis, infrared spectroscopy, elemental analysis, FE-SEM analysis, and EDX analysis. The X-ray diffraction analysis of 1 reveals that there exists two selenocyanato moieties attached to the nearly octahedral Ni(II) centre through its nitrogen ends while the selenium ends remain uncoordinated. The approach for the detection as well as removal of Hg2+ is extremely straight-forward. The affinity of Hg2+ towards soft centres is well known. Therefore Hg2+ ions create bonding interaction with the selenium ends of 1. As a result of this interaction the green colored coordination polymer turns grey. FT-IR spectroscopy justifies this bonding interaction. EDX analysis suggests that Hg : Ni ratio in the grey material is 2 : 1. The sensing property of coordination polymer is highly selective towards Hg2+ because its color remains unchanged in the presence of other metal ions.