New binuclear Hg(II)-2,3,5,6-tetrakis-(2-pyridyl)pyrazine complexes: Synthesis, characterization, luminescence study and crystal structure determination

چکیده مقاله

The reaction of HgBr₂ and Hg(SCN)₂ with 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) (referred hereafter as tppz) in 2:1 M ratio in mixture of chloroform/methanol/DMSO at 45 °C afforded binuclear complexes [Hg₂(μ-tppz)Br₄] (1) and [Hg₂(μ-tppz)(SCN)₄] (2), respectively, where the tppz act as a bis(tridentate) bridging ligand between identical Hg(II) metal centers. The complexes have been characterized by elemental analyses, FT-IR, ¹HNMR, ¹³CNMR, UV–Vis and luminescence studies. The crystal structures of both complexes have been determined by single crystal X-ray analyses. The luminescence intensity of the free tppz ligand is very weak and the emission of complexes have quenched in comparison with the tppz free ligand. According to the crystal structure determination complexes 1 and 2 have τ₅ value of 0.091 and 0.27, which can be described as slightly distorted square pyramidal and distorted square pyramid geometries, respectively. There are C–H⋯Br hydrogen bonding and C–H⋯π interactions in 1 and C–H⋯N and C–H⋯S hydrogen bonding interactions in 2 which can be responsible for the formation of the supramolecular structure. © 2019 Elsevier B.V.