Heterobimetallic thiocyanato-bridged coordination polymers based on [Hg(SCN)4]2-: Synthesis, crystal structure, magnetic properties and ESR studies

Three new M/Hg bimetallic thiocyanato-bridged coordination polymers; [Hg(SCN)4Ni(Im)3] ∞ 1, [Hg(SCN)4Mn(Im)2] ∞ 2, and [Hg(SCN)4Cu(Me-Im)2 Hg(SCN)4Cu(Me-Im)4] ∞ 3, (Im=imidazole, Me-Im=N-methyl-imidazole), have been synthesized and characterized by means of elemental analysis, ESR, and single-crystal X-ray. X-ray diffraction analysis reveals that these three complexes all form 3D network structure, and their structures all contain a thiocyanato-bridged Hg...Hg chain (M=Mn, Ni, Cu) in which the metal and mercury centers exhibit different coordination environments. In complex 1, the [Hg(SCN)4]2- anion connects three [Ni(Im)3]2+ using three SCN ligands giving rise to a 3D structure, and in complex 2, four SCN ligands bridge [Hg(SCN)4]2- and [Mn(Im)2]2+ to form a 3D structure. The structure of 3 contains two copper atoms with distinct coordination environment; one is coordinated by four N-methyl-imidazole ligands and two axially elongated SCN groups, and another by four SCN groups (two elongated) and two N-methyl-imidazole ligands. The magnetic property of complex 1 has been investigated. The spin state structure in hetermetallic NiHgNi systems of complex 1 is irregular. The ESR spectra results of complex 3 demonstrate Cu2+ ion lie on octahedral environment. -- Graphical abstract: Three new M/Hg bimetallic thiocyanato-bridged coordination polymers; [Hg(SCN)4Ni(Im)3] ∞ 1, [Hg(SCN)4Mn(Im)2] ∞ 2, and [Hg(SCN)4Cu(Me-Im)2 Hg(SCN)4Cu(Me-Im)4] ∞ 3, (Im=imidazole, Me-Im=N-methyl-imidazole), have been synthesized and characterized by single-crystal X-ray. All coordination polymers possess 3-D structures, and consist of organic base neutral ligands (imidazole and N-methyl-imidazole) and SCN-1 anions. Their structural difference is mainly caused by the role of the organic base and metal ions. The complex 1 shows the irregular spin state structure