Dimeric and polymeric mercury(II) complexes of 1-methyl-1,2,3,4-tetrazole-5-thiol: Synthesis, crystal structure, spectroscopic characterization, and thermal analyses

• Three novel mercury(II) complexes of [Hg(μ3-mmtz)2]n, {[H2en][Hg2(mmtz)4(μ-Br)2]} and {[H2en][Hg2(mmtz)4(μ-I)2]} were obtained and fully characterized.
• The [Hg(μ3-mmtz)2]n complex has a two-dimensional structure.
• The {[H2en][Hg2(mmtz)4(μ-Br)2]} and {[H2en][Hg2(mmtz)4(μ-I)2]} complexes are isostructural centrosymmetric dinuclear.
• Photoluminescence studies show that the three complexes exhibit strong luminescence.

Two-dimensional coordination polymer of [Hg(μ3-mmtz)2]n (1) and centrosymmetric dinuclear complexes of {[H2en][Hg2(mmtz)4(μ-Br)2]} (2) and {[H2en][Hg2(mmtz)4(μ-I)2]} (3) (where Hmmtz is 1-methyl-1,2,3,4-tetrazole-5-thiol and en is ethylene diamine) were synthesized from the reaction of Hmmtz and en with HgCl2, HgBr2 and HgI2, respectively, in CH3OH. Complex 1 was also synthesized from the reaction of Hmmtz and en with HgX2 (X = OAc and SCN) in CH3OH. These three complexes were thoroughly characterized by elemental analysis (CHN), thermal gravimetric analysis (TGA), differential thermal analyses (DTA), infrared, UV–vis, 1H NMR, and luminescence spectroscopy, and their structures were determined by single-crystal X-ray diffraction.