Synthesis, structures and properties of three mercury coordination polymers based on 5-methyltetrazolate ligand

Three new mercury coordination polymers, [HgCl2(Hmtz)]n (1), (2) and [Hg2(mtz)4]n (3), were successfully prepared from HgCl2 and 5-methyltetrazole (Hmtz) and characterized by elemental analysis, thermal analysis, luminescence, theoretical calculation, powder X-ray diffraction and single-crystal X-ray diffraction. The results reveal that 1 and 2 are isomers resulted from different one dimensional (1D) mercury halides chains, and they are all 3D supramolecular structures. Complex 3 possesses a 2-fold interpenetrated diamondoid network with intersecting channels. Time-dependent density functional theory (TDDFT) calculations reveal that the mechanisms of the fluorescence emission are dominantly resulted from the ligand-to-metal charge transfer (LLCT) and partial ligand-to-ligand charge transfer (LLCT) for 1 and 2, but ligand-to-metal charge transfer (LMCT) for 3, which is in good agreement with their different fluorescence spectra and crystal structures. Optical absorption spectra indicate that complexes 1–3 have wide optical band-gaps and can be probably used as wide optical band-gap semiconductor materials.