One-dimensional mercury(II) halide coordination polymers of 3,6-bis (2-pyridyl)-1,2,4,5-tetrazine ligand: Synthesis, crystal structure, spectroscopic and DFT studies

Three new coordination polymers, [Hg(mu-bptz)X-2](n) (X=Cl (1), Br (2)) and [Hg-2(mu-bptz)(mu-I)(2)I-2](n) (3) (bptz=3,6-bis(2-pyridyl)-1,2,4,5-tetrazine) were synthesized. X-ray structural analysis indicated that compounds 1 and 2 are composed of one-dimensional (1D) linear chains while the compound 3 has 1D stair-stepped structure. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that compound 1 and 2 are direct band gap semiconductors; however, compound 3 is an indirect semiconductor. The linear optical properties of the compounds are also calculated by DFT method. According to the DFT calculations, the observed emission band of the compounds in solid state is due to electron transfer from an excited bptz-pi* state (CBs) to the top of VBs. H-1 NMR spectra of the compounds indicate that, in solution phase, the compounds don't decompose completely. Thermal stability of the compounds is studied using TG, DTA methods. (C) 2015 Elsevier Inc. All rights reserved.