In this project, design and synthesis of N-(1,3-thiazole-2-yl)-pyrazine-2-carboxamide ligand (L) was performed and the product was initially characterized by CHN microanalysis, IR and Mass spectroscopies. While attempt to obtain the suitable single crystal of ligand, three polymorphic moieties (LI, LII, LIII) were achieved that the structures were determined by X-ray diffraction analysis. In the following, the crystal structures of polymorphs were investigated from crystal engineering viewpoint. Investigations showed that the asymmetric unit of three compounds contains two independent molecules of ligand which have different orientations and interactions with each other. The results of Hirshfeld surface analysis, finger print plot and theoretical studies on dimer and tetramer moieties, indicated to the important role of hydrogen bonding and weak π-based interactions in the LI-III crystal structures. Exploring the stability energies related to the species being theoretical studied, emphasized to the role of hydrogen bonding interactions in the stability of polymorphic structures. In the next step, new complexes of mercury(II) halides series and cadmium(II) chloride with ligand (L), [Hg3Cl6(L)2]n (1), [Hg2Br4(L)]n (2), [HgI2(L)]n (3) and [CdCl2(L)]n (4) were synthesized and characterized by melting point (mp), CHN microanalysis and IR spectroscopy. The results of X-ray crystallography analysis of complexes 1 and 2 showed that the change of accompanying anion leading to the different polymeric structures. In this regard, the 2D polymeric chain as a triplet-rail ladder-type in complex 1 and the 1D polymeric chain as a double-rail ladder-type in complex 2 were identified. Moreover, the effect of accompanying anion resulted in the change of coordination sphere of metal center. Structural investigation revealed that CH⋯π and S⋯Cl interactions in complex 1 and amide⋯π, Br⋯S, Br⋯H and Br⋯H interactions in complex 2 are involved in the packing of polymeric structures. |
