Dicarboxylate-controlled three Zn(II) coordination polymers incorporating flexible 1,2-bis(imidazol-1′-yl)ethane ligand: Syntheses, structures, thermal stabilities and photoluminescent properties

Three mixed-ligand Zn(II) coordination polymers (CPs) of the formula {[Zn2(bime)2(adip)2]⋅(H2O)5}n (1), {[Zn(bime)(ipa)]⋅(H2O)3}n (2), {[Zn(bime)(tpa)]⋅(H2O)⋅(CH3OH)}n (3) (bime = 1,2-bis(imidazol-1′-yl)ethane, H2adip = adipic acid, H2ipa = isophthalic acid and H2tpa = terephthalic acid) were synthesized. All CPs have been characterized by element analysis, powder X-ray diffraction (PXRD), IR and X-ray single-crystal diffraction. Complexes 1 and 2 exhibit similar wavy two-dimensional (2D) sheets with 44-sql topology. Compared to 1, complex 2 contains a larger window owing to the different conformation of bime ligand. In both 1 and 2, we observed 1D water chain filling in the 44-sql net. In 3, the bime acts as a bidentate ligand and the tpa adopts a μ2-η1,η1 coordinated mode which links the Zn(II) ions to form a 2D 63-hcb net. The results suggest that the dicarboxylates play crucial roles in the formation of the different structures. In addition, the thermal stabilities and the photoluminescence properties of them were also investigated.

► Three new zinc(II) coordination polymers were synthesized and characterized.
► Three 2D sheets can be simplified to 44-sql and 63-hcb nets.
► Different dicarboxylates as well as bime with different conformations determine the diverse structures.