A Series of Zinc(II) 3D → 3D Interpenetrated Coordination Polymers Based On Thiophene-2,5-dicarboxylate and Bis(Imidazole) Derivative Linkers

Six
coordination polymers of Zn­(II) ions and three organic linkers
namely, [Zn­(μ4-tdc)­(μ-bmeib)0.5]n (1), [Zn­(μ4-tdc)­(μ-betib)0.5]n (2), [Zn­(μ4-tdc)­(μ-bisopib)0.5]n (3), [Zn­(μ4-tdc)­(μ-pbmeix)0.5]n (4), [Zn­(μ4-tdc)­(μ-pbetix)0.5]n (5), [Zn­(μ4-tdc)­(μ-pbisopix)0.5]n (6), bisopib, pbetix, and pbisopix, where H2tdc = thiophene-2,5-dicarboxylic acid, bmeib = 1,4-bis­(2-methyl-1H-imidazol-1-yl)­butane, betib = 1,4-bis­(2-ethyl-1H-imidazol-1-yl)­butane, bisopib = 1,4-bis­(2-isopropyl-1H-imidazol-1-yl)­butane, pbmeix = 1,4-bis­((2-methyl-1H-imidazol-1-yl)­methyl)­benzene,
pbetix = 1,4-bis­((2-ethyl-1H-imidazol-1-yl)­methyl)­benzene,
pbisopix = 1,4-bis­((2-isopropyl-1H-imidazol-1-yl)­methyl)­benzene,
have been synthesized and structurally characterized by elemental
analysis, IR spectra, NMR spectra and single-crystal and powder X-ray
diffractions. Compounds 1–6 are isostructural and display a
3D cubic structure with 2-fold interpenetrated nets. Two crystallographically
independent Zn­(II) ions are bridged by four different thiopehene-2,5-dicarboxlylate
linkers adopting a bis­(monodentate) coordination mode to form a paddle-wheel
unit forming two-dimensional layers. These 2D layers containing paddle-wheel
unit are further pillared by bridging bis­(imidazole) derivative linkers
forming a 3D framework. Moreover, topological analyses show that two
3D frameworks are interlocked with each other to give a 2-fold interpenetrating
pcu net with 412.63 topology. Interestingly,
compound 3 is a 2-fold heterointerpenetrating 2­(1 + 1)
three-dimensional (3D) framework. In addition, photoluminescence properties,
thermal stabilities and Cu­(II) ion exchange properties of the compounds
were also investigated.