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(mu(4)-tdc)(mu-bmeib)(0.5)](n) (1), [Zn(mu(4)-tdc)(mu-betib)(0.5)](n) (2), [Zn(mu(4)-tdc)(mu-bisopib)(0.5)](n) (3), [Zn(mu(4)-tdc)(mu-pbmeix)(0.5)](n) (4), [Zn(mu(4)-tdc)(mu-pbetix)(0.5)](n) (5), [Zn(mu(4)-tdc)(mu-pbisopix)(0.5)](n) (6), bisopib, pbetix, and pbisopix, where H(2)tdc = 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 4(12).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.