Five Cd(II) coordination polymers based on 2,3′,5,5′-biphenyltetracarboxylic acid and N-donor coligands: syntheses, structures and fluorescent properties

Five Cd(II) coordination polymers, {[Cd-2(Hbptc)(2)(H2O)(2)]center dot(1,3-H(2)bip)}(n) (1), [Cd-2(bptc)(1,4-bib) (H2O)(2)](n) (2), {[Cd-2(bptc)(bix)(H2O)(2)]center dot 3H(2)O}(n) (3), [Cd(H(2)bptc)(bimb)(H2O)](n) (4) and [Cd-2(bptc)(tib)(H2O)](n) (5), where H(4)bptc = 2,3',5,5'-biphenyltetracarboxylic acid, 1,3-bip = 1,3-bis(imidazole) propane, 1,4-bib = 1,4-bis(imidazole) butane, bix = 1,4-bis(imidazol-1-ylmethyl) benzene, bimb = 4,4'-bis(imidazol-1-ylmethyl) biphenyl and tib = 1,3,5-tris(imidazol-1-yl) benzene, have been synthesized using Cd(II) acetate with H4bptc and different bis(imidazole) ligands under hydrothermal conditions. Their structures have been characterized using elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD) analysis. Complex 1 displays a (3,6)-connected CdI2 topology, which further forms a 3D supramolecular framework by O-H center dot center dot center dot O hydrogen bonding interactions. Complex 2 features a 3D network with a (4,5,7)-connected (3.4(3).5(2))(3.4(3).5(2).6(3).7)(3.4(6).5(4).6(8).7(2)) topology. Complex 3 exhibits a 3D framework with a (3,4,5)-connected (5.6.7)(4.5(2).6.7.8)(4.5(2).6(2).7(3).8(2)) topology. Complex 4 has a 2-fold interpenetrated (4,4) net. Complex 5 possesses a 3D self-penetrating network with two dia nets. The results show that H(4)bptc can act as a versatile building block for the construction of various metal-organic frameworks (MOFs). Moreover, the fluorescent properties of 1-5 in the solid state have been investigated.