Coordination Polymers with Varied Metal Centers and Flexible Tripodal Ligand 1,3,5-Tris(imidazol-1-yimethyl)benzene: Synthesis, Structure, and Reversible Anion Exchange Property

Seven new coordination polymers ([Cu-3(tib)(4)](NO3)(6) center dot 4.94H(2)O}(n) (1), {[Cu-2(tib)(2)(SO4)(2)}center dot 2EtOH center dot 2H(2)O}(n) (2), [Cu(tib)Cl-2](n) (3), {[Cd(tib)(2)](NO3)(2)center dot 4H(2)O](n) (4), {[Cd(tib)(H2O)(2)(SO4)]center dot EtOH center dot H2O}(n) (5) {[Co(tib)(H2O)(2)(SO4)]center dot EtOH center dot H2O}(n) (6), and {[Ni(tib)(H2O)(2)(SO4)]center dot EtOH-H2O}(n) (7) (EtOH = ethanol) were prepared by reactions of flexible tripodal ligand 1,3,5-tris(imidazol-1-ylmethyl)benzene (tib) with the corresponding metal salts. Their structures were determined by X-ray crystallography. The different structures of 1-3 as well as 4 and 5 indicate that the counteranions play an important role in the construction of coordination polymers. The distinct structures of Cu(II) and Cd(II) complexes with die same counteranion demonstrate that the metal centers with different coordination geometry have a significant influence on the structures, The same 1D chain structure of 5-7 indicated that the metal centers with the same octahedral coordination geometry do not affect the structure of the complexes. On the other hand, ligand tib acts as a three-connecting linker to connect three M(II) centers with different conformations. In 1, two different conformations (cis, trans, trans-, and trans-) of tib coexist. In 2-4, tib adopts the cis, trans, trans-con formation, while in the case of 5-7, tib has the cis, cis, cis-conformation. The results attest that the flexible tripodal ligand tib can adopt different conformations to form complexes with varied structures. Furthermore, the reversible anion exchange properties of 1 and 4 were studied.