Influence of the counter anion and steric hindrance of pyrazolyl and imidazolyl flexible ligands on the structure of zinc-based coordination polymers

摘要

Treatments of flexible 1,4-bis(3,5-dimethylpyrazolyl)butane (bbd), 1,4-bis(imidazolyl)butane (bib) and 1,4-bis(2-methylimidazolyl)butane (bmib) ligands with zinc salts at room temperature, resulted in the formation of four novel metal-organic coordination architectures: [ZnI_2(μ-bbd)]_n (1), [Zn(NCS)_2(μ-bbd)]_n (2), {[Zn(μ-bib)_2](ClO_4)_2?(Et_2O)_(0.5)?(H_2O)_(0.25)}_n (3) and {[Zn(μ-bmib)_2](ClO_4)_2?(H_2O)_4}_n (4). X-ray crystallographic analyses show different 1D and 3D polymeric structures for compounds 1-4 due to the variation of the counter anions, solvent, steric hindrance and position of donating atoms in the structure of flexible ligands. In 1 and 2, one-dimensional (1D) zig-zag polymeric chains are formed via metal centers and l-bbd ligands. Complex 3 shows a 3-fold interpenetrated 3D architecture with 10~3-ths network topology. In contrast to 3, in the structure of 4 neighboring Zn(II) ions are interconnected by a double-bridging l-bmib ligands to form an infinite 1D polymeric double chain. The conformations of the flexible ligands were analyzed in detail.