Syntheses and crystal structures of metal complexes with 2,2 '-biimidazole-like ligand and chloride: Investigation of X-H center dot center dot center dot Cl (X = N, O, and C) hydrogen bonding and Cl-pi (imidazolyl) interactions

摘要

Six complexes containing the 2,2 '-biimidazole-like ligand and chloride, namely, trans-[Ni(H(2)biim)(2)(H2O)(2)]Cl-2 (1), trans-[Co-1.5(H(2)biim)(3)(H2O)(3)]Cl-3 (2), [Zn(H(2)biim)(2)Cl]Cl (3), [Ni-2(H(2)bbim)(4)(bbim)]Cl-2 (4), [Co(H(2)bbim)(3)]Cl-2 center dot 2H2O (5), and [Zn-2(Hbbim)(2)(bbim)(0.5)Cl] (6) (where H(2)biim = 2,2 '-biimidazole, H(2)bbim = 2,2 '-bibenzimidazole) have been synthesized by the reactions of the H(2)biim or H(2)bbim ligand with the metal chloride salts. The structures, of the complexes were determined by singlecrystal X-ray diffraction analyses, and the results revealed that the distances of N center dot center dot center dot Cl varied from 3.10 to 3.29 angstrom and the angles of N-H center dot center dot center dot Cl varied from 148 to 169 degrees, O center dot center dot center dot Cl varied from 3.09 to 3.16 angstrom, O-H center dot center dot center dot Cl varied from 151 to 178 degrees C center dot center dot center dot Cl varied from 3.49 to 3.69 angstrom, and C-H center dot center dot center dot Cl varied from 122 to 167 degrees. The chloride may act as a multi hydrogen bonded acceptor varying from 3 to 6. resulting in an important collective contribution to cohesion. The data observed in this study seem to suggest that a variety of X-H center dot center dot center dot Cl (X = N, O, and C) synthons identified here play a crucial role in the formation and further stabilization of supramolecular architecture, for instance, to link the discrete. (0D) or low-dimensional (1D) entities into high-dimensional frameworks. In particular, the coplanar [(H2O)(2)Cl-2](2-) guests are encapsulated in the cavities formed by four [Co(H(2)bbim)(3)](2+) cations and stabilized via accepting 6-fold hydrogen bonds from three H(2)bbim ligands in 5. The distance hetween the chloride anion and the imidazolyl ring (Cl center dot center dot center dot centroid, 3.30 angstrom and 80 degrees) demonstrates the possible existence of Cl center dot center dot center dot pi (imidazolyl) charge-assisted interactions because the coordination of a positively charged Co(II) ion greatly enhances the electron-deficient character of the imidazolyl ring and provides sufficient polarization to produce an anion-pi charge-assisted interaction.