Syntheses and crystal structures of 1D tubular chains and 2D polycatenanes built from the asymmetric 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene ligand with metal salts

Abstract

Reactions of a new asymmetric ligand, 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene (IIMB), with various metal [Cd(II), Mn(II), Zn(II)] salts led to the formation of molecular, one- (1D) and two-dimensional (2D) architectures [Cd(IIMB)₂(H₂O)(SO₄)]·7.5H₂O 1, [Cd(IIMB)₂Cl₂]·H₂O 2, [Cd(IIMB)₄(H₂O)₂](NO₃)₂·5H₂O 3, [Cd(IIMB)(OAc)₂]·H₂O 4, [Mn(IIMB)₂(SO₄)(H₂O)]·8.2H₂O 5, [Mn(IIMB)₄(H₂O)₂]Cl₂·5H₂O 6 and [Zn(IIMB)₂]₄(NO₃)₈·13.5H₂O 7. All the structures were established by single-crystal X-ray diffraction analysis. Both compounds 1 and 5 with sulfate anion are 2D polycatenanes formed by the interlocking of 1D double-stranded chains, while 2 and 4 with chloride and acetate anions are 1D chains. The results provide nice examples of topologies of metal-organic frameworks controlled by the counter anions. Interestingly, 3 and 6 are discrete molecular complexes with monometallic cores and form 2D networks through strong intermolecular hydrogen bonds. Complex 7, obtained under the same conditions as 3, is a 1D tubular chain. The structural difference between 3 and 7 suggests the metal ions also have a significant effect on the construction of supramolecular architectures. Furthermore, the photoluminescence properties of these compounds were investigated in the solid state at room temperature.