Synthesis, crystal structures, and alcohol vapor adsorption properties of Cd(II) and Cu(II) complexes based on a salen-type Schiff base

A salen-type Schiff base ligand (H4L) was designed and synthesized from the condensation reaction. Four complexes, formulated as {[Cd(H5L+)Cl2(μ2 − Cl)]·2CH3OH}n (1), {[Cd(H4L)Br2]·H2O}n (2), {[Cd2(H4L)2I4]·CH3OH}n (3), and [Cu3(L4-)(μ3 − Ac)2]·CH3OH·H2O (4) were synthesized and characterized by single-crystal X-ray diffraction. Complex 1 exists as a 2D sheet structure and each Cd(II) ion in the complex is six-coordinated with an octahedral geometry. Both complexes 2 and 3 exist as 1D zig-zag structures and each Cd(II) ion in the two complexes is five-coordinated with a trigonal bipyramidal geometry. Complex 4 exists as a centrosymmetric trinuclear structure, in which two Cu(II) ions are five-coordinated with a square pyramidal geometry and the other Cu(II) ion is six-coordinated with an octahedral geometry. The structural differences are attributed to coordination ability of the coordination sites and coordination configurations of the metal ions. Furthermore, alcohol vapor adsorption measurements showed that all the synthesized complexes exhibited good adsorption capacities toward methanol vapor.