Three Cationic, Nonporous CuI-Coordination Polymers: Structural Investigation and Vapor Iodine Capture

Three cationic nonporous copper(I) coordination polymers containing bis-pyrazolyl flexible ligands have been prepared and characterized, namely, {[Cu(mu-bdb)(1.5)](PF6)}(n) (1), {[Cu(mu-bpb)(2)](PF6)}(n) (2), and {[Cu(mu-bpmb)(2)](PF6)}(n) (3) (bdb = 1,4-bis(3,5-dimethylpyrazolyl) methyl)benzene; bpb = 1,4-bis(pyrazolyl)butane; bpmb = 1,4-bis(pyrazolypmethyl)benzene). All compounds were characterized by infrared, powder X-ray diffraction, elemental and thermal analyses, and single crystal X-ray diffraction. Compound 1, with methyl-substituted pyrazolyl ligand, forms a chain of alternating rings and ribbons in which the copper(I) centers are three coordinated in distorted trigonal planar geometry. In compounds 2 and 3 copper(I) atoms adopt distorted tetrahedral geometries giving two-dimensional sheet structures with 4(4)-sql topology. Interestingly, iodine sorption experiments show that colorless crystals of 2 and 3 remain unchanged in the presence of iodine vapors, while the three coordinated compound 1 immediately absorbs iodine and turns dark. Anion exchange behavior of compounds 1 and 2 was also investigated both in solution and in the solid state.