Structural Variations Influenced by Ligand Conformation and Counteranions in Copper(II) Complexes with Flexible Bis-Triazole Ligand

Using a flexible bis-triazole ligand 1,4-bis(triazol-1-ylmethyl)benzene (L), four new copper(II) compounds {[Cu(trans-L)(cis-L)₂(H₂O)₂](CF₃SO₃)₂·4H₂O}_n (1), {[Cu(cis-L)₂(H₂O)₂](CF₃SO₃)₂·2H₂O}_n (2), {[Cu(trans-L)₂]Cl₂}_n (3), and {[Cu(trans-L)(cis-L)](BF₄)₂}_n (4) have been isolated. Conformations of L in 1−4 can be tuned as a result of changing the anion or metal/ligand ratio in the reaction system, which ultimately form a series of novel framework structures varying from 1D to 3D with different supramolecular architectures. 1 is a 1D single-chain structure, in which trinuclear water clusters link adjacent triflate anions to form 1D supramolecular helix. 2 is composed of right-helical Cu(II) bis-triazole chains, which are interlinked via copper(II) ions as hingers forming a novel 2D layered structure. Eight-member supramolecular cycles constructed by coordinated water molecules and free triflate anions are found to be embedded into the 2D planes of 2. 3 contains 2D planar nanogrid networks stacked in an AB stacking fashion. Triple Cl···H−C hydrogen bonds reside between these 2D layers. 4 is a 3D MOF with large 1D rhombic channels with dimensionalities of 10.102 × 14.067 Ų accommodating BF₄⁻ anions, which also represents the first case of metal bis-triazole compound with CdSO₄ topology. For 1−4, FT-IR and elemental analysis has been carried out, and the conformational variation of L also has been briefly discussed.