Anion-directed self-assembly of Cu(ii) coordination compounds with tetrazole-1-acetic acid: syntheses in ionic liquids and crystal structures

Abstract

Reaction of tetrazole-1-acetic acid (1-Htza) with a Cu(II) salt in ionic liquids with different anions, [BMIM]X (BMIM = 1-butyl-3-methylimidazolium; X = Br⁻, BF₄⁻, NTf₂⁻ (NTf₂⁻ = bis((trifluoromethyl)sulfonyl)amide)), afforded five Cu(II) coordination compounds, [Cu₂(1-tza)₄]Br·H₃O·1/3H₂O (1), [Cu₂(1-tza)₄]BF₄·H₃O·H₂O (2), [Cu(μ₂-Cl)(1-tza)(1-Htza)(H₂O)]·0.5H₂O (3), [CuCl(μ₂-Cl)(1-Htza)₂(H₂O)]·H₂O (4), and [CuCl₂(1-Htza)₂]·H₂O (5). Single-crystal X-ray diffraction analyses reveal that 1–5 display various structures, and the 1-tza⁻ ligand exhibits diverse coordination modes. Compounds 1 and 2 possess higher dimensional structures (a 2-D neutral Kagomé topology network for 1 and a 3-D lvt-type topology framework for 2) with fully deprotonated 1-tza⁻ ligands. Compounds 3–5 display lower dimensional structures (1-D, 1-D and 0-D for 3, 4 and 5, respectively) with partly or fully protonated 1-Htza. The anions of ionic liquids have significant influences on the final molecular architectures, which arise from different water miscibility of ionic liquids.