Cracking the framework of bulk CuCN with flexible bipyrazolyl-based ligands to assemble [CuCN]n-based coordination polymers

Abstract

Solvothermal reactions of CuCN with a set of flexible bipyrazolyl-based ligands with different spacer lengths [(dmpz)(CH₂)_n(dmpz)] (dmpz = 3,5-dimethyl-pyrazolyl; n = 1–6) gave rise to six [CuCN]_n-based coordination polymers [(CuCN)₃L]_n (1: L = dmpzm; 2: L = dmpze), [(CuCN)₂L]_n (3: L = dmpzpr; 4: L = dmpzb; 5: L = dmpzp; 6: L = dmpzh). Compounds 1–6 were characterized by elemental analysis, IR, powder X-ray diffraction and single-crystal X-ray diffraction. 1 or 2 exhibits a 1D scolopendra-like chain assembled from a rare 1D zigzag [CuCN]_n chain with [CN–Cu–CN–Cu–L] (1: L = dmpzm; 2: L = dmpze) side arms. 3 or 4 shows a 2D (6,3) wave-like layer in which [Cu₆(μ-CN)₆L₂]_n (L = dmpzpr or dmpzb) double chains are interconnected by pairs of L bridges. 5 consists of two [CuCN]_n single chains that are linked by dmpzp bridges to form a rare 1D chain with an oblong channel. 6 has a 3D network in which the 2D [Cu₁₀(μ-CN)₁₀(dmpzh)₃]_n layers are interconnected by pairs of dmpzh bridges. In addition, the photoluminescent properties of 1–6 in the solid state at ambient temperature were investigated.