Solvothermal Synthesis and Diverse Coordinate Structures of a Series of Luminescent Copper(I) Thiocyanate Coordination Polymers Based on N-Heterocyclic Ligands

Solvothermal reactions of CuSCN with 4-amine-3,5-bis(3-pyridyl)-1,2,4-triazole (3-Abpt), 5-(4-pyridyl)tetrazole (4-Ptz), and 2-(n-pyridyl)benzimidazole (n-PyHBIm, n = 4, 3, 2) in acetonitrile afford six novel coordination polymers: [Cu₅(SCN)₅(3-Abpt)₂]_n (1), [Cu(SCN)(3-Abpt)]_n (2), [Cu(SCN)(4-Ptz)]_n (3), [Cu₂(SCN)₂(4-PyHBIm)]_n (4), [Cu₂(SCN)₂(3-PyHBIm)]_n (5), and [Cu₂(SCN)₂(2-PyBIm)(2-PyHBIm)]_n (6). All these complexes were structurally characterized by X-ray diffraction analysis. 1 is the first example of a 1,1,1,3-μ₄-tetradentate thiocyanate complex which displays a three-dimensional (3D) polymeric framework constructed from thiocyanate and tetradentate 3-Abpt. 2 exhibits a two-dimensional (2D) 4.8² network constructed from unidentate thiocyanate and tridentate 3-Abpt. 3 is a one-dimensional (1D) ladder-like double-chain polymer assembled by bidentate thiocyanate and 4-Ptz ligands. 4 shows a 2D 1,1,3-μ₃-thiocyanate copper 4.8² network where bidentate 4-PyHBIm locates at both sides of the 2D layer. 5 displays a 2D 6³ network constructing from 1,1,3-μ₃-thiocyanate and bidentate 3-PyHBIm. 6 is a 1D 2₁ helical chain polymer constructing from 1,3-μ₂-thiocyanate and 2-PyBIm anion. Bond valence sum (BVS) analysis and magnetic susceptibility indicate that 6 is a mixed-valence compound. The coordinate diversity of thiocyanate is discussed. 1−6 are all thermally stable up to 230−290 °C. They exhibit yellow or blue luminescence originating from ligand-to-metal charge transfer or ligand-centered emission.