Synthesis, characterization, crystal structures and thermal and photoluminescence studies of dimethylpyrazine-carboxylate mixed ligand silver(i) coordination polymers with various multinuclear silver units

Abstract

Seven new silver(I) coordination compounds based on dimethylpyrazine (dmpyz), [Ag₄(2,5-dmpyz)(ndc)₂]_n (1), [Ag₂(2,5-dmpyz)(pma)_0.5]_n (2), [Ag₄(2,3-dmpyz)₂(mpa)₂]_n (3), [Ag₂(2,3-dmpyz)(npa)]_n (4), [Ag(2,3-dmpyz)_0.5(opa)_0.5]_n (5), [Ag₆(2,3-dmpyz)₃(mpa)₃]_n (6) and [Ag₆(2,3-dmpyz)₂(tma)₂·5H₂O]_n (7), have been synthesized and have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. In compound 1, two types of Ag₄ units are linked by organic ligands to form a three-dimensional supramolecular framework. Compound 2 also shows a 3D network structure based on [Ag₄O₂] six-membered rings. Compounds 3 and 6 are both 2D 4⁴-sql nets, in which Ag₄ units and Ag₆ units are observed, respectively. In compound 4, the npa ligand adopts a μ₅-η¹:η¹:η¹:η² mode to link zigzag Ag₄ subunits (SBUs), giving a 2D network. Compound 5 shows a 1D infinite silver chain clamped by the opa ligands. In 7, six coordinated Ag(I) ions propagate to an infinite 1D silver strap and the 2,3-dmpyz and tma ligands link the silver strap into a 3D framework. The high structural diversity of the compounds and the Ag units is highly dependent on the solvent and the coordination mode of the carboxylate. The thermal stabilities and photoluminescence behaviours of the compounds were also discussed.