Synthesis, crystal structures and fluorescence of cadmium(II) coordination polymers with derivatives of pyrazine-1,4-dioxide and thiocyanate as mixed-bridging ligands

Abstract

Two Cd(II) coordination polymers have been synthesized with derivatives of pyrazine-1,4-dioxide and thiocyanate anion as bridging ligands and structurally determined by X-ray crystallography. Complex 1, [Cd(μ1,3-SCN−)2(μ1,6-L1)] n (L1 = 2,5-dimethylpyrazine-1,4-dioxide), belongs to the triclinic, space group P 1 with a = 5.7627(18) Å, b = 7.182(2) Å, c = 7.509(2) Å, α = 74.042(3)°, β = 84.766(4)°, γ = 88.162(4)°; complex 2, [Cd2(μ1,3-SCN−)4(μ4-L2)] n (L2 = 2,3,5,6-tetramethylpyrazine-1,4-dioxide), crystallizes in a monoclinic system with space group C2/m with a = 10.194(4) Å, b = 13.491(6) Å, c = 8.140(3) Å, β = 120.372(4)°. Complex 1 shows a two-dimensional sheet structure, and in a direction the Cd(II) ions were coordinated by μ1,3-SCN− forming the one-dimensional chain and the L1 bridging ligand made the chains connect in the c direction leading to formation of a two-dimensional sheet on the ac plane. For 2 the one-dimensional chains in the a axis were constructed by coordination of μ1,3-SCN− bridging ligands with the Cd(II) ions, and in b and c directions the chains were joined by L2 bridging ligands leading to a three-dimensional structure. In 2 L2 displays a μ4-bridging coordination mode. Both complexes exhibit strong fluorescence emission.