Coordination Polymers Assembled from Angular Dipyridyl Ligands and Cu^II, Cd^II, Co^II Salts:  Crystal Structures and Properties

Six new metal-organic coordination networks based on linking unit 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (L¹) or 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L³) and inorganic Cu^II, Cd^II, and Co^II salts have been prepared and structurally characterized by single-crystal X-ray analysis. Using L¹ to react with three different Cu^II salts, Cu(OAc)₂·H₂O, Cu(NO₃)₂·3H₂O, and CuSO₄·5H₂O, respectively, two different one-dimensional (1-D) coordination polymers, {[Cu₂L¹(μ-OAc)₄](CHCl₃)₂}_n (1) [triclinic, space group P1̄, a = 7.416(3) Å, b = 8.207(3) Å, c = 14.137(5) Å, α = 100.333(7)°, β = 105.013(6)°, γ = 94.547(6)°, Z = 1] and {[CuL¹(NO₃)₂](CHCl₃)_0.5}_n (2) [monoclinic, space group C2/c, a = 28.070(8) Å, b = 9.289(3) Å, c = 15.235(4) Å, β = 113.537(5)°, Z = 8], and a chiral 3-D open framework, {[CuL¹(H₂O)(SO₄)](H₂O)₂}_n (3) [orthorhombic, space group P2₁2₁2₁, a = 5.509(2) Å, b = 10.545(4) Å, c = 29.399(11) Å, Z = 4], were obtained. Reaction of L¹ and Cd(ClO₄)₂·6H₂O or Co(ClO₄)₂·6H₂O, in the presence of NH₄SCN, yielded another 3-D open framework, {[CdL¹(NCS)₂](CH₃OH)_1.5}_n (4) [monoclinic, space group C2/c, a = 28.408(10) Å, b = 9.997(5) Å, c = 7.358(4) Å, β = 99.013(8)°, Z = 4], or a 2-D network, {[Co(L¹)₂(NCS)₂](H₂O)_2.5}_n (5) [orthorhombic, space group Pnna, a = 22.210(5) Å, b = 12.899(3) Å, c = 20.232(4) Å, Z = 4]. When L¹ was replaced by L³ to react with Co(ClO₄)₂·6H₂O and NH₄SCN, another 2-D coordination polymer, [Co(L³)₂(NCS)₂]_n (6) [monoclinic, space group P2₁/c, a = 8.120(3) Å, b = 9.829(4) Å, c = 17.453(6) Å, β = 103.307(6)°, Z = 2], was constructed. These results indicate that the nature of the ligands, metal centers, or counteranions plays the critical role in construction of these novel coordination polymers. The interesting porous natures of two 3-D open frameworks 3 and 4 were investigated by TGA and XPRD techniques, and the magnetic properties of the Cu^II and Co^II complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements.