Seven 3d-4f coordination polymers of macrocyclic oxamide with polycarboxylates: Syntheses, crystal structures and magnetic properties

Seven new 3d–4f heterometallic coordination polymers, [Ln(CuL)₂(Hbtca)(btca)(H₂O)]·2H₂O (Ln = Tb^III1, Pr^III2, Sm^III3, Eu^III4, Yb^III5), [Nd(NiL)(nip)(Rnip)]·0·25H₂O·0.25CH₃OH (R= 0.6CH₃, 0.4H) 6 and [Nd₂(NiL)(nip)₃(H₂O)]·2H₂O 7(CuL or NiL, H₂L = 2, 3-dioxo-5, 6, 14, 15-dibenzo-1, 4, 8, 12-tetraazacyclo-pentadeca-7, 13-dien; H₂btca = benzotriazole-5-carboxylic acid; H₂nip = 5-nitroisophthalic acid) have been synthesized by a solvothermal method and characterized by single-crystal X-ray diffraction. Complexes 1–5 exhibit a double-strand meso-helical chain structures formed by [Ln^IIICu^II₂] units via the oxamide and benzotriazole-5-carboxylate bridges, while complex 6 exhibits a four-strand meso-helical chain formed by NdNi unit via the oxamide and 5-nitroisophthalate bridges. Complex 7 consists of a 2D layer framework formed by four-strand meso-helical chain via the nip²⁻ bridges. Moreover, the magnetic properties of them were investigated, and the best-fit analysis of χ_MT versus T show that the anisotropic contribution of Ln(III) ions (arising from the spin-orbit coupling or the crystal field perturbation) dominates (weak exchange limit) in these complexes(for 3, λ = 214.6 cm⁻¹, zj' = −0.33 cm⁻¹, g_av = 1.94; for 5, Δ = 6.98 cm⁻¹, zj' = 1.53 cm⁻¹, g_av = 1.85). - Graphical-abstract: Seven novel oxamido-bridged 3d-4f heterometallic coordination polymers with benzotriazole-5-carboxylate or 5-nitroisophthalate co-ligands under solvothermal reaction conditions. Polymers 1–7 hold 1D or 2D framework structure, viz., double-strand meso-helical chain of 1–5, four-strand meso-helical chain of 6, and 2D net of 7 consisting of four-strand meso-helical chain. Moreover, the temperature dependences of magnetic susceptibilities of compounds 1–7 were also studied.