Series of 3d-4f heterometallic coordination polymers: Structures, near-infrared luminescence and magnetic properties

A series of 3d-4f heterometallic coordination polymers (CPs), namely, Ln2(CuL)2(nipt)3(H2O)]⋅nH2O (Ln = Sm 1, Nd 2, Gd 3, for 1–2 n = 2, for 3 n = 1.6), [Yb2(CuL)4(nipt)3]·3.5H2O (4), [Pr2(NiL)(nipt)3(H2O)]⋅1.5H2O (5), [Sm2(NiL)(nipt)3(H2O)2]CH3OH⋅H2O (6), [Er2(NiL)2(nipt)3(H2O)2]⋅3H2O (7) (ML, H2L = 2, 3-dioxo-5, 6, 14, 15-dibenzo-1, 4, 8, 12-tetraazacyclo-pentadeca-7, 13-dien; H2nipt = 5-nitroisophthalic acid) were obtained by a solvothermal method and structurally characterized. Complexes 1–3 have 3,3,4,5-connected (3.4.5)(32.42.5.63.72)(42.63.8)(42.6) topological structure consisting of two different chains. 4 exhibits a two-dimensional (2D) heterometallic structure with 3-connected (63) topology. 5 displays a 2D framework formed by four-strand meso-helical chains and characterized by 6,6,4,4,4-connected (411.64)(412.63)(43.62.8)(45.6)2 topology. Compound 6 has 3,4,4,3-connected (43)(44.62)(42.124)(42.6) topological structure formed by three-strand meso-helical chains. In 7, two kinds of μ3-bridged nipt2− ligands together with NiL connect the eight-coordinated Er3+ ions to form a 2D structure, and the 2D layers are extended by μ2-bridged nipt2− into a three-dimensional (3D) microporous framework with 4,4,3,3-connected (4.62.83)2(4.82)2 topology. Interestingly, for 1, 2 and 4, CuL-sensitized the near-infrared emissions form Sm(III), Nd(III) and Yb(III) were firstly found under visible light irradiation. Moreover, the magnetic properties of 1, 2, 4 and 5 are also discussed.