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

A series of 3d-4f heterometallic coordination polymers (CPs), namely, Ln(2)(CuL)(2)(nipt)(3)(H2O)center dot nH(2)O (Ln = Sm 1, Nd 2, Gd 3, for 1-2 n = 2, for 3 n = 1.6), [Yb-2(CuL)(4)(nipt)(3)]center dot 3.5H(2)O (4), (Pr-2(NiL)(nipt)(3)(H2O)center dot 1.5H(2)O (5), [Sm-2(NiL)(nipt)(3)(H2O)(2)]CH3OH center dot H2O (6), (Er-2(NiL)(2)(nipt)(3)(H2O)(2)]center dot 3H(2)O (7) (ML, H2L = 2, 3-dioxo-5, 6, 14, 15-dibenzo-1, 4, 8, 12-tetraazacyclo-pentadeca-7, 13-dien; H(2)nipt = 5-nitroisophthalic acid) were obtained by a solvothermal method and structurally characterized. Complexes 1-3 have 3,3,4,5-connected (3.4.5)(3(2).4(2).(.)5.6(3).7(2))(4(2).6(3).8)(4(2).6) topological structure consisting of two different chains. 4 exhibits a two-dimensional (2D) heterometallic structure with 3-connected (6(3)) topology. 5 displays a 2D framework formed by four-strand meso-helical chains and characterized by 6,6,4,4,4-connected (4(11).6(4))(4(12).6(3))(4(3).6(2).8)(4(5).6)(2) topology. Compound 6 has 3,4,4,3-connected (4(3))(4(4).6(2))(4(2).12(4))(4(2).6) topological structure formed by three-strand meso-helical chains. In 7, two kinds of mu(3)-bridged nipt(2-) ligands together with NiL connect the eight-coordinated Er3+ ions to form a 2D structure, and the 2D layers are extended by mu(2)-bridged nipt(2-) into a three-dimensional (3D) microporous framework with 4,4,3,3-connected (4.6(2).8(3))(2)(4.8(2))(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.