Tunable structures and magnetic / optical properties of six Cd(II)-based coordination polymers by introducing different para- or dia-magnetic metal ions

One monometallic and five heterometallic coordination polymers (HCPs) based on homophthalic acid (H2HPA), [Cd2(HPA)2(H2O)2]·H2O (1), [CdMn(HPA)2(H2O)2]·H2O (2), [Cd3Co(HPA)4(H2O)4]·2H2O (3), [CdCo(HPA)2(DMSO)(H2O)2] (4), [CdNa2(HPA)2(μ2-H2O)(H2O)] (5) and [Cd2Na2(HPA)3(μ2-H2O)(H2O)2] (6), were synthesized solvothermally. Complexes 1-3 have similar two-dimensional (2D) layer structures except that all or part six-coordinated Cd(II) ions in 1 were replaced by the six-coordinated Mn(II) or Co (II) ion in 2 and 3, respectively. Complex 4 shows an 1D ladderlike structure, and 5 and 6 exhibit different 2D layer structures. The different structures of 3/4 and 5/6 could be assembled directly by controlling the different pH values with other same reaction conditions, respectively. Magnetic studies reveal that the introducing of para-magnetic Mn(II) and Co(II) ions endow antiferromagnetic interarions between the neigboring spins in 2–4, and 2 with isotropic Mn(II) ion displays a significant cryogenic magnetocaloric effect with a maximum −ΔSm value of 19.29 J K−1 kg−1 at 2 K and ΔH = 7 T. In addition, the solid-state photophysical properties of 1, 5 and 6 display blue emissions centered at ca. 453 nm, 448 nm and 428 nm, respectively.