Two 3D coordination frameworks based on nanosized huge Ln₂₆ (Ln = Dy and Gd) spherical clusters

Two novel three-dimensional (3D) coordination polymers Zn _1.5Dy₂₆(IN)₂₅(CH₃COO) ₈(CO₃)₁₁(OH)₂₆(H₂O) ₂₉ (1) and Zn_1.5Gd₂₆(IN)₂₆(CH ₃COO)₇(CO₃)₁₁(OH) ₂₆(H₂O)₂₈ (2) based on the linkages of large nanosized spherical hydroxo Ln₂₆ clusters and zinc centers by organic ligands have been hydrothermally synthesized. Metal organic framework (MOF) 1 crystallizes in the triclinic space group P1̄, with a = 21.107(2) Å, b = 21.185(2) Å, c = 36.323(4) Å, α = 89.001(2)°, β = 82.486(2)°, γ = 68.359(2)°, V = 14960(3) ų, Z = 2. MOF 2 crystallizes in the triclinic space group P1̄, a = 19.6213(15) Å, b = 22.1850(17) Å, c = 34.654(3) Å, α = 88.5340(210)°, β = 85.6520(10)°, γ = 72.9790(19)° V = 14382.5(19) ų, Z = 2. Structural analysis indicates that both 3D polymers can be constructed using the building unit of CO₃@Ln ₂₆ (Dy for 1, Gd for 2) and exhibit similar topological frameworks. During the synthesis, three ligands were used. CO₃^2- plays a very important role in the formation of the spherical Ln₂₆ cluster. CH₃COO^- makes the Ln₂₆ cluster stable and reduces steric restriction. The isonicotinate (IN) stabilizes the cluster and links the clusters and the Zn centers.