Nickel(II) Coordination Polymers Supported by Bis-pyridyl-bis-amide and Angular Dicarboxylate Ligands: Role of Ligand Flexibility in Iodine Adsorption

Reactions of N,N'-bis(3-pyridylmethyl)oxalamide (L-1), N,N'-bis(4-pyridylmethyl)oxalamide (L-2), or N,N'-bis(3-pyridylmethyl)adipoamide) (L-3) with angular dicarboxylic acids and Ni(II) salts under hydro(solvo)thermal conditions afforded a series of coordination polymers: {[Ni(L-1)(OBA)(H2O)]center dot H2O}(n) (H(2)OBA = 4,4-oxydibenzoic acid), 1, {[Ni(L-1)(SDA)(H2O)(2)]center dot H2O center dot CH3OH}(n) (H(2)SDA = 4,4-sulfonyldibenzoic acid), 2, {[Ni(L-2)(OBA)]center dot C2H5OH}(n), 3, {[Ni(L-2)(OBA)]center dot CH3OH}(n), 4, {[Ni-2(L-2)(SDA)(2)(H2O)(3)]center dot 5H(2)O}(n), 5, {[Ni-2(L-2)(SDA)(2)(H2O)(3)]center dot H2O center dot 2C(2)H(5)OH}(n), 6, {[Ni(L-3)(OBA)(H2O)(2)]center dot 2H(2)O}(n), 7, {[Ni(L-3)(SDA)(H2O)(2)]center dot 2H(2)O}(n), 8, and {[Ni(L-3)(0).(5)(SDA)(H2O)(2)]center dot 0.5C(2)H(5)OH}(n), 9, which have been structurally characterized by using single-crystal X-ray crystallography. Complex 1 exhibits an interdigitated 2D layer with the 2,4L2 topology and 2 is a 2D layer with the sql topology, while 3 and 4 are 3D frameworks resulting from polycatenated 2D nets with the sql topology and 5 and 6 are 2-fold interpenetrated 3D frameworks with the dia topology. Complexes 7 and 8 are 1D looped chains and 9 is a 2D layer with the 3,4L13 topology. The various structural types in 1-9 indicate that the structural diversity is subject to the flexibility and donor atom position of the neutral spacer ligands and the identity of the angular dicarboxylate ligands, while the role of the solvent is uncertain. The iodine adsorption of 1-9 was also investigated, demonstrating that that the flexibility of the spacer L-1-L-3 ligands can be an important factor that governs the feasibility of the iodine adsorption. Moreover, complex 9 shows a better iodine adsorption and encapsulates 166.55 mg g(-1) iodine in the vapor phase at 60 degrees C, which corresponded to 0.38 molecules of iodine per formula unit.