Structural diversity and modification in Ni(II) coordination polymers: a peculiar phenomenon of reversible structural transformation between a 1D ladder and 2D layer

Reactions of metal(ii) salts (M = Cd, Ni and Zn) with 5-tert-butylbenzene-1,3-dicarboxylic acid (5-tert-H(2)IPA) and N,N '-bis(3-pyridyl)terephthalamide (L-1) or N,N '-bis(4-pyridyl)terephthalamide (L-2) afforded {[Cd(L-1)(5-tert-IPA)(H2O)]center dot 2H(2)O}(n), 1, {[Ni(L-1)(1.5)(5-tert-IPA)(H2O)(2)]center dot 2.5H(2)O}(n), 2, {[Ni(L-1)(5-tert-IPA)(CH3OH)]center dot 2CH(3)OH}(n), 3, [Zn(L-1)(0.5)(5-tert-IPA)](n), 4, and {[Ni(L-2)(5-tert-IPA)(H2O)]center dot 2H(2)O}(n), 5, which have been structurally determined by using single-crystal X-ray diffraction. Complexes 1 and 2 are 1D ladders with the {4 center dot 8(4)center dot 12}{4}{8}-2,2,4C1 and {8(2)center dot 12}(2){8}(3)-2,2,3C4 topologies, and 3 and 5 are 2D layers showing {8(4)center dot 12(2)}{8}(2)-2,4L2 and {4(4)center dot 6(2)}-sql topologies, respectively, while complex 4 exhibits a 3-fold interpenetrated 3D net with the {4(2)center dot 6 center dot 10(2)center dot 12}{4(2)center dot 6}-coe-3,4-C2/c topology, which can be further simplified as the {6(5)center dot 8}-cds topology, indicating that solvents and metal identity play important roles in determining the structural diversity. Moreover, complexes 2 and 3 display a reversible structural transformation upon coordination as well as co-crystallized solvent exchange between H2O and CH3OH, which can be ascribed to the alternations of the bonding modes of the 5-tert-IPA(2-) ligand upon solvent attack, together with the conformation changes of the L-1 ligand. Their thermal decomposition and the luminescence properties of 1 and 4 are also discussed.