From (3,6)-Connected kgd, chiral anh to (3,8)-connected tfz-d Nets in Low Nuclear Metal Cluster-Based Networks with Triangular Pyridinedicarboxylate Ligand

Four novel coordination polymers based on asymmetric triangular S-(4'-carboxylphenyl) nicotinic acid (H(2)cpna), namely, Ni(cpna)(H2O)(2)(1) M-2(cpna)(2)(H2O)(3)center dot 0.5H(2)O center dot WDMF [M = Ni for (2), Co for (3)] and Ni-3(Hcpna)(2)(cpna)(2)(H2O)(4)center dot 2H(2)O (4), have been synthesized under solvothermal All of the four compounds contain conditions. low nuclear metal clusters as secondary building units (SBUs). Complex 1 exhibits two-dimensional (3,6)-connected (4(3))(2)(4(6).6(6).8(3))-kgd topology, in which cpna ligands and edge-shared dinuclear SBUs act as 3-connected and 6-connected nodes, respectively. Compounds 2 and 3 are constructed by corner-shared dinuclear SBUs and show an unprecedented (3,6)-connected chiral (4(2).6)(2)(4(4).6(2).8(8).10)-anh (flu-3, P6(2)22) topology. In 4, linear trimers are ligated by six cpna ligands to form a planar (4(3))(2)(4(6).6(6).8(3))-kgd layer, and adjacent layers are further linked by Hcpnaligands through Ni-O and Ni-N bonds to form three-dimensional (3,8)-connected (4(3))(2)(4(6). 6(18).8(4))-yi-d net. Both 1 and 4 crystallize in the triclinic crystal system with symmetric space group 151, which result in an equal ratio of (R)- and (S)-cpna isomers. Isostructural 2 and 3 crystallize in a trigonal crystal system with the chiral space group P3221, and a single crystal contains a sole optical isomer of cpna, although bulk crystals are a racemic mixture. Variable-temperature magnetic susceptibility measurements reveal ferromagnetic coupling of edge-shared dimers in 1, antiferromagnetic coupling of corner-shared dimers in 2 and 3, and ferrimagnetic coupling of linear trimers in 4.