From (3,6)-Connected kgd,chiral anhto (3,8)-connected tfz-dNetsin Low Nuclear Metal Cluster-Based Networks with Triangular PyridinedicarboxylateLigand.

Four novel coordinationpolymers based on asymmetric triangular5-(4′-carboxylphenyl) nicotinic acid (H2cpna), namely,Ni(cpna)(H2O)2(1), M2(cpna)2(H2O)3·0.5H2O·DMF [M = Ni for (2), Co for (3)]and Ni3(Hcpna)2(cpna)2(H2O)4·2H2O (4), have been synthesizedunder solvothermal conditions. All of the four compounds contain lownuclear metal clusters as secondary building units (SBUs). Complex 1exhibits two-dimensional (3,6)-connected (43)2(46.66.83)-kgdtopology, in which cpna ligands and edge-shared dinuclear SBUs actas 3-connected and 6-connected nodes, respectively. Compounds 2and 3are constructed by corner-shared dinuclearSBUs and show an unprecedented (3,6)-connected chiral (42.6)2(44.62.88.10)-anh(flu-3, P6222) topology. In 4, linear trimers are ligated by sixcpna ligands to form a planar (43)2(46.66.83)-kgdlayer, and adjacentlayers are further linked by Hcpna–ligands throughNi–O and Ni–N bonds to form three-dimensional (3,8)-connected(43)2(46.618.84)-tfz-dnet. Both 1and 4crystallize in the triclinic crystal system with symmetric spacegroup P̅1, which result in an equal ratio of(R)- and (S)-cpna isomers. Isostructural 2and 3crystallize in a trigonal crystal systemwith the chiral space group P3221, anda single crystal contains a sole optical isomer of cpna, althoughbulk crystals are a racemic mixture. Variable-temperature magneticsusceptibility measurements reveal ferromagnetic coupling of edge-shareddimers in 1, antiferromagnetic coupling of corner-shareddimers in 2and 3, and ferrimagnetic couplingof linear trimers in 4. [ABSTRACT FROM AUTHOR]