Isolated Magnetic Clusters of Co(II) and Ni(II) within 3-Dimensional Organic Frameworks of 6-Mercaptonicotinic Acid:  Unique Structural Topologies Based on Selectivity for Hard and Soft Coordination Environments

Hydrothermal reaction of the mixed thiolate−carboxylate−aromatic amine ligand, 6-mercaptonicotinic acid (6-mnaH2) with Co(II) and Ni(II) leads to two network coordination solids [M9(6-mna)83-O)2(OH3)2(OH2)6] (M = Co, Ni), 1, and [M2Ni12(6-mna)123-OH)2(OH2)6]·8H2O (M = K, Rb, Cs), 2. These compounds are unusual for two reasons:  they are thiolate-bridged networks and they are three-dimensional lattices which contain isolated metal clusters and chains. The magnetic behavior of these compounds has been studied, showing that 2 contains ferromagnetically coupled Ni6 wheels.