Synthesis, structures, and properties of three coordination compounds based on trinickel clusters extended by phenyldicarboxylate ligands

The reaction between [Ni-3(dpa)(4)(ClO4)(2)] and phenyldicarboxylates led to three coordination compounds based on trinickel clusters [Ni-3(dap)(4)](2+), [Ni-3(dpa)(4)(1,2-Hbdc)(2)]center dot CH2Cl2 center dot H2O (1), {[Ni-3(dpa)(4)(1,2-bdc)]center dot 1.5H(2)O}(n) (2), and {[Ni-3(dpa)(4)(1,2-nbdc)]center dot 1.5H(2)O}(n) (3) where dpa(-) is 2,2'-dipyridylamine anion, 1,2-H(2)bdc is 1,2-benzenedicarboxylic acid, and 1,2-H(2)nbdc is 3-nitro-1,2-benzenedicarboxylic acid. Complexes 2 and 3 were obtained in the case of introducing of water, which is completely different from synthetic methods for previously reported complexes with trinickel clusters [Ni-3(dap)(4)](2+). Complex 1 is a trinickel string complex with two 1,2-Hbdc(-) axial ligands, while complexes 2 and 3 are 1D polymers with bridged phenyldicarboxylates. Axial replacement of phenyldicarboxylates results in some structural changes in the trinickel clusters and some changes of properties, such as solubility, electrochemical behaviour, and fluorescence emission. Desolvated 1 is less stable than those of complexes 2 and 3, indicating the polymeric assemblies enhance the packing stability. The pi-pi interactions occur in complexes 1-3 and the weakest interaction in complex 2. Moreover, complexes 2 and 3 have 1D ladder hydrogen-bonding chains.