Formation of Strong OH₂···^-O₂C Hydrogen Bonds in a Trinuclear Core-Based Nickel 1,3,5-Benzenetricarboxylate Coordination Polymer

The nickel 1,3,5-benzenetricarboxylate (1,3,5-btc3-) coordination polymer, [Ni6(μ-OH2)4(1,3,5-btc)4(H2O)12]n (1), has been synthesized using a hydrothermal reaction. Trinuclear nickel cores constructed from the μ-OH2 and carboxylate bridges are linked by the 1,3,5-btc3- ligands, forming a two-dimensional network. The μ-OH2 molecules form strong hydrogen bonds with the free oxygens of the carboxylate groups in the trinuclear clusters. A structural phase transition occurs around 373 K and is categorized as a second-order phase transition.