Influence of hydrothermal synthesis temperature on the structures of two 3D coordination polymers

Two 3D coordination polymers [Zn(μ₄-dmbdc)]_n, 1 and [Zn₅(μ₃-OH)₄(μ₅-dmbdc)₂(μ₄-dmbdc)]_n, 2 (H₂dmbdc = 2,5-dimethylbenzenedicarboxylic acid) have been prepared by hydrothermal syntheses with temperature as the only variable. The structure feature is the presence of monoatomic coordination bridges, i.e. μ₃-OH and μ₂-O (from μ₃-COO⁻ of μ₅-dmbdc) in 2 synthesized at higher temperature. The coordination number of zinc ion and the bridging number of the carboxyl group increase with the increasing synthesis temperature, resulting in the formation of the more stable and condensed phase.