Design, Synthesis and XRD Structural Characterization of New Coordination Polymers Based on Trinuclear Unit [Cu3(μ3-OH)(pz)3]2+ (pz=pyrazolate ion) and Mono- or bicarboxylates

Coordination Polymers (CPs) are multifunctional materials having applications especially in catalysis and gas storage, which originates from high porosity and regularly dispersed coordination metal sites. Here we report the syntheses of CPs, incorporating an active trinuclear triangular copper(II) site, [Cu3(μ3-OH)(μ-pz)3]2+, by employing different bicarboxylate linkers having various size, flexibility, steric hindrance and conformational freedom. Moreover, also chiral (S)-2-Methylsuccinate, besides its racemic mixture, was employed. The analysis of the structural peculiarities induced by these building blocks was carried out by using single crystal X-ray diffraction (SC-XRD). The precise atomic positions of the three-dimensional packing allow defining pores sizes, shapes and surface structures suggesting structure-property relationships. Structure determination evidenced that bicarboxylates permits trinuclear moieties further self-assemble to generate CPs and that different reaction conditions may generate different CPs through specific coordination ways of carboxylate group. In addition, structure visualizations highlighted the relevant role of specific supramolecular interactions (particularly H-bonds) in the molecular assemblies. CPs presenting porous structures showed a phase transition to a compact arrangement after solvent removal according to a 1° generation porosity.