Unusual Oxidation of an N-Heterocycle Ligand in a Metal−Organic Framework

An in situ ligand reaction from the pyridine cycle to −COO^- in the copper−organic framework is achieved under hydrothermal conditions. Compound [Cu₂(bpa)₄] [1; bpa = 5-(4-bromophenyl)picolinic acid] exhibits a one-dimensional chain architecture based on weak Cu−O interactions. The mechanism of ligand transformation is discussed.