Structural Rearrangement in Cyclic Cu(II) Pyridyltriazole Complexes: Oxidation of Dabco to Oxalate and CO2 Conversion to Carbonate

Structural rearrangements in metal-organic supramolecules constructed from the coordination of Cu(II) with <i>m</i>-xpt (<i>m</i>-xylylenebis(pyridyltriazole)) are investigated upon their interaction with 1,4-diazabicyclo[2.2.2]octane (dabco) and carbon dioxide-enriched air. The binuclear [Cu₂(<i>m</i>-xpt)₂]⁴⁺ complexes react with dabco to produce a carbonate-bridged trinuclear complex, [Cu₃(<i>m</i>-xpt)₃(µ-CO₃)]⁴⁺, and an oxalate-bridged binuclear complex, [Cu₂(<i>m</i>-xpt)₂(µ-C₂O₄)]²⁺, where carbonate and oxalate likely originate from CO₂ and dabco, respectively. The trinuclear complex reassembles the original dimer upon the removal of the carbonate ion. Similarly, polymeric [Cu(<i>o</i>-xpt)(PF₆)]_n, formed from Cu(I) and <i>o</i>-xpt (<i>o</i>-xylylenebis(pyridyltriazole)) coordination, undergoes oxidation in CO₂-enriched air to yield a tetranuclear Cu(II) complex, Cu₄(<i>o</i>-xpt)₃(μ₄-CO₃)(μ₂-OH)(μ₂-OCOCH₃)⁴⁺. The reaction progress is monitored by UV-Vis spectroscopy, and the major products are characterized by single-crystal X-ray diffraction.