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 m-xpt (m-xylylenebis(pyridyltriazole)) are investigated upon their interaction with 1,4-diazabicyclo[2.2.2]octane (dabco) and carbon dioxide-enriched air. The binuclear [Cu2(m-xpt)2]4+ complexes react with dabco to produce a carbonate-bridged trinuclear complex, [Cu3(m-xpt)3(µ-CO3)]4+, and an oxalate-bridged binuclear complex, [Cu2(m-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(o-xpt)(PF6)]n, formed from Cu(I) and o-xpt (o-xylylenebis(pyridyltriazole)) coordination, undergoes oxidation in CO2-enriched air to yield a tetranuclear Cu(II) complex, Cu4(o-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.