Cyclam complexes containing silica gels for dioxygen adsorption

Several cyclam incorporating silica gels have been synthesised using three different methods, including a sol–gel approach. These various materials show different textures and the macrocycle contents can reach values up to 1.5 mmol g−1. Cu(II) and Co(II) complexes of these modified silica gels have been studied. Finally, the efficiency of [Co(cyclam)]2+ grafted onto silica for binding dioxygen has been determined using ESR spectroscopy and static volumetric gas uptake measurements. The most efficient material behaves as a high-performance dioxygen binding system, showing a very high affinity for dioxygen ((P1/2)1 = 1.91 Torr) coupled with a large total volume of gas adsorbed at 1 atm (3.0 cm3 g−1).