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 21 . Cu(II) and Co(II) complexes of these modified silica gels have been studied. Finally, the efficiency of [Co(cyclam)] 21 grafted onto silica for binding dioxygen has been determined using ESR spectroscopy and static volumetric gas uptake measurements. The most

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... fficient material behaves as a high-performance dioxygen binding system, showing a very high affinity for dioxygen ((P 1/2 ) 1~1 .91 Torr) coupled with a large total volume of gas adsorbed at 1 atm (3.0 cm 3 g 21 ).