AN EPR STUDY OF THE TRANSFORMATION OF Ni(cyclam)@CB[8] AND Ni(cyclen)@CB[8] INCLUSION COMPOUNDS DURING ANNEALING IN A HYDROGEN ATMOSPHERE
The transformation is studied of the compounds {[Ni(cyclam)]@CB[8]}Cl 2·16H 2O and {cis-[Ni(cyclen)(H 2O)Cl]@CB[8]}Cl×12H 2O during thermal annealing in a temperature range of 20°C to 340°C. Using EPR spectroscopy, {cis-[Ni(cyclen)(H 2O)Cl]@CB[8]}Cl×12H 2O, Ni is found to reduce to the 3d 9 state during annealing in a hydrogen atmosphere yet oxidize to the 3d 7 state in the air at 20°C. In the case of {[Ni(cyclam)]@CB[8]}Cl 2×16H 2O, nickel ions remain in the 3d 8 state after annealing in a hydrogen atmosphere and make a transition to the 3d 7 state after air pumping. In both cases, annealing in a hydrogen atmosphere leads to the decomposition of the nickel complexes; simultaneously, a single line with g = 2.003 appears in the EPR spectra, which is likely to be due to the resulting metal nickel clusters.