Dioxygen affinities and catalytic oxidation activities of cobalt complexes with Schiff bases containing crown ether

The stoichiometry of dioxygen uptake of Co complexes with 4′,5′-bis-(5-chloro-2-hydroxyphenylmethylideneimino)benzo-12-crown-4 (1a), 4′,5′-bis(2-hydroxyphenylmethylideneimino)benzo-12-crown-4 (1b), 4′,5′-bis-(5-methoxy-2-hydroxyphenylmethylideneimino)benzo-12-crown-4 (1c), 4′,5′-bis-(5-chloro-2-hydroxyphenylmethylideneimino)benzo-15-crown-5 (2a), 4′,5′-bis(2-hydroxyphenylmethylideneimino)benzo-15-crown-5 (2b), 4′,5′-bis(5-methoxy-2-hydroxyphenylmethylideneimino)benzo-15-crown-5 (2c) were measured in pyridine solution. The equilibrium constants and thermodynamic parameters (ΔH0, ΔS0) of these complexes were calculated. At the same time, their catalytic activities in cyclohexene oxidation to 2-cyclohexen-1-one were examined. The influence of the crown ether ring on the dioxygen affinity of Co complexes at different temperature and the catalytic activities were discussed in comparison with uncrowned analogous complexes.