Cobalt(II) salen complex with two aza-crown pendants and its analogues as synthetic oxygen carriers
Abstract
Salen with two aza-crown ether pendants H2L1 and its analogues H2L2-H2L4 were successfully synthesized starting from benzo-10-aza-15crown-5 (BN15C5) or morpholine. Their structures were characterized by IR, MS, 1H NMR and elemental analysis, and were confirmed by X-ray diffraction analysis of H2L1. Moreover, the saturated oxygen uptake of their cobalt(II) complexes CoL1-CoL4 in diethyleneglycol dimethyl ether was determined at different temperature. The oxygenation contants (KO2 ) and thermodynamic parameters (ΔH° and ΔS°) were calculated. The modulation of O2-binding capabilities by pendant substituents were investigated as compared with the parent Schiff base complex CoL5 (CoSalen). The results indicate that the dioxygen affinities of CoL have been much more enhanced by aza-crown pendants than that by morpholino pendants, and the O2-binding capabilities of CoL1 and CoL2 with aza-crown pendants would also be enhanced by adding alkali metal cations.
