Synthesis of crowned mono-and bis-Schiff bases and dioxygen affinities of their cobalt(II) complexes

Four crowned mono-and bis-Schiff bases, 4'-( 2-hydroxyphenylmethylideneimin o) benzo-15-crown-5 ((LH)-H-1) and 4', 5'-bis( 2-hydroxyphenylmethylideneim ino) benzo-15-crown-5 ((LH2)-H-4) as well as their substituted derivatives (LH)-H-2, (LH2)-H-5 were prepared from benzo-15-crown-5 via nitration, redu ction, and condensation. Equilibrium constants and thermodynamic constants Delta H degrees, Delta S degrees for oxygenation of these crowned cobalt(II ) Schiff bass compleses were measured. The influence of ligand structure an d basicity of axial ligand on the affinities of the complexes for dioxygen was discussed in comparison with uncrowned analogues.