The oxygenation constants and thermodynamic parameters (Delta H-o, Delta S-o) of a series of novel Co(II) dihydroxamic acids containing a central functional group (-OCH3) (CoLCoL6)-Co-1 were measured, their catalytic performance in the oxidation of p-xylene to p-toluic acid (PTA) were examined. The influence of` ligand structure, the substituents (X = Cl, OCH3 and Y = H, CH3, Cl) of the aromatic rings and added alkaline cations on the O-2-binding capabilities and catalytic oxidation activities were investigated.