The oxygenation constants and thermodynamic parameter (?Ho, ?So) of a series of novel Co (II) complexes with phenol ether bridged dihydroxamic acids CoL1-CoL6 were measured, their catalytic performance in oxidation of p-xylene to p-toluic acid (PTA) were examined. The modulation of O2-binding capabilities and catalytic oxidation activities by X (X = Cl, OCH3) and Y (Y = H, CH3, Cl) groups bonded to the aromatic rings of the Co (II) complexes were investigated. The oxygenation constants and thermodynamic parameters (? Ho,? So) of a series of novel Co (II) complexes with phenol ether bridged dihydroxamic acids CoL1-CoL6 were measured, their catalytic performance in oxidation of p-xylene to p-toluic acid The modulation of O2-binding capabilities and catalytic oxidation activities by X (X = Cl, OCH3) and Y (Y = H, CH3, Cl) groups bonded to the aromatic rings of the Co (II) complexes were investigated.