4', 4'', 5', 5''-tetra (2-hydroxyl-benzylideneimino) dibenzo-18- crown-6 (L^1H~4) and its 5-substituted derivatives (substituted group R=CH~3, OH, OCH~3, Cl, NO~2) L^2H~4～L^6H~4 have been synthesized from dibezno-18-crown-6 as starting material. The L^1H~4～L^6H~4 react successively with potassium nitrate and cobalt acetate in air to form 1:1:2 potassium (I)/dicobalt (II) complexes LCo~2.2H~2O. KNO~3 (L=L^5, L^6) or their dioxygen adducts LCo~2(2O~2).2H~2O.KNO~3 (L=L^1～L^4). The influence of the substituted groups R in ligands and potassium ion in the crown ring on formation and stability of dioxygen adducts was investigated. The results indicate that potassium (I)/dicobalt (II) complexes containing electron-withdrawing group (R=Cl, NO~2) can not form dioxygen adducts. Potassium ion in the crown ring leads to difference in the thermostability of the two Co-O~2 bonds in dioxygen adducts. The TG analysis of dioxygen adducts shows that one in two O~2 of LCo~2(2O~2).2H~2O.KNO~3 (L=L^1～L^4) was first lost at 51～115℃ and then the other O~2 was extricated at 125～ 216℃. However, two O~2 molecules in LCo~2(2O~2).2H~2O without potassium ion were liberated together at 51～111℃.

Key words: SCHIFF BASE, CROWN ETHER COMPOUNDS, COBALT COMPLEX, POTASSIUM NITRATE