钴卟啉的不可逆氧化及含氟聚合物对钴卟啉复合膜氧络合寿命的影响

研究了甲基丙烯酸八氟戊酯 乙烯基咪唑共聚物 (PFIm)与 5 ,1 0 ,1 5 ,2 0 四 (邻 三甲基乙酰胺苯基 )钴卟啉 (TPPCo)复合膜的氧络合百分率随环境湿度和时间的变化 ,讨论了钴卟啉不可逆氧化的机理、动力学 ,及钴卟啉与氧络合的寿命 .空气中的水分子进攻与氧络合的钴卟啉 ,生成过氧化氢自由基和三价钴卟啉 ,是钴卟啉失去与氧络合能力的主要原因 .发现PFIm的憎水性可抑制由水分子引起的钴卟啉的不可逆氧化反应 ,可显著延长钴卟啉与氧络合的寿命 ,从而使含氟的PFIm TPPCo膜与氧络合的寿命要比甲基丙烯酸辛酯 乙烯基咪唑共聚物 (POIm)与钴卟啉复合膜的寿命长

IRREVERSIBLE OXIDATION OF PORPHYRINATO COBALT(Ⅱ)(TPPCo) AND THE EFFECT OF FLUORINE-CONTAINING POLYMERS ON THE LIFETIME OF TPPCo COMPLEX MEMBRANES

The oxidizing process and the oxygen-binding lifetime of 5,10,15,20-tetra( o -pivalamidophenyl)-porphyrinato cobalt(II) (TPPCo) complexed with poly(vinylimidazole- co -fluoropentyl methacrylate) (PFIm) were studied,and the mechanism and dynamics of irreversible oxidation of TPPCo were discussed.The TPPCo displayed a reversible change in the UV-visible absorption spectrum from the deoxy form ( λ max = 530?nm ) to the oxygen-binding one ( λ max = 548?nm ) with an isosbestic point at 538 nm,in response to the partial oxygen pressure of the atmosphere.But the active TPPCo complex in the membrane was slowly changed,via the irreversible oxidation reaction in the open atmosphere,to the TPPCo(Ⅲ) complex without the oxygen-binding ability,which could be monitored by the UV-visible absorption at λ max = 548?nm.In the solid membrane state, water molecules in air may attack the TPPCo-bound dioxygen to yield a hydrodioxy radical and TPPCo(Ⅲ),which is the main reason that diminishes the oxygen-binding ability of the TPPCo complex and that of the membrane.The half-lifetime ( τ ) of the TPPCo complex as an oxygen carrier was measured by allowing the TPPCo-PFIm membrane to stand in dry air (environmental humidity 10%),in laboratory air (humidity ca. 50%),and in a water vapor atmosphere (humidity 95%) at room temperature,respectively.The decrease course of the active TPPCo complex approximately follows the first-order kinetics and gives the t values.The τ value of the PFIm-TPPCo complexed membrane was as long as ca. 250 days even in the water vapor-saturated atmosphere.Under the same laboratory air condition,the lifetime of the PFIm-TPPCo membrane was much longer ( ca. 13 times) than that of the reference non-fluoro membrane such as the membrane of TPPCo complexed with poly(octyl methacrylate- co -vinylimidazole).The hydrophobic property of the PFIm polymer is considered to suppress the irreversible oxidation of the active TPPCo carriers caused by water molecules and to significantly prolong the operational lifetime of the TPPCo complex membrane.