• 作者： 湯明潔;黃文樞
• 作者服務機構： 國立中山大學化學系
• 中文摘要： 本探討描述由 Me Co (TIM)CIO，Me Co (bipy) Cl之循環電位的資料中，量測了在包含一大範圍的自由能變化中，非均相電子轉移的速率。利用電化學技巧對圖表II之動力分析顯示，當外加電位超過標準電位 E = 0.43伏特時，實驗所得的速率常數確可作為真正的電子轉移速率k 的量度，但是當外加電位低於標準伏特時，電子轉移的可逆性漸次重要，因此必須一併考慮反逆的電子轉移速率 k 及由電氧化所產生之中間體的分解速率 f 。電子轉移的可逆性因素 f 及實驗的轉移係數β 為電極動力的連續函數，二者均在完全不可逆與可逆即 0 與 1 之間緩緩變化 Rehm-Weller, Marcus-Agmon-Levine 兩個自由能關係式對電子轉移速率的資料可完全適用，在自由能變化的範圍內其真正的能量障礙分別為Me Co(TIM)CIO ，△G ＝6.28 仟卡／莫耳；Me Co (bipy) Cl，△G＝9.38 仟卡∕莫耳。
• 英文摘要： The measurement of the heterogeneous rate constants for electron transfer from cyclic voltammetric（CV）data over an extended range of free energy change (△G) for the trans-Me Co(TIM)CIO and cis-Me Co(bip) CI systems are described. Kinetic analyses of the electrochemical technique for Scheme IIdemonstrated that as the applied potential 15 beyond the standard potential E , the experimenta rateconstant k represents an accurate measurement of the intrinsic rate constant k for electron transfer.However, as the applied potential drops below E , the reversibility of the electron-transfer process becomesincreasingly more important, and the reverse electron transfer rate constant k and the decompositionrate constant k of the electrogenerated intermediate have to be taken into account. The reversibility fac-tor f as well as the“experimental transfer coefficient β is a continuous function of the electrode kinetics, varying smoothly between nil for total irreversibility and unity for reversibility. The exceilent fit of theresulting rate data to the Rehm-Weller and Marcus-Agmon-Levine free energy relationship is observed withthe intrinsic barrier △G =6.28 kcal/mole for trans-Me Co(TIM)CIO and △G =9.38 kcal /mole for cis-Me Co(bip) CI.
• 中文關鍵字： electrooxidation; dimethylcobalt (III) complexes; electron-transfer; free-energy change
• 英文關鍵字： --