- 作者: 鄭淑華 ; 陳有順 ; 蘇玉龍
- 作者服務機構: 台灣大學化學系
- 中文摘要: Sterically hindered water-soluble iron(III) tetrakis(sulfonatomesityl)porphine (FeTSMP) exists exclusively in its monomer form in neutral and basic aqueous solutions. The acid dissociation constant (pKa) for Fe/sup III/TSMP is 6.6. The Fe/sup III/II/ TSMP couple has a formal reduction potential at -0.22V (vs. Ag/AgCl) in an acidic buffer solution. The E/sup o'/-pH diagram shows that E/sup o'/ is independent of pH until the pH is larger than the pKa. The acid dissociation constant for Fe/sup II/ TSMP is 11.7. The redox potential of Fe/sup III/II/TSMP shifts positively when imidazole is present, indicating the ligation of imidazole to Fe/sup II/TSMP. At pH 4.0 and 10.2 buffer solutions, two imidazoles are found to ligate at the iron(III) center with .beta./sub 2/=10/sup 4.7/ and 10/sup 4.1/, respectively. The E/sup o'/-pH diagram indicates that the pKa of (ImH)/sub 2/Fe/sup III/TSMP is 11.3 at 0.03M imidazole solution. The oxidation of Fe/sup III/TSMP could involve two one-electron transfer processes, namely, one electron oxidation at the iron center, while another at the porphyrin ring. The two one-electron oxidations are found to overlap at pH=5.5 and separate as the pH increases by shifting of the potential at the iron center, which is pH dependent. The radical cation of porphyrin ring is not stable and decomposes rapidly in water.
- 英文摘要: --
- 中文關鍵字: Iron Porphyrin; Acid Dissociation Constant; Acid-Base Equilibrium; Electrochemistry; Catalysis; Imidazole
- 英文關鍵字: 鐵;樸(???);酸解離常數;酸鹼平衡;電化學;催化(觸媒作用);咪唑