Obare Sherine O, Ito Tamae, Meyer Gerald J
Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
J Am Chem Soc. 2006 Jan 25;128(3):712-3. doi: 10.1021/ja055908+.
Hemin (iron protoporphyrin IX) has been anchored to approximately 15 nm TiO2 nanocrystallites (anatase) in approximately 8 mum thick mesoporous thin films. Band gap excitation of these materials in methanol or aqueous (pH 4 or 8) solutions leads to the reduction of hemin to heme (FeIII --> FeII) and the production of TiO2(e-), heme/TiO2(e-). The mechanisms and second-order rate constants for the reduction of bromobenzene, chlorobenzene, dichlorobenzene, and trichloroethylene were quantified. In all cases, the concentration of TiO2(e-) was found to decrease to near zero before the hemes were oxidized to hemin. Comparative studies with TiO2(e-) that were not functionalized with hemes indicate that organohalide reduction is mediated by the hemes. Reactions of 6-bromo-1-hexene with heme/TiO2(e-) demonstrate multi-electron transfer reactivity and show that heme/TiO2(e-) nanocrystallites deliver two electrons to RX within 4.5 mus.
血红素（铁原卟啉IX）已被固定在约8微米厚的介孔薄膜中约15纳米的二氧化钛纳米晶体（锐钛矿）上。这些材料在甲醇或水性（pH值为4或8）溶液中的带隙激发导致血红素还原为亚铁血红素（FeIII→FeII），并产生TiO2（e-）、血红素/TiO2（e-）。对溴苯、氯苯、二氯苯和三氯乙烯还原的机制和二级速率常数进行了量化。在所有情况下，发现TiO2（e-）的浓度在血红素被氧化为血红素之前降至接近零。与未用血红素功能化的TiO2（e-）的比较研究表明，有机卤化物的还原是由血红素介导的。6-溴-1-己烯与血红素/TiO2（e-）的反应显示了多电子转移反应性，并表明血红素/TiO2（e-）纳米晶体在4.5微秒内将两个电子传递给RX。
