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Mechanism of Ferric Oxalate Photolysis
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2017-06-22 00:00:00 , DOI: 10.1021/acsearthspacechem.7b00026
David. M. Mangiante 1 , Richard D. Schaller 2 , Piotr Zarzycki 1, 3 , Jillian F. Banfield 1, 4 , Benjamin Gilbert 1
Affiliation  

Iron(III) oxalate, Fe3+(C2O4)33–, is a photoactive metal organic complex found in natural systems and used to quantify photon flux as a result of its high absorbance and reaction quantum yield. It also serves as a model complex to understand metal carboxylate complex photolysis because the mechanism of photolysis and eventual production of CO2 is not well understood for any system. We employed pump/probe mid-infrared transient absorption spectroscopy to study the photolysis reaction of the iron(III) oxalate ion in D2O and H2O up to 3 ns following photoexcitation. We find that intramolecular electron transfer from oxalate to iron occurs on a sub-picosecond time scale, creating iron(II) complexed by one oxidized and two spectator oxalate ligands. Within 40 ps following electron transfer, the oxidized oxalate molecule dissociates to form free solvated CO2(aq) and a species inferred to be CO2 based on the appearance of a new vibrational absorption band and ab initio simulation. This work provides direct spectroscopic evidence for the first mechanistic steps in the photolysis reaction and presents a technique to analyze other environmentally relevant metal carboxylate photolysis reactions.

中文翻译:

草酸铁光解的机理

草酸铁(III)Fe 3+(C 2 O 43 3–是一种在自然系统中发现的光活性金属有机配合物,由于其高吸收性和反应量子产率而用于定量光子通量。它也可以作为模型配合物来理解金属羧酸盐配合物的光解作用,因为任何系统都无法很好地理解光解作用和最终产生CO 2的机理。我们采用泵/探针中红外瞬态吸收光谱技术研究草酸亚铁离子在D 2 O和H 2中的光解反应。光激发后最多3 ns。我们发现分子内电子从草酸盐到铁的转移发生在皮秒以下的时间尺度上,产生由一个氧化的和两个旁观者的草酸盐配体络合的铁(II)。内下列电子转移40个ps的,氧化的草酸盐分子解离,以形成溶剂化的游离CO 2(水溶液)和推断为CO一个物种2 -基于一个新的振动吸收带的外观和从头仿真。这项工作为光解反应的第一步机理提供了直接的光谱学证据,并提出了一种分析其他与环境有关的金属羧酸盐光解反应的技术。
更新日期:2017-06-22
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