Electronic Structure and Reactivity of Low-Spin Fe(III)-Hydroperoxo Complexes: Comparison to Activated Bleomycin
详细信息 查看全文
- 作者：Nicolai Lehnert ; Frank Neese ; Raymond Y. N. Ho ; Lawrence Que ; Jr. ; and Edward I. Solomon
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：September 11, 2002
- 年：2002
- 卷：124
- 期：36
- 页码：10810 - 10822
- 全文大小：301K
- 年卷期：v.124,no.36(September 11, 2002)
- ISSN：1520-5126
文摘
The spectroscopic properties, electronic structure, and reactivity of the low-spin Fe(III)-hydroperoxo complex [Fe(N4Py)(OOH)]2+ (1, N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine)are investigated in comparison to those of activated bleomycin (ABLM). Complex 1 is characterized byRaman features at 632 (Fe-O stretch) and 790 cm-1 (O-O stretch), corresponding to a strong Fe-Obond (force constant 3.62 mdyn/Å) and a weak O-O bond (3.05 mdyn/Å). The UV-vis spectrum of 1shows a broad absorption band around 550 nm that is assigned to a charge-transfer transition from thehydroperoxo 
to a t2g d orbital of Fe(III) using resonance Raman and MCD spectroscopies and densityfunctional (DFT) calculations. Compared to low-spin [Fe(TPA)(OHx)(OOtBu)]x+ (TPA = tris(2-pyridylmethyl)amine, x = 1 or 2), an overall similar Fe-OOR bonding results for low-spin Fe(III)-alkylperoxo and-hydroperoxo species. Correspondingly, both systems show similar reactivities and undergo homolyticcleavage of the O-O bond. From the DFT calculations, this reaction is more endothermic for 1 due to thereduced stabilization of the 
OH radical compared to OtBu and the absence of the hydroxo ligand thathelps to stabilize the resulting Fe(IV)=O species. In contrast, ABLM has a somewhat different electronicstructure where no 
donor bond between the hydroperoxo ligand and iron(III) is present [Neese, F.; Zaleski,J. M.; Loeb-Zaleski, K.; Solomon, E. I. J. Am. Chem. Soc. 2000, 122, 11703]. Possible reaction pathwaysfor ABLM are discussed in relation to known experimental results.
to a t2g d orbital of Fe(III) using resonance Raman and MCD spectroscopies and densityfunctional (DFT) calculations. Compared to low-spin [Fe(TPA)(OHx)(OOtBu)]x+ (TPA = tris(2-pyridylmethyl)amine, x = 1 or 2), an overall similar Fe-OOR bonding results for low-spin Fe(III)-alkylperoxo and-hydroperoxo species. Correspondingly, both systems show similar reactivities and undergo homolyticcleavage of the O-O bond. From the DFT calculations, this reaction is more endothermic for 1 due to thereduced stabilization of the OH radical compared to OtBu and the absence of the hydroxo ligand thathelps to stabilize the resulting Fe(IV)=O species. In contrast, ABLM has a somewhat different electronicstructure where no donor bond between the hydroperoxo ligand and iron(III) is present [Neese, F.; Zaleski,J. M.; Loeb-Zaleski, K.; Solomon, E. I. J. Am. Chem. Soc. 2000, 122, 11703]. Possible reaction pathwaysfor ABLM are discussed in relation to known experimental results.