Vibrational Assignments of Six-Coordinate Ferrous Heme Nitrosyls: New Insight from Nuclear Resonance Vibrational Spectroscopy

This Communication addresses a long-standing problem: the exact vibrational assignments of the low-energy modes of the Fe−N−O subunit in six-coordinate ferrous heme nitrosyl model complexes. This problem is addressed using nuclear resonance vibrational spectroscopy (NRVS) coupled to 15N18O isotope l...

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Bibliographic Details
Published in:Inorganic chemistry 2008-12, Vol.47 (24), p.11449-11451
Main Authors: Paulat, Florian, Berto, Timothy C, DeBeer George, Serena, Goodrich, Lauren, Praneeth, V. K. K, Sulok, Corinne D, Lehnert, Nicolai
Format: Article
Language:English
Subjects:
Electron Spin Resonance Spectroscopy - methods
Heme - chemistry
Kinetics
Models, Molecular
Molecular Conformation
Nitrogen Isotopes
Nitrogen Oxides - chemistry
Oxygen Isotopes
Spectrum Analysis
Thermodynamics
Vibration
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Summary:This Communication addresses a long-standing problem: the exact vibrational assignments of the low-energy modes of the Fe−N−O subunit in six-coordinate ferrous heme nitrosyl model complexes. This problem is addressed using nuclear resonance vibrational spectroscopy (NRVS) coupled to 15N18O isotope labeling and detailed simulations of the obtained data. Two isotope-sensitive features are identified at 437 and 563 cm−1. Normal coordinate analysis shows that the 437 cm−1 mode corresponds to the Fe−NO stretch, whereas the 563 cm−1 band is identified with the Fe−N−O bend. The relative NRVS intensities of these features determine the degree of vibrational mixing between the stretch and the bend. The implications of these results are discussed with respect to the trans effect of imidazole on the bound NO. In addition, a comparison to myoglobin-NO (Mb-NO) is made to determine the effect of the Mb active site pocket on the bound NO.
ISSN:0020-1669
1520-510X
DOI:10.1021/ic801626w