The Diagnostic Vibrational Signature of Pentacoordination in Heme Carbonyls

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• 作者：Douglas P. Linder ; Nathan J. Silvernail ; Alexander Barabanschikov ; Jiyong Zhao ; E. Ercan Alp ; Wolfgang Sturhahn ; J. Timothy Sage ; W. Robert Scheidt ; Kenton R. Rodgers
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：July 16, 2014
• 年：2014
• 卷：136
• 期：28
• 页码：9818-9821
• 全文大小：304K
• ISSN：1520-5126

文摘

Heme-carbonyl complexes are widely exploited for the insight they provide into the structural basis of function in heme-based proteins, by revealing the nature of their bonded and nonbonded interactions with the protein. This report presents two novel results which clearly establish a FeCO vibrational signature for crystallographically verified pentacoordination. First, anisotropy in the NRVS density of states for 谓_Fe鈥揅 and 未_FeCO in oriented single crystals of [Fe(OEP)(CO)] clearly reveals that the Fe鈥揅 stretch occurs at higher frequency than the FeCO bend and considerably higher than any previously reported heme carbonyl. Second, DFT calculations on a series of heme carbonyls reveal that the frequency crossover occurs near the weak trans O atom donor, furan. As 谓_Fe鈥揅 occurs at lower frequencies than 未_FeCO in all heme protein carbonyls reported to date, the results reported herein suggest that they are all hexacoordinate.