Direct Structural and Chemical Characterization of the Photolytic Intermediates of Methylcobalamin Using Time-Resolved X-ray Absorption Spectroscopy

Journal Article · Tue Mar 06 00:00:00 EST 2018 · Journal of Physical Chemistry Letters

DOI:https://doi.org/10.1021/acs.jpclett.8b00083· OSTI ID:1437278

Subramanian, Ganesh  ^[1]; Zhang, Xiaoyi  ^[2]; Kodis, Gerdenis ^[1]; Kong, Qingyu  ^[2]; Liu, Cunming ^[2]; Chizmeshya, Andrew ^[1]; Weierstall, Uwe ^[1]; Spence, John ^[1]

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1. Arizona State Univ., Tempe, AZ (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)

Cobalt-carbon bond cleavage is crucial to most natural and synthetic applications of the cobalamin class of compounds, and here we present the first direct electronic and geometric structural characteristics of intermediates formed following photoexcitation of methylcobalamin (MeCbl) using time-resolved X-ray absorption spectroscopy (XAS). We catch transients corresponding to two intermediates, in the hundreds of picoseconds and a few microseconds. Highlights of the picosecond intermediate, which is reduced in comparison to the ground state, are elongation of the upper axial Co-C bond and relaxation of the corrin ring. This is not so with the recombining photocleaved products captured at a few microseconds, where the Co-C bond almost (yet not entirely) reverts to its ground state configuration and a substantially elongated lower axial Co-N_Im bond is observed. In conclusion, the reduced cobalt site here confirms formation of methyl radical as the photoproduct.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division; National Science Foundation (NSF)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1437278
• Journal Information: Journal of Physical Chemistry Letters, Vol. 9, Issue 7; ISSN 1948-7185
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Co-C
Xanes
coordination
fine structure
photolysis