The electronic structure and chemical bonding of vitamin $\chem{B_{12}}$

E. Z. Kurmaev; A. Moewes; L. Ouyang; L. Randaccio; P. Rulis; W. Y. Ching; M. Bach; M. Neumann

doi:doi:10.1209/epl/i2003-00390-9

DOI: 10.1209/epl/i2003-00390-9
Europhys. Lett., 62 (4) , pp. 582-587 (2003)

The electronic structure and chemical bonding of vitamin $\chem{B_{12}}$

E. Z. Kurmaev¹, A. Moewes², L. Ouyang³, L. Randaccio⁴, P. Rulis³, W. Y. Ching³, M. Bach⁵ and M. Neumann⁵

¹ Institute of Metal Physics, Russian Academy of Science-Ural Division 620219 Yekaterinburg GSP-170, Russia
² Department of Physics and Engineering Physics, University of Saskatchewan 116 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
³ Department of Physics, University of Missouri-Kansas City Kansas City, MO 64110, USA
⁴ Center of Excellence in Biocystallography, Dipartimento di Scienze Chimiche Università di Trieste - 34127 Trieste, Italy
⁵ Universität Osnabrück, Fachbereich Physik - D-49069 Osnabrück, Germany

(Received 8 August 2002; accepted in final form 13 March 2003)

Abstract
The electronic structure and chemical bonding of vitamin $\chem{B_{12}}$ (cyanocobalamin) and $\chem{B_{12}}$ -derivative (methylcobalamin) are studied by means of X-ray emission (XES) and photoelectron (XPS) spectroscopy. The obtained results are compared with ab initio electronic structure calculations using the orthogonalized linear combination of the atomic orbital method (OLCAO). We show that the chemical bonding in vitamin $\chem{B_{12}}$ is characterized by the strong $\chem{Co}$ - $\chem{C}$ bond and relatively weak axial $\chem{Co}$ - $\chem{N}$ bond. It is further confirmed that the $\chem{Co}$ - $\chem{C}$ bond in cyanocobalamin is stronger than that of methylcobalamin resulting in their different biological activity.

PACS
78.70.En - X-ray emission spectra and fluorescence.
87.64.Fb - EXAFS spectroscopy.
87.15.By - Structure and bonding.

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