The electronic structure and chemical bonding of vitamin

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