Geometry of Cob−L Complexes (L = Ethylenediamine,
Imidazole, and Pyrazine). The geometric structures
of the studied B12 derivatives are depicted in Figure 2, and their
main structural parameters are collected in Table 1.
The comparison of the computed structural parameters with
those obtained with the X-ray diffraction method is possible
only for cobalamins with imidazole and cyano ligands. The
differences between the experimentally determined and the
computed bond lengths for the cobalt−axial ligand bonds for
Cob−Im−/B12−Im− systems are smaller than those for the
Cob−ImH/B12−ImH systems, which may indicate that in
experimental conditions20 Co(III)−Im− is more prevalent. For
cyanocobalamin models, the geometry is well reproduced, once