Protonation state of the equatorial ligands and dynamics of the OH...O units in a cobaloxime biomimetic.
The protonation state of the dimethylglyoxime ligands in the B(12) coenzyme biomimetic [Co(CCl=CHCl)(dmgH)(2)(py)].CHCl(3) was investigated by using first-principles molecular dynamics. Our simulations at 173 and 300 K reveal that one of the oxime protons remains bonded to a nitroxyl group, while the proton of the second NO...H-ON unit is essentially shared with similar probability between the two oxygen atoms. This reconciles the results of the experimental determination (Jones, P. G.; Yang, L.; Steinborn, D. Acta Cryst. 1996, C52, 2399), showing all N-O distances as equivalent, with the commonly accepted rule that the protonation state of the dimethylglyoxime ligands can be identified by the different N-O distances. Further aspects of the dynamics of the OH...O units, in relation to the occurrence of weak CH...O intermolecular interactions, are analyzed.
Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain. crovira@pcb.ub.es
Carme
C
Rovira
Karel
K
Kunc
Michele
M
Parrinello