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.
Rovira
Carme
C
Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain. crovira@pcb.ub.es
Kunc
Karel
K
Parrinello
Michele
M