BINDING OF DIOXYGEN IN A PICKET-FENCE PORPHYRIN COMPLEX OF IRON - A THEORETICAL QM MM STUDY/

The hybrid quantum mechanics/molecular mechanics method IMOMM is appli ed to the calculation of the structure of the oxygenated picket-fence porphyrin complex of iron Fe(TpivPP)(1-MeIm)(O-2), with results in goo d agreement with available X-ray data. An investigation on the role of the picket-fence substituents in the binding of dioxygen through comp arison with additional calculations on a system with the ''naked'' por phyrin complex Fe(P)(1-MeIm)(O-2) shows that the presence of the amide groups of the picket-fences contribute to the binding with ca. 5 kcal mol(-1). The largest contribution to this stabilization is found to c orrespond to an O ... H(N) interaction.