An Inclusion Complex Containing the Dioxygen Molecule and an Organic Guest Molecule Cohabiting Within a Vaulted Cobalt(II) Cyclidene Host—A Rare Kind of Ternary Complex

A credible model of the ternary complex of cytochrome P450 has been demonstrated with use of NMR spin lattice relaxation determinations on guest protons in the presence of the dioxygen adduct of a vaulted cyclidene-cobalt(II) host. Hydrophobic forces produce regiospecific binding of the 1-butanol guest within the cavity of the vaulted cyclidene cobalt complex while the metal center is simultaneously coordinated to dioxygen. The ternary complex is formulated as [{(vaulted cyclidene cobalt(II)}-dioxygen-guest]. The spin density localized on the coordinated dioxygen acts as the paramagnetic center, and results obtained at two spectrometer frequencies yield the same calculated distances. ESR and visible spectral measurements establish the stability and reversibility of the dioxygen adduct under the conditions used in the NMR studies. Distance determinations made with the deoxygenated form of the cobalt(II) complex are the same, within experimental error, as those found with the analogous copper(II) complexes of the ligands.