The structure and properties of a sheathed, low reactivity silicon phthalocyanine and the potential for still more inert phthalocyanines

The structure of a silicon phthalocyanine having a sheath composed of eight 1,4-isobutoxy, four bidentate 2,3-dibenzobarreleno substituents, and two trans- heptacyclopentylpentacyclooctasiloxy ligands has been determined by X-ray crystallography. The macrocycle in this compound is nearly completely covered by its sheath, but there is a channel in it which is large enough to give small diatomic molecules easy access to the macrocycle. In solution, transient channels exist in the sheath because of molecular vibrations. The structure of the compound also has been determined by a PM6 semi-empirical calculation. Except for one understandable difference, the results from this calculation are in good agreement with the results from the crystal determination. The van der Waals volume of the molecule has been determined from both the crystal and PM6 data by a Monte Carlo method. The amount of steric hindrance present in analogs of the compound in which its isobutoxy substituents are replaced by other alkoxy groups has been examined through calculations based on van der Waals volumes. Possible analogs of this sheathed molecule are suggested in which the sheath may be impenetrable to even small molecules and thus that are highly resistant to attack.