On polymorphic and non-polymorphic conversions of phthalocyanines

The X-ray and IR spectra of metal-free phthalocyanine show that the x-form of H2Pc is β-Pc. X-ray measurements of the β-form of MgPc reveal that alteration to the so-called α-form of MgPc occurs in air. Continued cycling of the sample between vacuum and air demonstrated the reversibility of this process. It has been concluded, that, in general, α-forms of M(II)Pc are not pure phthalocyanines, but are complexes of M(II)Pc with N2 and O2 molecules.