Comparative studies of photophysical and photochemical properties of solketal substituted platinum(II) and zinc(II) phthalocyanine sets

9 – Mass Spectra of Porphyrins and Related Compounds

Mass spectrometric studies of the composition of the gaseous phase under solid compounds of free phthalocyanine (H2Pc) and its complexes with aluminium (AlClPc, AlFPc, (AlPc)2O) and copper (CuPc) were performed in the temperature range up to 700 °C. It has been shown that the phthalocyanines sublime in the form of monomers, excluding one aluminium complex. All phthalocyanines under investigation sublime without thermal decomposition until 700 °C. The vapour pressure of these phthalocyanines was determined as a function of temperature by the Knudsen effusion method, in which the rate of effusion of the equilibrium vapour through a small orifice was measured. The thermodynamic parameters of the sublimation process for phthalocyanies were calculated.

Vapour pressure of some phthalocyanines

PhthalocyaninesPc−Me(III)X andPc−Me(V)X3 were obtained by reacting anhydrous metal halides with phthalodinitrile and di-lithium-phthalocyanine, resp. A phthalocyanine containing niobium(V) was prepared for the first time. Mass spectrometric investigation of the products formed show the molecular ion in the case of chloro-aluminum-, chloro-indium- and tribromo-niobium-phthalocyanine. The mass spectra of chloro-scandium-, chloro-yttrium- and tribromo-tantalum-phthalocyanine showed neither peaks of the molecular mass nor metal containing fragments of the phthalocyanine structure. Mass spectrometric results seem to depend critically on the purity of the compounds employed.

Massenspektrometrische Untersuchungen von PhthalocyaninenPc—MeXn

Mass spectr of phthalocyanines are readily obtainable by field desorption mass spectrometry. Molecular ions are normally the base peaks in the spectra and minimal fragmentation is observed. The technique provides a rapid method for the qualitative exmination of mixtures of phthalocyanines.

Field desorption mass spectra of phthalocyanines

The mass spectra of some chlorinated copper phthalocyanines have already been reported. These observations suggested that at least two processes were occurring, namely electron-impact-induced dissociation and thermal depolymerization. The combined effect of these yielded the mass spectrum that comprised the parent molecular ion, a composite ion which represents one quarter of the molecule with a copper atom attached, and halogenated phthalonitrile ions together with some fragments corresponding to halogen atoms. Even if the parent molecular ion is absent, as happens with highly substituted compounds, a partial structure may be deduced from a consideration of the phthalonitrile ions produced by the depolymerization. Each molecule of phthalocyanine depolymerizes to yield four phthalonitrile molecules.

H. C. Hill

Papers

Electron Impact and Molecular Dissociation—Part XVII. Mass Spectra of Some Halogenated Copper Phthalocyanines: