N-DONOR COMPLEX FORMATION AND POLYMORPHIC TRANSFORMATION OF ZINC PHTHALOCYANINE IN ORGANIC SUSPENSION MEDIA

The polymorphic transformation process of zinc phthalocyanine dispersed in various organic suspension media was studied by X-ray diffraction, differential thermal analysis, and infrared absorption spectroscopy. Strong n-donor solvents, such as heterocyclic and normal amines, dioxane, and dimethyl sulfoxide, were found to form stoichiometric molecular compounds with zinc phthalocyanine in the solid phase. The compositions were determined by weight-loss measurements and from the thermal behavior of the addition compounds as observed by DTA analysis and X-ray diffraction. The decomposition temperature ranged from 70 to 240°, above which the crystallites were converted into the β form. Solvents other than n donors caused the a form to undergo an ordinary transformation into the β form. The process was found to be consecutive and two different new polymorphs (χ and θ) appeared as the intermediate phases, depending upon whether the suspension media consisted of electron donors or electron acceptors. The infrared absorption spectra assigned to the fundamental bands of the adduct molecules showed large shifts toward higher frequencies, which suggested that the coordination in the complexes could be interpreted in terms of a charge-transfer mechanism.