X-ray single crystal investigations of magnesium phthalocyanine. The 4+1 coordination of the Mg ion and its consequence

Crystals of magnesium phthalocyanine were obtained directly from the reaction of powdered magnesium with 1,2-dicyanobenzene at 270 degreesC. The crystals of MgPc under ambient atmosphere as well as in the atmosphere of pure O-2 or N-2 are unstable and transform to (MgPc)(2)O-2 and/or (MgPc)(2)N-2. The formation process Of (MgPc)(2)X-2 (X = 0, N) is reversible and strongly depends on the temperature. Single crystal X-ray investigations at different temperatures of magnesium phthalocyanine show that the Mg-Pc molecule is not planar. The magnesium cation is significantly deviated from the N-4-isoindole plane. The deviation of the Mg cation from the N-4-plane increases with decrease of temperature. The intermolecular Mg . . .N-azamethine interactions lead to the formation of the dimers - (MgPc)(2) -which are stabilised by 4 + 1 coordination of the Mg ions. The dimers of magnesium phthalocyanine are statistically disordered in the crystal. The presence of the dimers of magnesium phthalocyanine has been correlated with its stability. (C) 2001 Elsevier Science Ltd. All rights reserved.