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 reacti on of powdered magnesium with 1,2-dicyanobenzene at 270 degreesC. The cryst als 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. T he formation process Of (MgPc)(2)X-2 (X = 0, N) is reversible and strongly depends on the temperature. Single crystal X-ray investigations at differen t temperatures of magnesium phthalocyanine show that the Mg-Pc molecule is not planar. The magnesium cation is significantly deviated from the N-4-iso indole plane. The deviation of the Mg cation from the N-4-plane increases w ith decrease of temperature. The intermolecular Mg . . .N-azamethine intera ctions lead to the formation of the dimers - (MgPc)(2) -which are stabilise d by 4 + 1 coordination of the Mg ions. The dimers of magnesium phthalocyan ine are statistically disordered in the crystal. The presence of the dimers of magnesium phthalocyanine has been correlated with its stability. (C) 20 01 Elsevier Science Ltd. All rights reserved.