X-form metal-free phthalocyanine: Crystal structure determination using a combination of high-resolution x-ray powder diffraction and molecular modelling techniques

A combination of high resolution X-ray diffraction and molecular modelling techniques have been used to determine (R_wp = 12.51%) the crystal structure of the X-form of metal-free phthalocyanine. It was found to crystallise in a bimolecular monoclinic unit cell (space group P2₁/a) with lattice parameters a = 10.63, b = 23.15, c = 4.89 Å, ß = 95.98° in a 'herring-bone' molecular packing motif with a smaller angle (50°) than is found in the more stable ß-polymorph (89°).