X-Ray Diffraction Study of Crystal Structure and Thin Films of Chromium(II) Phthalocyaninate

Abstract

Crystal structure of Cr(II) phthalocyaninate (CrPc) was determined by means of single-crystal X-ray diffraction. It was shown that after vacuum sublimation CrPc crystallized as a β-polymorph, which was isostructural to β-polymorphs of other metal phthalocyanines. When deposited onto glass substrate by organic molecular beam deposition, CrPc formed thin films with strong preferred orientation, consisting of α-polymorph. It was shown that both β-CrPc powder and α-CrPc films were unstable in air and transformed to Cr(OH)Pc. X-Ray diffraction (XRD) studies showed that β-CrPc polycrystalline powder after storage in air (relative humidity 20 %) began to exhibit the first signs of degradation already in 1 hour, while the first changes in XRD patterns of α-CrPc films became noticeable only after a few days. Annealing of α-CrPc films at 250 °C in air at a relative humidity of 70 % leads to their faster conversion to Cr(OH)Pc, and the resulting films have a high degree of crystallinity.