Ab-initio X-ray powder structure analysis of two polymorphs of dihydroxysilicon phthalocyanine

Article abstract of DOI:10.1246/bcsj.72.2203

This paper reports on the synthesis and ab-initio X-ray powder structure determination of two polymorphs of [Si(OH)₂Pc], where Pc = phtalocyaninato. We found that one of the polymorphs (Phase II) shows high sensitivity for an electrophotographic photoreceptor, but that the other (Phase I) doesn't have photosensitivity. The difference in the sensitivity depends on only the crystal structures. This material has not been able to be grown to a single crystal with sufficient size for single crystal X-ray analysis, but it is very important to determine the crystal structures of the two polymorphs for understanding the mechanism of the performance of the electrophotographic photoreceptor. In this work we carried out ab-initio X-ray powder structure analysis. The compound crystallizes in space group P1 (Phase I), Z = 1 with unit-cell parameters of a = 12.992(1), b = 7.2830(8), c = 6.861(1) A, α = 104.413(7)°, β = 101.757(8)°, γ = 96.973(6)°and in space group P2₁/n (Phase II), Z = 2 with unit-cell parameters of a = 12.7494(5), b = 14.5778(6), c = 6.7727(3) A, β = 94.353(2)°. Both phases have symmetry center in the molecules (on Si atom) and intermolecular hydrogen bonds (O-H ··· N). These hydrogen bond modes of Phase I and Phase II are the same. The main difference in packings was revealed between the crystals: Phase II crystal has the herringbone structure, while in Phase I all molecules form the parallel stack columns.