Polymorph
prediction of organic pigments
N. Panina, R. van de Ven, P. Verwer,
H. Meekes , E. Vlieg and G.
Deroover
Dyes and Pigments 79 Issue 2 (2008)
183-192
Abstract
The crystal structure of several
industrially important organic
pigments namely C.I. Pigment Violet 23, C.I. Pigment Red 202 and C.I.
Pigment Yellow 139 were predicted using the Cerius2 Polymorph Predictor
in combination with XRPD patterns. After generation and energy
minimisation of the candidate structures for each pigment, their
calculated powder patterns were compared with those obtained
experimentally using X-ray diffraction. The structures which best
fitted the experimental powder patterns were regarded as possible
structures of the compound; finally, a rigid body Rietveld refinement
was performed to validate the choice of the structure. The structure of
C.I. Pigment Violet 23 has not previously been published while the
predicted structures of C.I. Pigment Red 202 and C.I. Pigment Yellow
139 were in accordance with the published structures. The work
demonstrates that pigment crystal structure can be predicted using a
low quality X-ray powder diffraction pattern.