Crystal structure prediction of organic materials: Tests on the 1,4-diketo-3,6-diphenylpyrrolo(3,4-c)pyrrole and 1,4-diketo-3,6-bis(4′-dipyridyl)-pyrrolo-[3,4-c]pyrrole

The crystal structures of a yellowish-red pigment, 1,4-diketo-3,6-diphenylpyrrolo(3,4-c)pyrrole (DPP), and its derivative with high proton affinity, 1,4-diketo-3,6-bis(4′-dipyridyl)-pyrrolo-[3,4-c]pyrrole(DPPP), were predicted using Polymorph Predictor in Materials Studio 4.4. The possible structures were generated using Monte Carlo method and they were minimized with COMPASS and Dreiding forcefields. Among the predicted structures with the space groups same as those of the experimental X-ray crystal structures, structures fitting best to the experimental structures were searched. The resulting structures are in good agreement with the experimental structures showing that Monte Carlo simulated annealing is an efficient method for predicting crystal structures of DPP derivatives.