The powder X-ray diffraction lines of the three polymorphs of compound A are significantly distinct to permit characterization of the bulk material in each case (Fig. S8), as well as to monitor phase transitions. The peaks of Form I appear at 2θ 9.89, 10.84, 13.22, 13.66, 15.66°, for Form II at 7.08, 8.94, 11.58, 12.82, 14.19°, and Form III at 9.21, 12.32, 13.75°.