Due to its poor solubility, we were unable to crystallize TPyP from solvent. We therefore sublimed TPyP under vacuum at 450 °C to afford a solvent-free structure, TPyP-α, which crystallized in the monoclinic space group P21/n (SI, Figure ). TPyP-α is reproduced accurately by the predicted global minimum energy crystal structure, 3 (Figure , SI, Figure ) and features close-packed, interdigitated, columnar stacks of TPyP molecules, which are packed 3.95 Å apart along the crystallographic a axis.