A final confirmation that the determined structure is plausible can be made by comparison with the known fluorinated and chlorinated derivative crystal structures (2F-EPI and 2Cl-EPI, respectively).11 A first visual comparison can be made by overlaying the conjugated backbone of a molecule in the EPI structure with those from the derivative structures and then generating the surrounding molecules of both structures to observe if there is an agreement in the extended crystal packing (see Fig. S4 in the ESI†). From this analysis, it can be seen that there is an excellent agreement between the packing in the EPI structure and that of the fluorinated derivative (2F-EPI), this is an encouraging indicator with regards to the chosen EPI structure. The similarity in the structures is perhaps unsurprising given the similar unit cell parameters (there is only a small reduction in volume of the EPI unit cell compared with the fluorinated derivative, most likely arising from the replacement of fluorine atoms with smaller hydrogen atoms). It should be noted here that the structures of the derivatives were not used as an input or reference at any point during the MD and DFT simulations, and were only studied once a final structure for EPI in the 300 K thin film had been chosen.