To compare our model structures to experimental values, Npe:TCNB crystals were synthesized and spectroscopically characterized. Single crystals of Npe:TCNB were grown by slow evaporation of a 1:1 molar ratio of TCNB and Npe dissolved in a 1:1 (vol.) DMF/MeCN mixture, resulting in yellow blade-like crystals suitable for single-crystal X-ray diffraction (SCXRD). Analysis by SCXRD determined that the Npe:TCNB co-crystal, in contrast to the previously reported triclinic structure, crystallizes with a 1:1 ratio of TCNB to Npe in the monoclinic space group P21/c with a = 6.73, b = 36.66, and c = 9.51 Å(β = 106•). Although the single-crystal XRD measurement was performed at 100 K, there is still a large amount of disorder around the pyridine moiety of Npe, which appears to be "rocking" and generating an additional conformation of the pyridine ring that is >45• out of the plane with respect to the other occupied pyridine site. The expanded structure reveals that there is a ππ stacking interaction between the naphthalene moiety of the Npe and the benzene ring of the TCNB molecule with a distance of 3.375 Å. The pyridine of Npe interacts with other Npe-pyridines in adjacent layers with a centroid-centroid distance of 3.9 -4.9 Å, Figure . The crystal structure shows no evidence of interaction between the Npe pyridine moiety and TCNB. Further details on the crystal structure data are given in ESI Section 3.