Npe:TCNB co-crystals were synthesized by dissolution of 0.5 mmol TCNB and 0.5 mmol Npe in a 20 mL vial with 6 mL of a 1:1 DMF:MeCN solvent. Once fully dissolved, the yellow solution was allowed to slowly evaporate forming broad needle-like crystals. A bulk powder form of the Npe:TCNB co-crystals can be formed by mixing two separate TCNB and Npe solutions in pure MeCN.