Figure 1.
Schematic illustration of the crystal growth methods, the morphology, structure, and packing of TTF-C60 charge-transfer crystals (TCCTs). a) Crystal growth scheme. b) Photograph of TCCTs at the highest concentration of TTF. c,d) SEM images of TCCTs. TTF concentrations are 16.7 and 25 mg mL−1, respectively. The C60 concentration is maintained at 25 mg mL−1. The scale bars for SEM images are 10 μm. e) Crystal structure of C60-TTF-DCB complex in an asymmetric unit without disordered parts. The 50% probability ellipsoids of thermal vibrations are shown. The four C60 molecules have different orientations and these are colored in red, cyan, blue, and purple. The crystallographic nonequivalent molecules are shown in different colors. f) Projection of C60-TTF crystal packing along a axis. g) Double conformation of C60 on the site close to the middle of b cell edge created in crystallographic object-oriented toolkit (COOT).[46,48] The high occupancy (0.81) part is presented as blue line with the 2Fo-Fc electron density map in blue mesh at 2σ level. The low occupancy part (0.19) is presented as green line with Fo-Fc difference electron density map in green mesh at 5σ level. The density map was calculated by SHELXL with the minor part omitted and the major part at 0.81 occupacy fixed. Part (e) was drawn by Mercury,[47] the C60 molecules are shown as ellipsoids, TTF are shown as sticks, and DCBs are shown as wireframe.