Emergence of chirality and structural complexity in single crystals at the molecular and morphological levels

Naturally occurring single crystals having a multidomain morphology are a counterintuitive phenonomon: the macroscopic appearance is expected to follow the symmetry of the unit cell. Growing such crystals in the lab is a great challenge, especially from organic molecules. We achieve here uniform metallo-organic crystals that exhibit single crystallinity with apparently distinct domains and chirality. The chirality is present at both the molecular and macroscopic levels, although only achiral elements are used. “Yo-yo”-like structures having opposite helical handedness evolve from initially formed seemingly achiral cylinders. This non-polyhedral morphology coexists with a continuous coordination network forming homochiral channels. This work sheds light on the enigmatic aspects of fascinating crystallization processes occurring in biological mineralization. Our findings open up opportunities to generate new porous and hierarchical chiral materials.

* The nitrate counter ions have not been observed by X-ray analysis, but have been included in the formula for completeness. These ions have been observed spectroscopically by FT-IR ( Supplementary Fig. 13) ** Calculated using the "contact surface", obtained from the Mercury CSD 3.10.2 program, employing a spherical probe of 1.2 Å radius. Table 2. Single crystal X-ray data for entire yo-yo-like crystals. Crystal data and structure refinement parameters for the 3 intact yo-yo-like crystals indicated in Figure 4 with orange, green and grey symbols, respectively.  (7) 0.01 (6) * The nitrate counter ions have not been observed by X-ray analysis, but have been included in the formula for completeness. These ions have been observed spectroscopically by FT-IR ( Supplementary Fig. 13). * Calculated using the "contact surface", obtained from the Mercury CSD 3.10.2 program, employing a spherical probe of 1.2 Å radius.

Supplementary
Supplementary Table 3. Single crystal X-ray data for half yo-yo-like crystal. Crystal data and structure refinement parameters for the two subunits of the yo-yo-like crystals indicated in Figure 4 as blue symbols (A and B).  (7) 0.07 (7) * The nitrate counter ions have not been observed by X-ray analysis, but have been included in the formula for completeness. These ions have been observed spectroscopically by FT-IR ( Supplementary Fig. 13). * Calculated using the "contact surface", obtained from the Mercury CSD 3.10.2 program, employing a spherical probe of 1.2 Å radius.
Supplementary Table 4. Single crystal X-ray data for half yo-yo-like crystal. Crystal data and structure refinement parameters for the two subunits of the yo-yo-like crystals indicated in Figure 4 as pink symbols (A and B).  (7) * The nitrate counter ions have not been observed by X-ray analysis, but have been included in the formula for completeness. These ions have been observed spectroscopically by FT-IR ( Supplementary Fig. 13). * Calculated using the "contact surface", obtained from the Mercury CSD 3.10.2 program, employing a spherical probe of 1.2 Å radius. Table 5. Single crystal X-ray data for half yo-yo-like crystal. Crystal data and structure refinement parameters for the two subunits of the "yo-yo"-like crystals indicated in Figure 4 as yellow symbols (A and B). 0.319 and -0.213 * The nitrate counter ions have not been observed by X-ray analysis, but have been included in the formula for completeness. These ions have been observed spectroscopically by FT-IR ( Supplementary Fig. 13). ** Calculated using the "contact surface", obtained from the Mercury CSD 3.10.2 program, employing a spherical probe of 1.2 Å radius.

Supplementary Note 1. Single crystal X-ray data and Flack parameter analysis.
Full data sets for each crystal including Friedel pair reflections were collected. The Friedel pairs were not merged. The full least square refinement was carried out until convergence for each structure using SHELXL 2016/4. 1 The absolute structure of each completed structure was determined as being correct for that structure by having a Flack parameter close to 0. The Flack parameters were determined using SHELXL [(I+)-(I-)]/[(I+)+(I-)] 2 and were taken from the cif files. Such experimental Flack parameters indicated the enantiopurity of each crystal but not the absolute chiral configurations. The absolute chiral configurations for each crystal vs other crystals were done by doing a Cross-Flack refinement. For each pair of structures to be compared (here named crystals 1 and 2), the reflections (hkl) file of crystal 1 was refined until convergence against the coordinate model (xyz) of crystal 2. The resulting Flack parameter x was calculated in SHELXL 2016/4 2 and taken from the cif file. The files were then reversed and the coordinate file (xyz) of crystal 1 was refined to convergence against the reflections (hkl) file of crystal 2. In cases where the Flack parameter was close to 0, it was determined that the relative absolute configuration of the two crystals was the same. In cases where the Flack parameter was close to 1 it was determined that the two crystals were of opposite absolute configuration. These Cross-Flack refinements were done for all possible combinations of crystal structures presented in this paper and are given in the table in Figure 4D.

Supplementary Note 2. Elemental composition.
The sample contains after 2 days of ageing both the yo-yo-like structures and organic rods. The bulk elemental composition (weight %) from duplicate elemental analysis is C,29.35;H,5.72;N,3.12;Cl,1.18;Cu,2.89. The amount of oxygen is estimated as 57.74%. This composition indicates a formula of C 54.4 H 127 N 5 Cu 1 Cl 0 . 7 O 80 . Quantitative analysis of TEM-EDX data was performed on a microtome sliced lamella of a yo-yolike crystal ( Supplementary Fig. 11). A sliced sample was used to avoid possible artifacts due to surface residues or reabsorption of the signal from the low energy carbon X-rays. These TEM-EDX measurements indicate a molecular formula of C 41 N 2.2 Cu 1 O 5.9. Hydrogen atoms cannot be detected by this method. We used a ratio of Cu(NO 3 ) 2 . H 2 O:TPEPA = 2:1, whereas the crystallographic studies of the yo-yo-like structures reveal a ratio of 1:1. No copper ions are observed in the crystallographic structure of the organic rods. This data suggest that an excess of copper ions is present in the channels of the samples. FT-IR measurements show a band at 1382 cm -1 indicative of the presence of nitrate anions ( Supplementary Fig. 13).