Table 2. C4–NH–C5–C6 Torsional Angle (deg) Values in TFM for Single-Crystal X-ray Diffraction Structures and Those Obtained after DFT-D (CASTEP) Geometry Optimization.
| C4–NH–C5–C6 torsional angle |
|||
|---|---|---|---|
| structure | X-ray data | DFT-D (opt all)a | DFT-D (opt all + cell)b |
| TFMLT (molecule A) | 4.5 | 3.4 | 4.2 |
| TFMLT (molecule B) | 31.9 | 29.1 | 29.3 |
| TFMRT (lower A occupancy sites)c | –7.8 | 5.1 | 4.2 |
| TFMRT (higher B occupancy sites)c | 28.6 | 4.7 | 5.7 |
a
DFT-D geometry optimization of all atomic positions with the unit cell parameters fixed to those determined by X-ray diffraction.
b
DFT-D geometry optimization of all atomic positions and allowing the unit cell parameters to vary (see Table S1 in the Supporting Information)
c
The DFT calculations for the lower A and higher B occupancy sites of TFMRT were performed for two separate systems where the starting unit cell contains the experimental A or B sites only.