Table 1.
Distances between the heavy atoms involved in the formation of conventional hydrogen bonds in [CRB + MLE] (1:1). Experiment (Exp.) vs. theoretical values. Computations at different levels of approximation with fixed unit cell parameters (AtomOnly) and full unit cell relaxation (FullOpt). The FullOpt values are given in parentheses. The units are Å. The relative change in the volume of the crystallographic cell ∆V is given in the last line.
| Fragment (a) | Exp. | Computations | ||||
|---|---|---|---|---|---|---|
| PBE-D3/6-31G(d,p) | B3LYP/6-31G(d,p) | B3LYP-D2/6-31G(d,p) | B3LYP-D3/6-31G(d,p) | PBE-D3/PW (b) | ||
| O24–H24···O21 (intra-) | 2.442 | 2.462 (2.481) | 2.446 (2.399) | 2.468 (2.433) | 2.457 (2.443) | 2.453 (2.456) |
| N1–H1···O21 | 2.685 | 2.662 (2.700) | 2.665 (2.622) | 2.700 (2.640) | 2.680 (2.641) | 2.675 (2.670) |
| N3–H3···O22 | 2.761 | 2.735 (2.798) | 2.768 (2.718) | 2.762 (2.746) | 2.757 (2.745) | 2.741 (2.744) |
| N2–H2···O23 | 2.756 | 2.701 (2.665) | 2.714 (2.684) | 2.750 (2.681) | 2.701 (2.677) | |
| ∆V = (Vexp − Vtheor)/Vexp (%) | 3.1 | 6.8 | −9.2 | 13.3 | 9.4 | <−0.1 |
(a) Atomic numbering is given in Figure 2; (b) PW stands for the plane-wave basis set with a cut-off energy of 100 Ry and PAW pseudopotentials.