3.10. Hirshfeld surface investigation
The Hirshfeld surfaces analysis (3D) and fingerprint plots (2D) are two necessary approaches to evaluate and complete the structural description, both were carried out with Crystal Explorer 3.1 software [67] imported on CIF files. 3D graphics provide a three-dimensional image of intermolecular and intramolecular interactions in crystals, while two-dimensional plots obtained by Hirshfeld surface analysis can identify each type of intermolecular interaction, they are based on thede and di distances to identify the nature of contacts where the term decorresponds to the distance separating the Hirshfeld surface and the nearest atomic nucleus located outside on this surface. As for the termdi , it corresponds to the distance separating the Hirshfeld surface from the nearest atomic nucleus located inside the surface. These two terms are connected with the van der Waals rays by the normalized distance (dnorm ) according to the following equation:
\(d_{\text{norm}}\) =\(\frac{d_{i}-r_{i}^{\text{vdW}}}{r_{i}^{\text{vdW}}}\) +\(\frac{d_{e}-r_{e}^{\text{vdW}}}{r_{e}^{\text{vdW}}}\)
Chloroquin molecular Hirshfeld surfaces were generated using standard high resolution. The dnorm surface (Fig. 10a) is mapped on a color scale varying from -0.388 to 1.402, the ShapeIndex graph (Fig. 10b) located in the color range of -1.0 - 1.0 and Curvedness in the range of -4.0 to 4.0 (Fig. 10c).