It can be seen that the phenyl groups in molecules are conjugated with the pyrazoline ring and create conjugated π system. The dihedral angles between phenyl and pyrazole rings of the AB1 and AB2connected with the N\(-\)C bonds [N\(-\)C: 1.419 for AB1 1.420 for AB2 ] are 41.7 and 64.0, respectively. The discrepancy between the dihedral angles are attributed to the introduction of the sterically hindered nitro (NO2) groups which decreases the planarity of the molecular structure in solid phase. The internal rotations of theAB1 are restricted by strong short interactions [Br2\(\cdots\) H7: 2.96 \(\mathring{\mathrm{A}}\)] while that ofAB2 are provided by intramolecular N\(-\)O\(\cdots\) π interactions ( Table 3). Pyrazole and phenyl rings of the AB1make the angle of 16.8(4)\(\ \) and 24.9(3)\(\ \) with the molecule plane, respectively whereas for AB2, these angles are 40.6(2)\(\ \) and 23.34(2)\(\ \) Since there are no nonclassical hydrogen bonds and X\(-\)Y\(\cdots\) ring interactions in the crystal structure of compoundAB1, the only strong intermolecular \(\pi\cdots\pi\) stacking interactions and short interactions are responsible for its rigid structure in aggregation or packing phase. However, the moleculeAB2 has intermolecular nonclassical hydrogen bonds, X\(-\)Y\(\cdots\) ring interactions and strong \(\pi\cdots\pi\) stacking interactions in solid phase due to the presence of the electron withdrawing groups (NO₂) connected to phenyl ring in its terminal side (Table 3).

Table 3. Molecular noncovalent interactions geometry of the molecules (Å, °).