Abstract
An azo–azomethine–pyrazole hybrid, namely, 2-({[3-
tert
-butyl-1-(4-nitrophenyl)-1
H
-pyrazol-5-yl]imino}methyl)-4-[(4-methylphenyl)diazenyl]phenol, C
27
H
26
N
6
O
3
, crystallizes as an extended donor–π–acceptor system that combines azo, azomethine and pyrazole fragments within an almost coplanar conjugated framework. Single-crystal XRD revealed two crystallographically independent molecules (
M
1 and
M
2) in the asymmetric unit (
Z
′ = 2), with small conformational differences arising mainly from the orientation variations of the peripheral substituents. In both molecules, an intramolecular O—H...N(imine) hydrogen bond generates an
S
(6) motif that reinforces molecular planarity and π-electron delocalization. The crystal packing is dominated by heterogeneous
M
1...
M
2 contacts, whereas the homologous
M
1...
M
1 and
M
2...
M
2 interactions are comparatively less effective. C—H...O and C—H...N hydrogen bonds, complemented by π-related contacts, assemble the molecules into a three-dimensional supramolecular architecture. The Hirshfeld surface analysis identifies H...H, C...H/H...C, O...H/H...O and N...H/H...N contacts as the principal contributors to the intermolecular organization. A Quantum Theory of Atoms in Molecules (QTAIM) analysis confirmed the intramolecular O—H...N(imine) interaction through the corresponding bond critical point and associated topological descriptors and also confirmed that a secondary intramolecular C—H...N(imine) contact forms a nonplanar
S
(6) motif. The FT–IR,
1
H NMR and mass spectrometric data support the proposed molecular structure. The combined crystallographic, Hirshfeld surface and QTAIM analyses demonstrate the co-operative influence of hydrogen bonding and weak noncovalent interactions on the conformational stabilization and supramolecular assembly of this conjugated azo–azomethine–pyrazole system.