<p>Extended π-conjugated aromatic systems exhibit characteristic crystal-packing motifs governed by the interplay of π-π stacking, C-H···π, and weak hydrogen-bonding interactions. To probe the extent by which appended functional groups influence, disrupt, or reinforce the established packing hierarchy, characteristic of extended polycyclic heteroaromatic frameworks, a series of dibenzo[a, c]phenazine derivatives-, halogenated (12-bromo-1-chloro), and two nitro-substituted analogues (11-nitro and 10-nitro) along with the unsubstituted analogue were synthesized. The compounds were characterized using ¹H NMR, IR spectroscopy, differential scanning calorimetry, and single-crystal X-ray diffraction techniques. Hirshfeld surface analysis, and lattice energy calculations were employed to identify and quantify the dominant noncovalent contacts. All derivatives exhibit π-π stacking as the principal stabilizing feature, accompanied by C-H···π and C-H···N interactions, while the halogenated structure additionally displays C-H···Cl and C-Br···N halogen bonded contacts. The nitro-substituted derivatives engage both the oxygen atoms of the -NO₂ group in distinct C-H···O interactions. The results demonstrate that functional group modification modulates secondary interaction patterns while preserving the primary π- π stacking arrangement characteristic of extended aromatic systems.</p>