In this work, the asymmetric ligands [1-(phenyl)-3-(2-nitro-4-methylphenyl)]triazene (1), [1-(4-methylphenyl)-3-(2-nitro-4-methylphenyl)]triazene (2), [1-(4-ethylphenyl)-3-(2-nitro-4-methylphenyl)]triazene (3) and [1-(4-ethoxyphenyl)-3-(2-nitro-4-methylphenyl)]triazene (4), were synthesized. The reaction of the ligand (3) with HgCl₂ in methanol resulted in the formation of the [HgL₂] complex, (5). All compounds were characterized by means of CHN analysis, FT-IR, ¹H NMR, ¹³C NMR spectroscopy. In addition, the crystal structures of the ligands (2) to (4) were investigated by single crystal X-ray analysis. In the solid state, all ligands exhibited trans conformation about the –N=N– double bond. The Hg^II complex (5) crystallized in monoclinic system with 𝐶2/𝑐 space group. The triazene ligand was found to be deprotonated prior to coordination and acts as monodentate ligand. The Hg^II which lies on inversion center (site symmetry $\bar{1}$), is surrounded by two N atoms from L ligands forming a linear geometry. The other two Hg–N bonds are relatively longer and can only be regarded as weak secondary bonds. Also, Hg-𝜂³-arene 𝜋-interactions are present in this compound. Hydrogen bonds, 𝜋 · · · 𝜋 and C–H· · · 𝜋 stacking interactions help in the stabilization of the resulted frameworks. These C–H· · · 𝜋 edge-to-face interactions are present with H· · · 𝜋 distance of 3.00 Å.