Structural Parameters, NLO, HOMO, LUMO, MEP, Chemical Reactivity Descriptors, Mulliken-NPA, Thermodynamic Functions, Hirshfeld Surface Analysis and Molecular Docking of 1,3-Bis(4-methylphenyl)triazine

In the current study, the molecular geometry, electronic characteristics, nonlinear optical (NLO) properties, and potential biological activity of 1,3-bis(4-methylphenyl)triazene (I) were investigated by a combination of experimental crystallographic data and density functional theory (DFT) calculations at the B3LYP/6-311++G(d,p) level. The optimized molecular geometry was in very good agreement with experimental X-ray data, with a low root-mean-square deviation (RMSD) of 0.106 Å, verifying the computational model. The molecule demonstrated high NLO activity, possessing a first-order hyperpolarizability roughly seven times larger than that of urea, and potential application in optoelectronic and photonic devices. Frontier molecular orbital (FMO) calculation demonstrated HOMO–LUMO energy gap of 5.6015 eV in the gas-phase indicating kinetic stability, and solvent-phase calculation indicated higher reactivity and polarity at high-dielectric conditions. Global reactivity descriptors and molecular electrostatic potential (MEP) mapping identified key electrophilic and nucleophilic sites, with implications for the charge distribution of the molecule and probable modes of interaction. Mulliken and natural population analyses (NPA) also revealed electronic behavior, NPA providing more chemically meaningful charge partitioning. Thermodynamic properties -entropy, enthalpy, and heat capacity- exhibited smooth temperature dependence, which established the thermal stability of the compound. Hirshfeld surface and 2D fingerprint plots of the crystal structure highlighted the dominant role played by van der Waals interactions in crystal packing. Molecular docking studies with the HER2 receptor (PDB ID: 3PP0) showed good binding affinity (-9.8 k cal mol⁻¹) with the aid of supporting hydrogen bonding and hydrophobic interactions with prominent amino acid residues, which reflected potential anticancer activity. Combined, the findings emphasize the exciting multifunctionality of I, whose potential uses range from materials science to being a lead scaffold in drug design, particularly for HER2-targeted anticancer drugs.