Context <p>Currently, the study of charge transfer (CT) is significant and has attracted the attention of many researchers. The unique physical and chemical properties and wide range of applications have made charge transfer complexes (CTCs) a popular area of research. Thus, the designation of good components for creating CTCs with stable chemical bonds is very valuable. Quantum theoretical calculations are useful for studying three-centered intramolecular hydrogen bonding in organic molecules. Given that no computational study has been performed on the interaction between <i>p</i>-phenylenediamine (PPD, electron donor) and picric acid (PA, electron acceptor) until now, the UV-visible and IR spectra analysis, parameters such as natural charge (NBO), thermodynamic parameters like interaction energy (<i>∆E°</i>), standard enthalpies (<i>∆H°</i>), entropies (<i>∆S°</i>), Gibbs free energy (<i>∆G°</i>), and frontier molecular orbitals (FMOs) of the hydrogen bond (HB)-CTC were investigated by theoretical calculations (B3LYP method and 6-311G (d, p) basis sets). Molecular properties such as ionization potential (<i>I</i>), electron affinity (<i>A</i>), chemical hardness (<i>η</i>), electronic chemical potential (<i>μ</i>), and electrophilicity (<i>ω</i>) are obtained for the HB-CTC. The investigation focused on understanding intermolecular interactions using the reduced density gradient (RDG) and molecular electrostatic potential (MEP) surfaces. New calculations provide further insight into CTCs, and their potential for new applications is being explored.</p> Methods <p>The DFT calculations were performed using the Gaussian09 program package. The molecular structure and the optimum energy were evaluated using the GaussView 6 program. The electronic properties and spectral characteristics of the complex were analyzed using the B3LYP functional with a 6-311G (d, p) basis set. The thermodynamic functions, interaction energy (<i>ΔE°</i>), enthalpy (<i>ΔH°</i>), entropy (<i>ΔS°</i>), Gibbs free energy (<i>ΔG°</i>), and equilibrium constant were investigated via the vibrational frequency calculations. The vibrational frequencies and corresponding IR spectra were analyzed by determining the harmonic vibrational modes of the optimized geometry. The nature of interactions between CTC components was investigated using parameters MEP and NBO methodologies. To evaluate the charge transfer characteristics of the complexes, the analysis of FMOs (HOMO and LUMO) was performed, and their energy levels of HOMO and LUMO were computed. The theoretical UV-visible spectra were obtained by determining the excited states using time-dependent DFT (TD-DFT). The RDG diagrams were generated using the Multiwfn 3.8 program as a multifunctional wave function analyzer from CHK files.</p> Graphical Abstract <p></p>