Theoretical/computational analysis of structural, electronic and reactivity properties of caffeine

Based on the significant role of caffeine in human life and the environment, a robust computational analysis was initiated to ascertain the role of theoretical computation in ascertaining the behaviour of caffeine. This study presents a comprehensive quantum chemical investigation of the structural , electrostatic, and electronic properties of caffeine using Density Functional Theory (DFT) calculations performed with the DMol³ module at the B3LYP/DND level of theory. Full geometry optimization was achieved, and electronic structure analyses and computation were carried out to ascertain the molecular stability, reactivity descriptors, electrostatic characteristics, and corrosion inhibition potential of caffeine. The optimized structure exhibited good electronic convergence with a total energy of −719.660019 Ha and binding energy of −45.462865 Ha, which confirmed the stability of the molecular system. Frontier molecular orbital (FMO) analysis revealed a Highest Occupied Molecular Orbital (HOMO) energy of −6.094 eV and a Lowest Unoccupied Molecular Orbital (LUMO) energy of −0.978 eV, while the energy gap was 5.116 eV, indicative of high kinetic stability and moderate chemical reactivity. The calculated dipole moment of 1.55 D confirms that caffeine is polar in nature and can participate in intermolecular interactions. Density of states (DOS) analysis showed a dense distribution of occupied electronic states below the Fermi level with a clear band gap region, which confirmed the insulating molecular character of caffeine. Global reactivity descriptors derived from frontier orbital energies yielded a chemical hardness corresponding to a back-donation energy of 0.1123 eV, suggesting weak π-acceptor capability. The calculated work function of 3.692 eV indicated favourable electron exchange and adsorption characteristics, supporting the suitability of caffeine as a potential environmentally friendly corrosion inhibitor. Electrostatic energy contributions further confirmed charge localization around oxygen and nitrogen heteroatoms, identifying them as primary reactive centers. The computational results provided detailed insight into the electronic structure, stability, and interaction potential of caffeine and provide evidence regarding its applicability in molecular recognition and corrosion inhibition systems.