From lithium batteries to molecular electronics: DFT and QTAIM investigation to reveal the novel capability of NDI-phenyl tetra-nitro as a field effect molecular switch

This study investigates the electronic, structural, and thermoelectric properties of naphthalene diimide-phenyl tetra-nitro as a potential field-effect molecular switch, with an emphasis on how thionation modifies its behavior under external electric fields. Motivated by previous work demonstrating its electrochemical utility in battery systems, we explore the molecule's switching characteristics using quantum chemical calculations based on density functional theory, topological analysis of electron density, and quantum transport theory. Two molecular configurations (pristine and thionated) were modeled between gold electrodes, and their stability was confirmed through vibrational analysis. Application of an electric field revealed that the thionated structure exhibits a reduced energy gap between the highest occupied and lowest unoccupied molecular orbitals, enhanced charge delocalization, and a lower threshold for electronic switching. The tuned system also showed increased dipole moment, polarizability, and hyperpolarizability, indicating improved sensitivity to electric fields. Furthermore, thermoelectric analysis showed lower Joule and Peltier heat generation in the thionated configuration, suggesting higher energy efficiency. These results highlight the effectiveness of thionation as a molecular design strategy and establish diimide-phenyl tetra-nitro as a promising candidate for next-generation single-molecule electronic devices.