In this study, the nonequilibrium green\\\\\\\\\\\\\\\'s function (NEGF) combination with density functional theory (DFT) was used to investigate the molecular switching properties in some β-diketones with different alkyl and methoxy groups in their beta positions. The compounds used in this research are: 1,7-dimercapto-2,2,6,6-tetramethyl-3 5-heptanedione (STMHDS), 1,7-dimercapto3,5-Heptanedione (SHPDS), 1,5-dimercaptopentane-2,4-dione (SAAS), and mercaptomethyl 4-mercapto-3-oxobutanoate (SMOBS). In these four compounds, in most cases, the current in keto form is lower than in the enol form. We thoroughly examined the STMHDS molecule, including different electrodes (Pt, Au, and Ag), the types of connection states (top, bridge, and hollow), the on-off ratios, the HOMO-LUMO gaps, the I-V, and the transmission spectra. For this molecule, the best connection is hollow, so the same type of connection is considered for all calculations. With changing the enol form to keto form, the conductivity changed from the on-state (low resistance) to the off-state (high resistance). The best electrodes with the highest current ratios in STMHDS, SHPDS, SAAS, and SMOBS are Au, Au, Pt, and Ag, respectively. Because the ratios in SHPDS, SAAS, and SMOBS molecules are much smaller than that in STMHDS molecule, the transmission spectra and the HOMO-LUMO gaps cannot explain which form is more conductive.

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