Schleyer hyperconjugative aromaticity as an efficient strategy to induce more delocalization in penguinone and thiopenguinone derivatives: a DFT investigation

In this study, the impact of Schleyer hyperconjugative aromaticity on penguinone and thiopenguinone derivatives was systematically investigated using DFT at the B3LYP/6-311 + G(d, p) level. Structural, electronic, and magnetic aromaticity indices were computed to evaluate the delocalization character of the designed systems. The results reveal that bulky electron-donating substituents such as –GeMe 3 and –SiMe 3 significantly enhance delocalization through electron injection and formation of a pseudo-6π electron system. In contrast, the electron-withdrawing –F substituent reduces electron delocalization and aromatic stabilization. Sulfur-containing derivatives exhibit relatively more delocalization in several cases, attributed to the larger atomic size and lower electronegativity of sulfur compared to oxygen. A strong correlation was observed among most aromaticity indices. Overall, Schleyer hyperconjugation emerges as an effective strategy for inducing delocalization in inherently nonaromatic frameworks.