Beyond Cation Effects: “Unveiling the Succinimide Anion's Key Role in CO 2 Fixation to Quinazoline‐2,4(1H,3H)‐dione”

ABSTRACT A gas‐phase quantum chemical computation was performed at the M06‐2X/6‐311++G(d,p) level to elucidate the electronic structure and non‐bonded interactions between nCO 2 and the succinimide anion ([Suc]). The present study focuses on structural and electronic interaction, revealing that the [Suc] anion can accommodate up to 8CO 2 molecules through diverse non‐covalent interactions. The Molecular Electrostatic Potential map (MESP) analysis revealed a decline in nucleophilicity as CO 2 absorption increased. The computed Fourier transform infrared spectroscopy (FTIR) showed a strong correlation with experimental data, validating the predicted vibrational features. While NCI‐RDG and QTAIM analyses showed the presence of stabilizing noncovalent contacts and bond critical points, confirming reversible CO 2 binding. Furthermore, the proposed reaction mechanism for CO 2 fixation into quinazoline‐2,4(1H,3H)‐diones established that the [HTMG][Suc] ionic liquid provides a highly favorable pathway. The [Suc] anion plays a key role in stabilizing intermediates and reducing the activation barrier to 4.19 kcal/mol, facilitating an efficient and thermodynamically favorable process. These findings deliver the first anion‐resolved mechanistic picture of [Suc]‐driven CO 2 activation and offer a strategic framework for designing advanced catalytic ionic liquid systems for efficient and sustainable CO 2 utilization.