A quantum chemical investigation of electro-optical properties and spectroscopic features of propargylimine

Propargylimine HC≡CH–CH=NH, detected toward the Galactic Center molecular cloud G+0.693–0.027, is a potential a nitrogen-bearing 3C-atom species in prebiotic chemistry. In this study, we present a comprehensive computational investigation of its thermodynamics, reaction mechanism, electro-optical properties, global reactivity descriptors, and vibrational spectroscopic signatures. The formation of Z and E conformers of propargylimine was explored through radical–radical association pathway in the gas phase using density functional theory (DFT) (M06-2X/aug-cc-pVTZ), and benchmarked with CCSD(T)/aug-cc-pVTZ single-point calculations. Thermodynamic parameters, electro-optical properties, global reactivity descriptors, and molecular electrostatic potential surfaces were evaluated to assess its chemical stability and detectability. The simulated infrared spectrum provides characteristic vibrational markers, particularly the C=N stretch at 1691.9 cm −1 and N–H stretching bands (∼3430–3447 cm −1 ), which may facilitate astronomical identification. UV absorption features and the electronic absorption properties of propargylimine were investigated using time-dependent (TD)-DFT. This work offers a theoretical framework for understanding its formation and spectroscopic features, reinforcing its role as a chemically robust molecule in the nitrogen-bearing chemistry and molecular complexity in Galactic Center molecular clouds.