Anharmonic Vibrational Frequencies and Spectroscopic Constants for the Six Conformers of 1,2-Diiminoethane: A Promising Prebiotic Molecule for Astronomical Detection

The search for the molecular origins of life likely must go through polyimines, and this quantum chemical work shows that the anti-(E,Z)-1,2-diiminoethane molecule would be the next natural step as a detection target. This conformer exhibits a 2.78 D dipole moment and is the second-lowest-energy conformer after the nonpolar anti-(E,E) form. Additionally, the previously assigned N–H antisymmetric stretch of the lowest-energy anti-(E,E) conformer should likely be decreased in frequency to closer to 2930 cm^–1. The full set of anharmonic, fundamental vibrational frequencies and spectroscopic constants of all six conformers are produced in this work and will aid in any possible, future characterization of 1,2-diiminoethane and its possible role in the buildup of prebiotic molecules where multiple C = N bonds are required.