An experimental and theoretical approach to the study of the properties of parabanic acid and related compounds: synthesis and crystal structure of diethylimidazolidine-2-selone-4,5-dione

The syntheses of the first examples of selenoparabanic acid derivatives (dialkylimidazolidine-2-selone-4,5-dione, 3e(R) R = Me, Et, Bu) are presented along with the X-ray crystal structure determination of 3e(Et). To gain an insight in the properties of parabanic acid derivatives on the basis of their electronic structures, we report the results of comparative hybrid-DFT calculations performed on parabanic, thioparabanic, and selenoparabanic acids (3a(H), 3b(H), and 3e(H)) and on their N,N' -dimethyl derivatives (3a(Me), 3b(Me), and 3e(Me)). Calculations show that the different nature of the frontier orbitals of 3a(R) compared to those of 3b(R) and 3e(R), might account for the different reactivities of these compounds. Moreover, the weak donor character of 3b(R) and 3e(R) towards molecular di-iodine, estimated by FT-Raman measurements is in agreement with the calculated NBO-charge distribution.