Electronic properties and supramolecular study of selenoureas with fluorinated-NHC ligands derived from imidazo[1,5-a]pyridines

Abstract

A series of twelve selenourea compounds with fluorinated fragments were synthesized and characterized. The influence of fluorine atoms in the chemical shift of the 77Se NMR was studied. The more fluorine atoms in the structure produced a downfield shift of the 77Se signal, indicating a higher π-acidity character in the N-heterocycle. The relative position of the fluorine atom also affects the chemical shift of the 77Se. It can be seen that a fluorine atom at 3-position, following by 4- and 2-position, respectively, produced a higher downfield shift. Interestingly, the opposite effect was observed for the -CF3 group. The crystal structure of six selenourea compounds revelead that the predominant interactions were three: Se⋯H, F⋯F and F⋯H. The latter was corroborated by Hirshfeld surface analysis and 2D dimensional fingerprint plots of each crystal structure.