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

A series of twelve selenourea compounds with fluorinated fragments were synthesized and characterized. The influence of fluorine atoms in the chemical shift of the Se-77 NMR was studied. The more fluorine atoms in the structure produced a downfield shift of the Se-77 signal, indicating a higher pi-acidity character in the N-heterocycle. The relative position of the fluorine atom also affects the chemical shift of the Se-77. 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: SeMIDLINE HORIZONTAL ELLIPSISH, FMIDLINE HORIZONTAL ELLIPSISF and FMIDLINE HORIZONTAL ELLIPSISH. The latter was corroborated by Hirshfeld surface analysis and 2D dimensional fingerprint plots of each crystal structure.