Structural behavior of rhenium complexes in fluoride sensing: a spectroscopic and computational study

In this study, three rhenium(I) complexes functionalized with amide ( 1a ), urea ( 1b ), and thiourea ( 1c ) moieties appended to bipyridine ligand were used as model systems to investigate the structural and spectroscopic behavior in the presence of fluoride ion. These rhenium(I) complexes were capable of detecting fluoride ion, although the structural changes of rhenium(I) complex in the presence of fluoride ion is unknown. Raman and infrared spectroscopic techniques were employed to examine the vibrational features of rhenium complexes in the presence of fluoride ion. UV–Visible absorption spectroscopic studies showed that after the addition of fluoride ion, the ligands became more σ-donating, and the lowest energy transition is changed from metal-to-ligand charge transfer (MLCT) to intraligand charge transfer transition (ILCT). Furthermore, these investigations are supported by density functional theory/time dependent–density functional theory (DFT/TDDFT) computational studies.