Spectroscopic discernibility of dopants and axial ligands in pyridinic FeN environments relevant to single-atom catalysts.

Single-atom catalysts (SACs) activate small molecules, e.g. the oxygen reduction reaction is catalysed by FeNC materials. Because the nature of active site(s) in this type of SAC is unclear, spectroscopic and computational insights are needed to clarify the atomistic composition and electronic structure. Using quantum chemistry, we show that key features of [Fe{phen2A2}L]n+ complexes (A = CH, N with n = 0, A = O with n = 0, 2; L = OH-, Cl-) can be differentiated spectroscopically.