Computational investigations of S3 structures related to a recent X-ray free electron laser study

Recent free-electron laser (X-FEL) studies have suggested S₃ states with many features as expected based on previous model calculations and spectroscopy. However, in one of them there is one dramatic surprise. An hydroxide (at the O6 position) on Mn1 was expected, but this group is missing in that X-FEL structure. It has previously been concluded that the hydroxide, which fills the sixth position of the octahedral coordination of Mn1, is necessary to oxidize this manganese to form the S₃ state. In the present study, S₃ structures without the O6 hydroxide have been investigated. Finally, also some S₂ structures were studied.