Recently, planar and neutral tricoordinated oxygen embedded in graphene has been imaged experimentally (Nat. Commun., 2019, 10, 4570-4577). In this work, this unusual chemical species is studied utilizing a variety of state-of-the-art methods and combining periodic calculations with a fragmental approach. Several factors influencing the stability of trivalent oxygen are identified. A σ-donation and a π-backdonation mechanism between graphite and oxygen is established. π-Local aromaticity, with a delocalized 4c-2e bond involving the oxygen atom and the three nearest carbon atoms aids in the stabilization of this system. In addition, the framework in which the oxygen is embedded is crucial too to the stabilization, helping to delocalize the "extra" electron pair in the virtual orbitals. Based on the understanding gathered in this work, a set of organic molecules containing planar and neutral trivalent oxygen is theoretically proposed for the first time.
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