The synthesis of endohedral metallofullerenes (EMFs) from a carbon soot sample of an arc discharge leads to a variety of EMFs that are obtained in different relative abundances. In the present work, we show that these abundances can be predicted from aromaticity calculations. In particular, we use the normalized Additive Local Aromaticity (ALAN) index. Our results show that the most abundant Sc3N-based and Y3N-based EMFs in fullerene soot are the most aromatic. This study reinforces the idea that aromaticity plays a key role in determining the stability of EMFs

We are grateful for financial support from the Spanish MINECO (CTQ2014-54306-P, CTQ2014-52525-P, CTQ2014-59212-P, and RyC contract to S.O.), the Catalan DIUE (2014SGR931, ICREA Academia 2014 Award to M.S. and XRQTC), and the FEDER fund (UNGI10-4E-801). M.G.-B. thanks the Spanish MECD for a PhD grant (AP2010- 2517) and the Ramón Areces Foundation for a postdoctoral fellowship. S.O. thanks the European Community for the CIG project (PCIG14-GA-2013-630978), and acknowledges the funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (ERC-2015-StG-679001)