Spin‐tautomery of endohedral Y@C60 complex

Abstract New conception of spin‐tautomery was developed based on the results of quantum chemical investigation of the endohedral Y@C 60 complex. The embedding energies of yttrium into the fullerene cavity, dipole moments, polarizabilities, and IR spectra in the doublet and quartet spin states were calculated by the density‐functional theory quantum chemical methods. The degeneracy degree of the state of the complex is retained upon doublet–quartet excitation, since a twofold increase in the number of electron spin projections is compensated by a twofold decrease in the number of equivalent potential energy minima. The non‐conservation of spin by an endohedral complex with a heavy atom makes it possible to interpret the interconversion of doublet and quartet states as a non‐degenerate spin‐tautomery.