Preservation of endometallofullerene La@C82 in polycarbonate: EPR, ENDOR, and NMR studies

On embedding in poly(bisphenol A carbonate) film, La@C82 has featured the exclusive stability against oxygen for more than 1 year's storage of the polymer films on air. The EPR spectral parameters of La@C82 have occurred to be sensitive to the segmental mobility and the phase transition of the polymer from the glassy to the high-elasticity state. Furthermore, the intense matrix 1H-electron nuclear double resonance (ENDOR) signal discovered in this system testifies the partial transfer of the electron spin density outside the fullerene cage onto the polymer protons. The 139La NMR spectrum of the same suggests that La@C82 forms nanoparticles, in which the metal atoms strongly interact with the delocalized electrons. The “spin-leakage” of the fullerene shell, along with the tendency of endohedral fullerenes (EMF) to form nanoparticles, is worth consideration in sight of their applications in material sciences.