Probing the C₆₀ triplet state coupling to nuclear spins inside and out.

The photoexcitation of functionalized fullerenes to their paramagnetic triplet electronic state can be studied by pulsed electron paramagnetic resonance (EPR) spectroscopy, whereas the interactions of this state with the surrounding nuclear spins can be observed by a related technique: electron nuclear double resonance (ENDOR). In this study, we present EPR and ENDOR studies on a functionalized exohedral fullerene system, dimethyl[9-hydro (C60-Ih)[5,6]fulleren-1(9H)-yl]phosphonate (DMHFP), where the triplet electron spin has been used to hyperpolarize, couple and measure two nuclear spins. We go on to discuss the extension of these methods to study a new class of endohedral fullerenes filled with small molecules, such as H₂@C₆₀, and we relate the results to density functional calculations.