(Invited) Recent Developments Regarding Orientation Studies of Endohedral Nitrogen Fullerenes and Their Water-Solubilization

Abstract

Paramagnetic endohedral fullerenes hold promise for a number of applications including quantum information processing and quantum sensing. In the case of endohedral nitrogen fullerenes such as N@C60 and N@C70, the nitrogen atom is almost completely isolated from the fullerene cage. This results in very long electron spin phase coherence times. The chemistry of endohedral nitrogen fullerenes has developed to a degree where it can be used to create functionalized systems with high aspect ratios that are prone to high alignment. In this talk, I will present our recent results for several N@C60 and N@C70 derivatives that we have aligned in liquid crystals. Within the liquid crystal matrix, we have achieved an order parameter factor Ozz of 0.61. This is a significant improvement on the best result that has been previously reported for endohedral fullerene derivatives. More importantly, this allows us to manipulate the intrinsic zero-field splitting (ZFS) of the spin resonance signal. By in-situ rotating frozen endohedral fullerenes inside the magnetic field of the ESR spectrometer, we deliberately changed the orientation distribution of the molecules and tuned the splitting energy of ZFS. We achieved remarkable agreement between experimental values and simulation data. This work can be expanded to control of dipolar coupling for a two-qubit gate. Hence it is quite pertinent to research on potential applications of endohedral fullerenes. In my talk, I will also touch upon the water functionalization of N@C60. We have developed the first water-soluble derivative of N@C60 and we have shown that it has the potential to be used as a quantum sensor for other spin-active species.