Syntheses, Structures and Antioxidant Activities of Fullerenols: Knowledge Learned at the Atomistic Level

Abstract

Fullerenol nanoparticles have intriguing potentials in biomedical applications. However, the structures, mechanisms of syntheses and mechanisms of antioxidant activities of fullerenols at the atomistic level, which substantialize their properties and applications, remain opened questions. Here, we review the syntheses, structures and antioxidant activities of fullerenols. Especially, we focus on the knowledge at the atomistic level. Experimentally, fullerenols can be synthesized using oxidation reactions in either acidic conditions or alkaline conditions. The latter reactions yield fullerenols with high hydroxyl numbers and better water solubility. For fullerenol structures, a precision structural model has been recently proposed for C-60 fullerenols, which explain the experimentally-observed radical anion properties and pH-dependent infrared spectroscopic properties. Calculations have suggested that the most thermodynamically stable structures of many fullerenols have hydroxyls located aggregately in islands on the fullerene cages, although the most stable configuration of C-60(OH)(24) has hydroxyls distributed on C-60 equator. Two different center dot OH-scavenging mechanisms are possible for fullerenols. Fullerenols with low degrees of hydroxylation prefer the center dot OH addition mechanism, whereas those with high degrees of hydroxylation prefer the hydrogen abstraction mechanism. The O (2) (a (TM) a') -scavenging mechanism is related to redox potentials, charges and H-bond nets of the fullerenols.