Probing the Interaction of NO with C 60 : Comparison between Endohedral and Exohedral Complexes.

Recent advances in synthetic methodologies have opened new strategies for synthesizing stable metal-free electron spin systems based on fullerenes. Introducing nitric oxide (NO) inside a fullerene cage is one of the methods to attain this goal. In the present study, dispersion corrected density functional theory (B3LYP-D3) has been used to evaluate the structure, stability, and electronic properties of NO encapsulated fullerene NO@C and compared those with its exohedral fullerene NO.C analog. The calculated stabilization energy for NO@C is appreciably higher than NO.C, and this difference is comprehended via the Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) topological analyses. The delocalization of electron density of NO and the C cage in NO@C is discussed using electrostatic potential analysis. In addition, an attempt has been made to understand the different locations and orientations involving the interaction of two NO radicals and the fullerene C. It is shown that the encapsulation of the NO dimer inside the C cage is an energetically unfavorable process. On the other hand, stable structures are obtained upon the physisorption of other NO on the surface of NO@C and NO.C. The present work provides an in-depth understanding of the interaction of NO and C fullerene, its preferable position, and its orientation in both endohedral and exohedral complexes.