Publication

Abstract : Density functional theoretical calculations were performed to study the stability and magnetic properties of nitrogen-encapsulated C60, C59N, and their respective dimers at B3LYP/6-311G* and B3LYP-GD2/6-311G* levels of theory. For the most stable spin state of each of the above complexes, spin density transfer and spin–spin coupling between different components are investigated. The nature of bonding between the guest and the host is analyzed based on the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap and the respective molecular orbital diagrams. The analysis of spin density showed that the encapsulated nitrogen retained its atomic state in N@C60 and N@C59N. Depending on the multiplicity of N@C59N, the unpaired electrons of the encapsulated nitrogen are coupled with those of the cage anti-ferromagnetically or ferromagnetically. The present study also showed that the complex (N@C60)2 can exist in two isoenergetic spin states, namely, 7[(N@C60)2] and 1[(N@C60)2]. In the former, the encapsulated nitrogens are ferromagnetically coupled, whereas they are coupled anti-ferromagnetically in the latter. A similar coupling between the guest species occurs in the nitrogen analogues 7[(N@C59N)2] and 1[(N@C59N)2]. The stabilization energy of the endohedral nitrogen complexes indicated that the interaction between the guest and the host cage is purely noncovalent.