Nature of the interaction of paramagnetic atoms (A=~4N,~4P,~3O,~3S) with #pi# systems and C_(60): A theoretical investigation of A…C_6H_6 and endohedral fullerenes A@C_(60)

摘要

The nature of the interaction of paramagnetic atoms A (=~4N,~4P,~3O,~3S) with #pi# systems and C_(60) in the A…C_6H_6 complexes and endohedral fullerenes (A@C_(60)) has been investigated employing second-order Moller-Plesset perturbation level of theory and density functional theory calculations. The coupled cluster theory with single and double excitations, and with perturbed triplet excitations have also been carried out for the A…C_6H_6 complexes. The calculated geometries indicate that the paramagnetic N and P atoms lie on the C_6 axis of benzene in the A…C_6H_6 complex and at the center for the C_(60) cage in A@C_(60). On the other hand, the O and S atoms are slightly shifted towards the C-C bond of benzene in the A…C_6H_6 complex. A comparison of the calculated binding energies (BEs) of these paramagnetic complexes and the corresponding rare gas complexes like He…C_6H_6 and He@C_(60) indicate that the BEs of the former are much larger than those of the latter. For both the rare gas and paramagnetic atom complexes dispersive intractions dominate the BEs. The energy barriers of the penetration of the O atom through a [6,6] bond are lower than the penetration of the helium atom and higher than the penetration of a N atom.