Interaction of free-base and 3d metal(II) phthalocyanines with open-shell endohedral fullerenes species N@C60 and P@C60

Abstract

We studied theoretically the interactions of phthalocyanines (Pcs) of general formula MPc (M = 2H, Mn, Fe, Co, Ni, Cu, Zn) with endohedral fullerenes (EFs) N@C60 and P@C60, at the PBE-D/DNP theoretical level. All MPcs can form stable noncovalent complexes with both N@C60 and P@C60. The binding energies vary between −17.7 and −31.1 kcal/mol. Complexation pattern depends on the central atom of MPc, but not on the endohedral species (N or P): for H2Pc, two central H atoms approach the carbon atoms of C60 of adjacent 5:6:6 junctions; for MnPc, manganese atom coordinates to two carbon atoms of 6,6 C-C bond; for other MPcs, the central metal coordinates to 5:6:6 junction of fullerene. In MPc+N@C60 HOMO is localized exclusively on phthalocyanine, with LUMO found mostly on fullerene. In MPc+P@C60 complexes, HOMO has essentially the same localization and shape, but LUMO distribution is variable. After complexation with MPcs, no tangible changes are observed in the N and P spin state. MnPc, CoPc and CuPc having open-shell metal atoms behave differently: while the complexation has almost no effect on Cu spin, and causes only a moderate decrease in Co spin, Mn atom transfers roughly two-thirds of its unpaired electrons to fullerene.