Theoretical Study Of The Metal Sulfide Fullerenes And C₅₈-C₆₂

The metal atoms or metal clusters could be inserted into bare cage,which is called endohedral metallofullerenes(EMFs).There are various metal atoms and metal clusters,and the number of fullerene cages increases rapidly with the growth of carbon atoms.Thus,the quantity of endohedral metallofullerenes is very huge.Endohedral metallofullerenes have attracted attention because of their unique physical and chemical properties.Although many endohedral metallofullerenes and their isomers have been isolated and purified at present,which makes it possible to study their structure and physicochemical properties,structural identification is still a difficult task in the study of metallofullerenes due to the low yield and immature experimental technology.In order to develop new synthetic methods for the preparation of high yield products,we must understand structural relationships and formation mechanism of these isomers.In addition to classical fullerenes,it has been found recently that non-classical fullerenes containing a heptagon can also be used as a parent cage for endohedral trimetallic nitride template fullerenes.Therefore,it is necessary to study the structure and properties of non-classical fullerenes.In this paper,systematical density functional theory calculations were performed on metal sulfide fullerenes Sc2S@C2n(n=35-42),and it is proved that there is a close structural interdependence amongst the favoured isomers of Sc2S@C2n with size from C70 to C84,which provides theoretical proof for the formation mechanism of fullerenes.In addition,the classical and non-classical structure of C58,C60 and C62 were also studied by theoretical research.1)An atlas of endohedral Sc2 S cluster fullerenesThe thermodynamic and kinetic stability of Sc2S@C2n(n=35-42)were calculated by density functional theory.The results demonstrate that metal sulfide fullerenes Sc2S@C2n have similar cage geometries from C70 to C84,which form a close-knit family of structures related by Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization transformations.Many of the lowest energy isomers of Sc2O@C2n share the same cages with Sc2S@C2n apart from the cages with n=74,78 and 84.Since both Sc2 O and Sc2 S tend to donate 4 electrons to a fullerene cage,they tend to select the same isomer as host cage and these results indicate that electron transfer interactions play a vital role.The stabilities predicted for favoured isomers by DFT calculations are in good agreement with available experimental observations,have implications for the formation of metallofullerenes,and will aid structural identification from within the combinatorially vast pool of conceivable isomers.2)From C58 to C62 and back: stability,structural similarity,and ring currentNon-classical isomers may play an important role in the formation of fullerenes and their exo-and endo-derivatives.Systematic density functional theory calculations of all classical isomers of C58,C60 and C62,and all non-classical isomers with at most one square or heptagonal face,was carried out.The results indicate that the favored isomers of C58,C60 and C62 have closely related structures and suggest plausible interconversion and growth pathways among low-energy isomers.Ring currents can be induced on faces of these polyhedral cages by radical external magnetic fields.Ring-current simulations demonstrate that both squares and pentagons support paratropic current under radial magnetic fields,whereas diatropic ring current is in hexagons and heptagons.Similarity of the favored structures can be further confirmed by calculated ring currents.