Structural interconnections and the role of heptagonal rings in endohedral trimetallic nitride template fullerenes

Phys. Chem. Chem. Phys.

et al. 2017

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Abstract:Structural identification is a difficult task in the study of metallofullerenes, but understanding of the mechanism of formation of these structures is a pre-requisite for new high-yield synthetic methods. Here, systematic density functional theory calculations demonstrate that metal sulfide fullerenes Sc 2 S@C n have similar cage geometries from C 70 to C 84 and form a close-knit family of structures related by Endo-Kroto insertion/extrusion of C 2 units and Stone-Wales isomerization transformations. The stabilities predicted for favored 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.

Section: Computational Detailsmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

An atlas of endohedral Sc₂S cluster fullerenes

Gan

Phys. Chem. Chem. Phys.

et al. 2017

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“…The focus of studies of classical fullerenes is now moving on to applications [6,7]. However, an increasing number of experimental and theoretical observations indicate that non-classical isomers play an important role in the formation of metallofullerenes and fullerene derivatives [8][9][10]. Even for the fullerenes themselves, formation mechanisms are still unclear in terms of the roles of heptagons and/or squares [11].…”

Section: Introductionmentioning

confidence: 99%

From C₅₈to C₆₂and back: Stability, structural similarity, and ring current

Gan

et al. 2016

J. Comput. Chem.

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An increasing number of observations show that non-classical isomers may play an important role in the formation of fullerenes and their exo-and endo-derivatives. A quantum-mechanical study of all classical isomers of C 58 , C 60 and C 62 , and all non-classical isomers with at most one square or heptagonal face, was carried out. Calculations at the B3LYP/6-31G* level show that the favoured isomers of C 58 , C 60 and C 62 have closely related structures and suggest plausible inter-conversion and growth pathways amongst low-energy isomers. Similarity of the favoured structures is reinforced by comparison of calculated ring currents induced on faces of these polyhedral cages by radial external magnetic fields, implying patterns of magnetic response similar to those of the stable, isolated-pentagon C 60 molecule.

“…Both experimental and theoretical studies demonstrate that the encaged metal atom will transfer some electrons to the parent cage . Our recent studies showed that the energy order of EMFs is roughly agreement with that of corresponding anions . For M 3 N@C n , the transferred electrons are six; for Sc 2 C 2 @C n and Sc 2 S@C n , the transferred electrons are four; for M@C n (M = Sc, Y, and Lanthanide atoms), the transferred electrons is three .…”

Section: Resultsmentioning

confidence: 67%

Structural connectivity and formation mechanism of monometallic cluster fullerenes YCN@C_n (n = 68–84)

Zhao

Cao

Int J of Quantum Chemistry

et al. 2018

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Excited by the recently experimental reports of monometallic cluster fullerenes, we examined the electronic and geometrical properties of monometallic cluster fullerenes YCN@C n with size from C 68 to C 84 by density functional theory and statistical thermodynamic calculations. The calculations demonstrate that the thermodynamically favored isomers of YCN@C n are in good agreement with available experimental results. Morphology analysis shows that the lowest-energy YCN@C n species are structurally connected by C 2 insertion/extrusion and Stone-Wales rotation, which can be promoted under high temperature; enthalpy-entropy interplay can change the relative abundances of low-energy isomers significantly at high temperature. All the results suggest that there is a structural evolution among these metallic cluster fullerenes in discharge condition, and thus, can rationalize their structural diversity in the soot and partly disclose their formation mechanism. The geometrical structures, electronic properties of these endohedral fullerene were discussed in detail. K E Y W O R D Sformation mechanism, monometallic cluster fullerenes, Stone-Wales rotation, structural evolution 1 | I N TR ODU C TI ON Fullerene molecules are hollow closed carbon cages containing 12 pentagons and n/2-10 hexagons. [1] The stability of bare fullerenes is usually determined by the isolated pentagon rule (IPR). [2] So far, all reported bare fullerenes have been known to satisfy the IPR. However, the parent cages of endohedral metallofullerenes (EMFs) can be non-IPR mainly due to the strong electron transfer interaction between encapsulated metallic atom (s)/cluster and the fullerene cages. [3] EMFs have attracted much attention owing to their unique geometrical structures, novel electronic properties, and potential applications. [4][5][6][7][8] It has long been thought that monometallofullerenes are only in the form of M@C 2n[9] and cluster fullerenes always encapsulate multiple metal atoms (two or more) inside. However, monometallic cluster fullerenes MCN@C n were successively reported since 2013. [10][11][12][13] The properties and applications of monometallic cluster fullerenes are different from both monometallic fullerenes and multimetallic cluster fullerenes due to the different geometrical and electronic structures of the encaged species. To our knowledge, the structural connectivity and formation mechanism of monometallic cluster fullerenes has not yet been clarified, although important progress has been made for empty fullerenes. [14] Therefore, it is of great interest to explore this new endohedral fullerene family. We, here, make a systematic computational study on monometallic cluster fullerenes YCN@C n (n 5 68-84). Interestingly, we find strong structural connectivity among the low-energy YCN@C n isomers in the form of C 2 insertion/extrusion and Stone-Wales transformations. [15] Our results provide clues to find new monometallic cluster fullerenes from the as-reported ones and partly disclose their formation mechanism.2 | C OM P UT ...