Which Do Endohedral Ti₂C₈₀ Metallofullerenes Prefer Energetically:  Ti₂@C₈₀ or Ti₂C₂@C₇₈? A Theoretical Study

Abstract

Four possible isomers of the Ti2C80 metallofullerene are discussed in detail at the B3LYP DFT level of theory: two isomers in Ti2@C80 formula with two Ti atoms encapsulated inside a C80 cage and the other two in Ti2C2@C78 formula with a Ti2C2 cluster involved inside a C78 cage. In the encaged Ti2C2 cluster, there are end-on and side-on C2 bridging modes into the two Ti atoms. The optimized end-on cluster has a linear Ti-C-C-Ti array, whereas the side-on cluster has a butterfly-like structure where the two Ti atoms and the C2 unit do not lie in a plane. DFT calculations show that the Ti2C2@C78 molecule with the end-on Ti2C2 cluster is energetically most favorable in the four isomers. Stabilities of the Ti2C80 molecules are essentially dominated by Ti binding sites inside fullerene cages. The Ti atoms bind over the hexagon rings in preference to a junction between hexagon and pentagon rings. In the Ti2C2@C78 molecules, orbital interactions between the Ti2C2 cluster and the outer cage play a significant role in determining the C2 bridging modes into the dititanium center and their relative stabilities.

Molecular geometries, electronic properties, and vibrational spectroscopic studies of endohedral metallofullerenes TM@C24 and TM@C24H12 (TM = Cr, Mo, and W)

“…In the meantime, some endohedral complexes doped with various small molecules or ions have also been obtained [34][35][36][37][38][39][40][41][42][43][44][45][46][47]. For example, Gan [36] have reported the structures and stabilities of dimetallofullerenes M 2 @C n (M = Sc and La, n = 72, 76, 78, 80, and 84) with local density functional (LDA) method, and demonstrated that the two metallic atoms always tend to separate as long as possible inside fullerene cage.…”

“…For example, Gan [36] have reported the structures and stabilities of dimetallofullerenes M 2 @C n (M = Sc and La, n = 72, 76, 78, 80, and 84) with local density functional (LDA) method, and demonstrated that the two metallic atoms always tend to separate as long as possible inside fullerene cage. Yumura et al [39] have discussed the possible isomers of the Ti 2 @C 80 metallofullerene using the hybrid DFT-B3LYP functional, and found that Ti bindings over the hexagon ring are energetically preferable relative to those over a junction between hexagon and pentagon rings. Rehaman et al [44] have studied the pocket and antipocket conformations of CH 4 @C 84 using density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2), and found that the antipocket conformation have an alternative minimum.…”

Metal-Cage Bonding, Molecular Structures and Vibrational Spectra of Endohedral Fullerenes: Bridging Experiment and Theory

“…), [49][50][51][52][53] and there are theoretical and experimental indications that Ti 2 @C 80 is actually a Ti 2 C 2 @C 78 . [54][55][56] Recently, Sc 2 C 2 @C 68 with non-IPR carbon cage was isolated. 57 The studies of endohedral fullerenes have already reached the state when the survey of the whole field in one medium-size article is hardly possible.…”

Large Gadolinium Nitride Cluster Encapsulated inside a Non‐IPR Carbon Cage: A Theoretical Characterization on Gd3N@C78

“…Many other C 78 -based EMFs have been extracted successfully and most of them were determined to possess the IPR carbon cage D 3h (24109)ÀC 78 , such as La 2 @C 78 , [28,29] Ce 2 @C 78 , [30] Ti 2 C 2 @C 78 , [31][32][33][34] and Sc 3 N@C 78 . [35,36] In contrast, the major isomers of Dy 3 N@C 78 and Tm 3 N@C 78 were proposed to bear the same non-IPR carbon cage with Gd 3 N@C 78 .…”