M@C78 (M = U, Th): Inherent Topological Connectivity Existed in Thermodynamically Stable Isomers and the Possibility of an Endohedral Fullerene Containing One Heptagon Ring.

The density functional theory combined with statistical thermodynamic analyses of M@C78 (M = U and Th) demonstrated that four isomers, M@D3h(24109)-C78, M@C2v(24107)-C78, M@C1(22595)-C78, and M@C1(23349)-C78, and a nonclassical isomer, M@C1(id7)-C78, containing one heptagon ring possess outstanding thermodynamic stabilities in the two M@C78 series. Especially, the M@C1(id7)-C78 isomer is the first nonclassical C78 fullerene that can exist stably. Importantly, these five fullerene cages are found to be related in the form of Stone-Wales (SW) transformations. Geometric analyses disclosed that, unlike lanthanide metals, actinide metals are more likely to bond with sumanene-type hexagonal rings when they are encapsulated in IPR C78 cages. Frontier molecular orbital analysis showed that both U and Th atoms donate four electrons to the C78 carbon cages.

Efficiency comparison with fovea-sparing internal limiting membrane peeling and complete internal limiting membrane peeling for treating myopic traction maculopathy.

PURPOSE: To explore whether the efficacy of fovea-sparing internal limiting membrane peeling (FS-ILMP) is better than that of complete internal limiting membrane peeling (ILMP). METHODS: This retrospective clinical study included 34 cases (34 eyes) with myopic traction maculopathy collected from June 2017 to February 2019. Twenty-three-gauge (23-G) pars plana vitrectomy (23G PPV) was performed on all patients. In the FS-ILMP group, 18 eyes retained the internal limiting membrane (ILM) of about 1 to 1.5 papillary diameter centered on fovea centralis, while in the standard ILMP group, the ILM was completely removed from 16 eyes. The best corrected visual acuity (BCVA), central foveal thickness (CFT), and other indexes were collected before and 6 months after surgery. RESULTS: There was no significant difference in baseline clinical characteristics between the two groups. CFT and BCVA were significantly improved in both FS-ILMP and standard ILMP group, but the postoperative BCVA of the FS-ILMP group was significantly better than that of the standard ILMP group (P < 0.001). Two cases of subretinal effusion in macula were recorded in the FS-ILMP group, and three eyes in the standard ILMP group developed macular holes after surgery. Although both treatments relieved the mechanical traction of macular fovea, the patients in the FS-ILMP group showed better clinical outcomes in various aspects. CONCLUSION: These results improved our understanding of the clinical application of vitrectomy combined with preservation of ILM upon the fovea centralis, which might lay a foundation for in-depth study on the treatment of myopic traction maculopathy.

Theoretical Investigations of Lu2C84: Unexpected Impact of Metal Electronic Configuration toward the Metal-Metal σ-Bond in Fullerene.

Recent experimental works recovered multiformity of lutetium-involved dimetallofullerenes. On the basis of density functional theory (DFT) combined with statistical thermodynamic analyses, the relative stabilities of Lu2C84 dimetallofullerene were clarified. Besides the experimentally acknowledged Lu2@D2d(51591)-C84 and Lu2@C2v(51575)-C84, another four isomers metallofullerenes, Lu2@C1(51580)-C84, Lu2C2@Cs(39715)-C82, Lu2C2@C3v(39717)-C82, and Lu2C2@C2v(39718)-C82, are first proposed as thermodynamically stable structures. Interestingly, the geometric relationships among the pristine cages of stable Lu2C84 isomers through Stone-Wales transformation or C2 lose/insertion reveal important clues of the fullerene formation mechanism. The ionic interaction in the stable Lu2C84 isomers is revealed, and their valence states are Lu24+@C844- or (Lu2C2)4+@C824-. In the Lu2@C84 isomers, the results of frontier molecular orbital and natural bond orbital analyses suggest that a Lu-Lu single bond is formed, which is mainly composed of the 6s and 6p orbitals of the Lu atoms. Further analyses of the M2@C84 (M = Sc, Y, La, and Yb) structures disclose the importance of the electron configuration of metal element toward the formation of a single metal-metal bond in C84. Moreover, the covalent interaction between the Lu2 moiety and the C84 cages is disclosed, which is a supplement to the ionic model.

Encapsulation of Monometal Uranium into Fullerenes C2n (2n = 70-74): Important Ionic U4+C2n4- Characters and Covalent U-Cage Bonding Interactions.

By using density functional theory calculations combined with statistical thermodynamic analyses, the stabilization performance of a series of fullerene cages C2n (2n = 70-74) via encapsulating monometal uranium was systematically and thoroughly investigated. Results indicate that fullerene cages D5h(8149)-C70 and D3h(14246)-C74 obeying the isolated pentagon rule and C2(10612)-C72 featured with one pentalene moiety were the most promising candidates to encage uranium. Subsequent Mulliken spin density distribution and frontier molecular orbital analyses suggest that four formal electron transfer occurs from monometal U to above the carbon cages. There also exists a high degree of covalent character between the atom U and fullerenes C2n based on Mayer bond order and quantum theory of atoms in molecule (QTAIM) analyses, indicative of the cooperative stabilization by both ionic and covalent bonding interactions. In addition, investigations on the above-mentioned U@C2n isomers and other favorable candidates (U@Cs(8094)-C70, U@C1(10610)-C72, U@C1(13393)-C74, and U@C1(14049)-C74) reveal that these isomers could be closely linked via simple C2 addition and Stone-Wales transformation. These results will provide a systematic understanding on U-based endohedral metallofullerenes (EMFs) and also might be helpful for further exploration of EMF growth mechanisms.