The photoluminescence of lanthanide ions inside fullerenes is usually very weak due to the quenching effect of the fullerene cage. In the case of Er@C82, the near-infrared emission from the Er3+ ion is completely quenched by the C82 fullerene cage. It remains challenging to turn on the photoluminescence of Er@C82 and other monometallofullerenes. In this work, we adopt a covalent modification strategy to alter the electronic structure of the fullerene cage for sensitizing the near-infrared emission of Er3+ ions in metallofullerenes Er@C2n (2n = 72, 76, and 82). After covalent modification with trifluoromethyl, phenyl, or dichlorophenyl groups, the erbium metallofullerenes exhibit photoluminescence at 1.5 μm, which is the characteristic emission of the Er3+ ion. Particularly, the otherwise nonfluorescent metallofullerene Er@C82 is transformed into fluorescent derivatives by using this strategy. The photoluminescence from the Er3+ ion is ascribed to energy transfer from the fullerene cage to the Er3+ ion. According to theoretical calculations, the sensitization of the Er3+ ion by the fullerene cage is associated with the large HOMO-LUMO gap and the closed-shell electronic structure of the metallofullerene derivatives. This work provides useful guidance for the design and synthesis of new fluorescent metallofullerenes.
The Cover Feature illustrates the dimerization of metallofullerene molecules through covalent bonding, which improves the nonlinear optical properties of metallofullerenes remarkably. More information can be found in the Article by Y. Jiang et al. on page 2995 in Issue 22, 2018 (DOI: 10.1002/cphc.201800797).
The design of molecular rotors that can rotate at ultrahigh speeds is important for the development of artificial molecular machines. Based on theoretical calculations, we demonstrate that two kinds of carbon nano-rings, i.e. [n]cycloparaphenylenes ([n]CPP) and cyclo[18]carbon (C18), can form an ultrafast ring-in-ring nano-rotor through π-π interaction. As a high-symmetry and low-barrier rotator, the rotational frequency of C18 in [11]CPP is close to the THz regime. At low temperatures, the motion of the [11]CPP:C18 system is purely rotational. As temperature increases, precession movements start to be observed and the motion resembles the behaviour of a gyroscope. The [11]CPP:C18 rotor can serve as a building block for bottom-up construction of more complex molecular machines.
Quality marker (Q-marker) serves as an important driver for the standardization of quality control in traditional Chinese medicine (TCM) formulas. However, it is still challenging to discover comprehensive and representative Q-markers. This study aimed to identify Q-markers of Hugan tablet (HGT), a famous TCM formula with ideal clinical effects in liver diseases. Here, we proposed a funnel-type stepwise filtering strategy that integrated secondary metabolites characterization, characteristic chromatogram, quantitative analysis, literature mining, biotransformation rules and network analysis. Firstly, the strategy of "secondary metabolites-botanical drugs-TCM formula" was applied to comprehensively identify the secondary metabolites of HGT. Then, the secondary metabolites with specificity and measurability in each botanical drug were identified by HPLC characteristic chromatogram, biosynthesis pathway and quantitative analysis. Based on literature mining, the effectiveness of botanical metabolites that met the above conditions was evaluated. Furthermore, the metabolism of the above metabolites in vivo was studied to reveal their biotransformation forms, which were used for network analysis. At last, according to biotransformation rules of the prototype drugs in vivo, the secondary metabolites were traced and preliminarily chosen as Q-markers. As a result, 128 plant secondary metabolites were identified in HGT, and 11 specific plant secondary metabolites were screened out. Then, the content of specific plant secondary metabolites in 15 batches of HGT was determined, which confirmed their measurability. And the results of literature mining showed that eight secondary metabolites had therapeutic effects in treating liver disease at the in vivo level, and three secondary metabolites inhibited liver disease-related indicators at the in vitro level. After that, 26 compounds absorbed into the blood (11 specific plant metabolites and their 15 metabolites in vivo) were detected in rats. Moreover, 14 compounds, including prototype components and their metabolites, were selected as Q-marker candidates by the "TCM formula-botanical drugs-compounds-targets-pathways" network. Finally, 9 plant secondary metabolites were defined as comprehensive and representative Q-markers. Our study not only provides a scientific basis for the improvement and secondary development of the quality standard of HGT, but also proposes a reference method for discovering and identifying Q-markers of TCM preparations.
Single-walled carbon nanotubes (SWCNTs) have evoked great interest for various luminescent applications, but the large emission heterogeneity resulting from the structural complexity of the samples seriously restricts their further development. Herein we theoretically explore the electronic structures and optical properties of phenine nanotubes (pNTs), which are typical luminescent SWCNT derivatives with determined molecular structures that have been synthesized recently (Z. Sun, K. Ikemoto, T. M. Fukunaga, T. Koretsune, R. Arita, S. Sato and H. Isobe, Science, 2019, 363, 151-155; K. Ikemoto, S. Yang, H. Naito, M. Kotani, S. Sato and H. Isobe, Nat. Commun., 2020, 11, 1807). Interestingly, pNTs are found to feature different semiconducting properties to SWCNTs, as indicated by a spatial separation trend in the HOMO and LUMO resulting from periodic structural vacancies. The HOMO-LUMO and optical gaps of pNTs depend inversely on their lengths and diameters, but diameter variation should be an ineffective method for property tuning due to its negligible influence. By contrast, chemical modifications via N doping or hydrogenation highly affect the HOMO-LUMO gaps and their distributions and greatly broaden the light absorption/emission range, and importantly, low-dose hydrogenation is predicted to be a feasible strategy to enhance luminescence. This work, by studying the fundamental photophysical properties of pNTs and making comparisons to SWCNTs, shows the promise of structural vacancy engineering and surface functionalization in acquiring multifunctional tube-like materials.
In this work, polyimide-based novel polymer dielectric materials, containing a cross-linkable olefin group and a long alkyl chain with biphenyl, were designed and synthesized by a mild chemical synthesis method to avoid thermal imidization so that they can be widely utilized.
Abstract Modulation of the reactivity of metallofullerenes is critical for production of metallofullerene derivatives with desired properties and functionalities. In this study, we investigate the effects of reduction and oxidation on the reactivity and regioselectivity in Diels–Alder reaction of metallofullerene La@C 82 by means of density functional theory calculations. Because of the enhanced electron‐deficiency characteristic upon oxidation, the oxidized metallofullerene exhibits higher thermodynamic and kinetic reactivity as compared with neutral La@C 82 . The regioselectivity in the reaction of La@C 82 with cylcopentadiene is remarkably changed after oxidation of the metallofullerene, which is explained in terms of the changes in the geometrical structure and the electronic structure of the metallofullerene. Quantitative analysis based on the activation‐strain model demonstrates that the low activation energy barrier for the reaction of the cation La@C 82 + with cyclopentadiene originates from small strain energy and large interaction energy between the reactants. Energy decomposition analysis on the transition states of the reactions reveals that the exchange‐repulsion interaction energy is one of the critical factors that determine the kinetic reactivity of the metallofullerene. This study not only provides new theoretical insights on how to modulate the reactivity of metallofullerenes, but also offers guideline for future experimental synthesis of new metallofullerene derivatives.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
