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1.
The Regioselectivity of Bingel–Hirsch Cycloadditions on Isolated Pentagon Rule Endohedral Metallofullerenes 下载免费PDF全文
Dr. Marc Garcia‐Borràs Dr. Maira R. Cerón Dr. Sílvia Osuna Dr. Marta Izquierdo Dr. Josep M. Luis Prof. Dr. Luis Echegoyen Prof. Dr. Miquel Solà 《Angewandte Chemie (International ed. in English)》2016,55(7):2374-2377
In this work, the Bingel–Hirsch addition of diethylbromomalonate to all non‐equivalent bonds of Sc3N@D3h‐C78 was studied using density functional theory calculations. The regioselectivities observed computationally allowed the proposal of a set of rules, the predictive aromaticity criteria (PAC), to identify the most reactive bonds of a given endohedral metallofullerene based on a simple evaluation of the cage structure. The predictions based on the PAC are fully confirmed by both the computational and experimental exploration of the Bingel–Hirsch reaction of Sc3N@D5h‐C80, thus indicating that these rules are rather general and applicable to other isolated pentagon rule endohedral metallofullerenes. 相似文献
2.
Núria Alegret Dr. Antonio Rodríguez‐Fortea Prof. Josep M. Poblet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(16):5061-5069
An extensive theoretical study of the Bingel–Hirsch addition of bromomalonate on scandium nitride endohedral fullerenes has been carried out. The prototypical and highly symmetrical Sc3N@Ih‐C80, with a structure that satisfies the isolated pentagon rule (IPR), and the non‐IPR Sc3N@D3(6140)‐C68 fullerene show analogous reaction paths despite the distinct topology of the carbon networks and different rotation freedom of the internal nitride cluster. For the two metallofullerenes, our results predict that the reaction takes place under kinetic control yielding open‐cage fulleroids on [6,6] bonds, which is in good agreement with experimental data. The theoretical studies also show that predicting the reactivity of endohedral metallofullerenes is not straightforward and often an accurate analysis of the potential energy surface is required. 相似文献
3.
Julio R. Pinzón Tianming Zuo Dr. Luis Echegoyen Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(16):4864-4869
Bingel–Hirsch derivatives of the trimetallic nitride template endohedral metallofullerenes (TNT‐EMFs) Sc3N@Ih‐C80 and Lu3N@Ih‐C80 were prepared by reacting these compounds with 2‐bromodiethyl malonate, 2‐bromo‐1,3‐dipyrrolidin‐1‐ylpropane‐1,3‐dionate bromide, and 9‐bromo fluorene. The mono‐adducts were isolated and their 1H NMR spectra showed that the addition occurred with high regioselectivity at the [6,6] bonds of the Ih‐C80 fullerene cage. Electrochemical analysis showed that the reductive electrochemistry behavior of these derivatives is irreversible at a scan rate of 100 mV s?1, which is comparable to the behavior of the pristine fullerene species. The first reduction potential of each derivative is either cathodically or anodically shifted by a different value, depending on the attached addend. Bis‐adducts containing EtOOC‐C‐COOEt and HC‐COOEt addends were isolated by HPLC and in the case of Sc3N@Ih‐C80 the first reduction potential exhibits a larger shift towards negative potentials when compared to the mono‐adduct. This observation is important for designing acceptor materials for the construction of bulk heterojunction (BHJ) organic solar cells, since the polyfunctionalization not only increases the solubility of the fullerene species but also offers a promising approach for bringing the LUMO energy levels closer for the donor and the acceptor materials. 相似文献
4.
Yajing Hu Albert Solé-Daura Dr. Yang-Rong Yao Xuechen Liu Dr. Sijie Liu Ao Yu Dr. Ping Peng Prof. Josep M. Poblet Dr. Antonio Rodríguez-Fortea Prof. Luis Echegoyen Prof. Fang-Fang Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1748-1753
The chemistry of cationic forms of clusterfullerenes remain less explored than that of the corresponding neutral or anionic species. In the present work, M3N@Ih-C80 (M=Sc or Lu) cations were generated by both electrochemical and chemical oxidation methods. The as-obtained cations successfully underwent the typical Bingel–Hirsch reaction that fails with neutral Sc3N@Ih-C80. Two isomeric Sc3N@Ih-C80 cation derivatives, [5,6]-open and [6,6]-open adducts, were synthesized, and the former has never been prepared by means of a Bingel–Hirsch reaction with neutral clusterfullerenes. In the case of the Lu3N@Ih-C80 cation, however, only a [6,6]-open adduct was obtained. Density functional theory (DFT) calculations indicated that the oxidized M3N@Ih-C80 was much more reactive than the neutral compound upon addition of the diethyl bromomalonate anion. The Bingel–Hirsch reaction of M3N@Ih-C80 cations occurred by means of an unusual outer-sphere single-electron transfer (SET) process from the diethyl bromomalonate anion to the stable intermediate [M3N@C80(C2H5COO)2CBr].. Remarkably, the diethyl bromomalonate anion was found to act as both a nucleophile and an electron donor. 相似文献
5.
Reaction Mechanism and Regioselectivity of the Bingel–Hirsch Addition of Dimethyl Bromomalonate to La@C2v‐C82 下载免费PDF全文
Juan Pablo Martínez Dr. Marc Garcia‐Borràs Dr. Sílvia Osuna Dr. Jordi Poater Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5953-5962
We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel–Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C2v‐C82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C2v‐C82 by using dispersion‐corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C2v‐C82 is not particularly regioselective under Bingel–Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely. 相似文献
6.
Julio R. Pinzón Claudia M. Cardona Dr. Maria Ángeles Herranz Dr. Marta E. Plonska‐Brzezinska Dr. Amit Palkar Andreas J. Athans Dr. Nazario Martín Prof. Dr. Antonio Rodríguez‐Fortea Dr. Josep M. Poblet Prof. Dr. Giovanni Bottari Dr. Tomás Torres Prof. Dr. S. Shankara Gayathri Dr. Dirk M. Guldi Prof. Dr. Luis Echegoyen Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):864-877
The first pyrrolidine and cyclopropane derivatives of the trimetallic nitride templated (TNT) endohedral metallofullerenes Ih‐Sc3N@C80 and Ih‐Y3N@C80 connected to an electron‐donor unit (i.e., tetrathiafulvalene, phthalocyanine or ferrocene) were successfully prepared by 1,3‐dipolar cycloaddition reactions of azomethine ylides and Bingel–Hirsch‐type reactions. Electrochemical studies confirmed the formation of the [6,6] regioisomers for the Y3N@C80‐based dyads and the [5,6] regioisomers in the case of Sc3N@C80‐based dyads. Similar to other TNT endohedral metallofullerene systems previously synthesized, irreversible reductive behavior was observed for the [6,6]‐Y3N@C80‐based dyads, whereas the [5,6]‐Sc3N@C80‐based dyads exhibited reversible reductive electrochemistry. Density functional calculations were also carried out on these dyads confirming the importance of these structures as electron transfer model systems. Furthermore, photophysical investigations on a ferrocenyl–Sc3N@C80‐fulleropyrrolidine dyad demonstrated the existence of a photoinduced electron‐transfer process that yields a radical ion pair with a lifetime three times longer than that obtained for the analogous C60 dyad. 相似文献
7.
Essential Factors for Control of the Equilibrium in the Reversible Rearrangement of M3N@Ih‐C80 Fulleropyrrolidines: Exohedral Functional Groups versus Endohedral Metal Clusters 下载免费PDF全文
Safwan Aroua Marc Garcia‐Borràs Dr. Sílvia Osuna Dr. Yoko Yamakoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):14032-14039
The effects of exohedral moieties and endohedral metal clusters on the isomerization of M3N@Ih‐C80 products from the Prato reaction through [1,5]‐sigmatropic rearrangement were systematically investigated by using three types of fulleropyrrolidine derivatives and four different endohedral metal clusters. As a result, all types of derivatives provided the same ratios of the isomers for a given trimetallic nitride template (TNT) as the thermodynamic products, thus indicating that the size of the endohedral metal clusters inside C80 was the single essential factor in determining the equilibrium between the [6,6]‐isomer (kinetic product) and the [5,6]‐isomer. In all the derivatives, the [6,6]‐ and [5,6]‐Prato adducts with larger metal clusters, such as Y3N and Gd3N, were equally stable, which is in good agreement with DFT calculations. The reaction rate of the rearrangement was dependent on both the substituent of exohedral functional groups and the endohedral metal‐cluster size. Further DFT calculations and 13C NMR spectroscopic studies were employed to rationalize the equilibrium in the rearrangement between the [6,6]‐ and [5,6]‐fulleropyrrolidines. 相似文献
8.
Blending Non‐Group‐3 Transition Metal and Rare‐Earth Metal into a C80 Fullerene Cage with D5h Symmetry 下载免费PDF全文
Dr. Tao Wei Fei Jin Runnan Guan Prof. Dr. Jing Huang Dr. Muqing Chen Prof. Dr. Qunxiang Li Prof. Dr. Shangfeng Yang 《Angewandte Chemie (International ed. in English)》2018,57(32):10273-10277
Rare‐earth metals have been mostly entrapped into fullerene cages to form endohedral clusterfullerenes, whereas non‐Group‐3 transition metals that can form clusterfullerenes are limited to titanium (Ti) and vanadium (V), and both are exclusively entrapped within an Ih‐C80 cage. Non‐Group‐3 transition‐metal‐containing endohedral fullerenes based on a C80 cage with D5h symmetry, VxSc3?xN@D5h‐C80 (x=1, 2), have now been synthesized, which exhibit two variable cluster compositions. The molecular structure of VSc2N@D5h‐C80 was unambiguously determined by X‐ray crystallography. According to a comparative study with the reported Ti‐ and V‐containing clusterfullerenes based on a Ih‐C80 cage and the analogous D5h‐C80‐based metal nitride clusterfullerenes containing rare‐earth metals only, the decisive role of the non‐Group‐3 transition metal on the formation of the corresponding D5h‐C80‐based clusterfullerenes is unraveled. 相似文献
9.
Dr. Sílvia Osuna Dr. Ramón Valencia Dr. Antonio Rodríguez‐Fortea Prof. Marcel Swart Prof. Miquel Solà Prof. Josep M. Poblet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(29):8944-8956
In this work a detailed investigation of the exohedral reactivity of the most important and abundant endohedral metallofullerene (EMF) is provided, that is, Sc3N@Ih‐C80 and its D5h counterpart Sc3N@D5h‐C80, and the (bio)chemically relevant lutetium‐ and gadolinium‐based M3N@Ih/D5h‐C80 EMFs (M=Sc, Lu, Gd). In particular, we analyze the thermodynamics and kinetics of the Diels–Alder cycloaddition of s‐cis‐1,3‐butadiene on all the different bonds of the Ih‐C80 and D5h‐C80 cages and their endohedral derivatives. First, we discuss the thermodynamic and kinetic aspects of the cycloaddition reaction on the hollow fullerenes and the two isomers of Sc3N@C80. Afterwards, the effect of the nature of the metal nitride is analyzed in detail. In general, our BP86/TZP//BP86/DZP calculations indicate that [5,6] bonds are more reactive than [6,6] bonds for the two isomers. The [5,6] bond D 5h ‐b , which is the most similar to the unique [5,6] bond type in the icosahedral cage, I h ‐a , is the most reactive bond in M3N@D5h‐C80 regardless of M. Sc3N@C80 and Lu3N@C80 give similar results; the regioselectivity is, however, significantly reduced for the larger and more electropositive M=Gd, as previously found in similar metallofullerenes. Calculations also show that the D5h isomer is more reactive from the kinetic point of view than the Ih one in all cases which is in good agreement with experiments. 相似文献
10.
Crystallographic Evidence for Direct Metal–Metal Bonding in a Stable Open‐Shell La2@Ih‐C80 Derivative 下载免费PDF全文
Lipiao Bao Dr. Muqing Chen Changwang Pan Takahisa Yamaguchi Prof. Tatsuhisa Kato Prof. Marilyn M. Olmstead Prof. Alan L. Balch Prof. Takeshi Akasaka Prof. Xing Lu 《Angewandte Chemie (International ed. in English)》2016,55(13):4242-4246
Endohedral metallofullerenes (EMFs) have novel structures and properties that are closely associated with the internal metallic species. Benzyl radical additions have been previously shown to form closed‐shell adducts by attaching an odd number of addends to open‐shell EMFs (such as Sc3C2@Ih‐C80) whereas an even number of groups are added to closed‐shell EMFs (for example Sc3N@Ih‐C80). Herein we report that benzyl radical addition to the closed‐shell La2@Ih‐C80 forms a stable, open‐shell monoadduct instead of the anticipated closed‐shell bisadduct. Single‐crystal X‐ray diffraction results show the formation of a stable radical species. In this species, the La?La distance is comparable to the theoretical value of a La?La covalent bond and is shorter than reported values for other La2@Ih‐C80 derivatives, providing unambiguous evidence for the formation of direct La?La bond. 相似文献
11.
New Trifluoromethylated Derivatives of Metal Nitride Clusterfullerenes: Sc3N@Ih‐C80(CF3)14 and Sc3N@D5h‐C80(CF3)16 下载免费PDF全文
Tao Wei Dr. Nadezhda B. Tamm Prof. Dr. Shangfeng Yang Prof. Dr. Sergey I. Troyanov 《化学:亚洲杂志》2014,9(9):2449-2452
Trifluoromethylated derivatives of Sc3N@Ih‐C80 and Sc3N@D5h‐C80 were synthesized by the reaction with CF3I at 440 °C. HPLC separation of the mixture of Sc3N@D5h‐C80(CF3)n derivatives resulted in isolation and X‐ray structure determination of Sc3N@D5h‐C80(CF3)16, which represents a precursor of the known Sc3N@D5h‐C80(CF3)18. Among the CF3 derivatives of Sc3N@Ih‐C80, two new isomers of Sc3N@Ih‐C80(CF3)14 ( Sc‐14‐VI and Sc‐14‐VII ) were isolated by HPLC, and their molecular structures were determined by X‐ray diffraction, thus enabling a comprehensive comparison of altogether seven isomers. Two types of addition patterns with different orientations of the Sc3N cluster relative to the Ih‐C80 fullerene cage were established. In particular, Sc‐14‐VII represents a direct precursor of the known Sc3N@Ih‐C80(CF3)16‐ II . All molecular structures exhibit an ordered position of a Sc3N cluster inside the fullerene C80 cage. 相似文献
12.
Maira R. Cerón Dr. Fang‐Fang Li Prof. Dr. Luis Echegoyen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7410-7415
Based on the different oxidation potentials of endohedral fullerenes Sc3N@C80 Ih and D5h and Sc3N@C78, an efficient and useful method that avoids HPLC has been developed for their separation. Selective chemical oxidation of the Sc3N@D5h‐C80 isomer and Sc3N@C78 by using an acetylferrocenium salt [Fe(COCH3C5H4)Cp]+ followed by column chromatographic separation and reduction with CH3SNa resulted in the isolation of pure Sc3N@Ih‐C80, Sc3N@C78, and a mixture of Sc3N@D5h‐C80 and Sc3N@C68. 相似文献
13.
Preparation,Structural Determination,and Characterization of Electronic Properties of Bis‐silylated and Bis‐germylated Lu3N@Ih‐C80 下载免费PDF全文
Prof. Dr. Masahiro Kako Kyosuke Miyabe Dr. Kumiko Sato Dr. Mitsuaki Suzuki Dr. Naomi Mizorogi Dr. Wei‐Wei Wang Prof. Dr. Michio Yamada Prof. Dr. Yutaka Maeda Prof. Dr. Marilyn M. Olmstead Prof. Dr. Alan L. Balch Prof. Dr. Shigeru Nagase Prof. Dr. Takeshi Akasaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16411-16420
Bis‐silylated and bis‐germylated derivatives of Lu3N@Ih‐C80 ( 3 , 4 , 5 ) were successfully synthesized by the photochemical addition of disiliranes 1 a , 1 b or digermirane 2 , and fully characterized by spectroscopic, electrochemical, and theoretical studies. Interestingly, digermirane 2 reacts more efficiently than disiliranes 1 a and 1 b because of its good electron‐donor properties and lower steric hindrance around the Ge?Ge bond. The 1,4‐adduct structures of 3 , 4 , 5 were unequivocally established by single‐crystal X‐ray crystallographic analyses. The electrochemical and theoretical studies reveal that the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 1,4‐adducts are remarkably smaller than those of Lu3N@Ih‐C80, because the electron‐donating groups effectively raise the HOMO levels. It is also observed that germyl groups are slightly more electron‐donating than the silyl groups on the basis of the redox properties and the HOMO–LUMO energies of 4 and 5 . Bis‐silylation and bis‐germylation are effective and versatile methods for tuning the electronic characteristics of endohedral metallofullerenes. 相似文献
14.
Masahiro Kako Yuki Arikawa Shinji Kanzawa Michio Yamada Yutaka Maeda Makoto Furukawa Takeshi Akasaka 《Helvetica chimica acta》2019,102(5)
The reactions of novel S‐heterocyclic carbenes (SHCs), which were prepared by the cycloaddition of disilenes and digermenes to CS2, with C60 and Sc3N@Ih‐C80 afforded the corresponding methano‐bridged fullerenes. The [6,6]‐closed and [6,6]‐open structures were characterized for the SHC adducts of C60 and Sc3N@Ih‐C80, respectively. These derivatives exhibited relatively low oxidation potentials, indicative of the electron‐donating effects of the SHC addends. The electronic properties of the SHC derivatives were clarified by the density functional theory calculations. 相似文献
15.
Dr. Dmitri V. Konarev Dr. Alexey A. Popov Dr. Leokadiya V. Zorina Dr. Salavat S. Khasanov Prof. Dr. Rimma N. Lyubovskaya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(65):14858-14869
A series of compounds with Sc3N@Ih-C80 in the neutral, monomeric, and dimeric anion states have been prepared in the crystalline form and their molecular structures and optical and magnetic properties have been studied. The neutral Sc3N@Ih-C80 ⋅ 3 C6H4Cl2 ( 1 ) and (Sc3N@Ih-C80)3(TPC)2 ⋅ 5 C6H4Cl2 ( 2 , TPC=triptycene) compounds both crystallized in a high-symmetry trigonal structure. The reduction of Sc3N@Ih-C80 to the radical anion resulted in dimerization to form diamagnetic singly bonded (Sc3N@Ih-C80−)2 dimers. In contrast to {[2.2.2]cryptand(Na+)}2(Sc3N@Ih-C80−)2 ⋅ 2.5 C6H4Cl2 ( 3 ) with strongly disordered components, we synthesized new dimeric phases {[2.2.2]cryptand- (K+)}2(Sc3N@Ih-C80−)2 ⋅ 2 C6H4Cl2 ( 4 ) and {[2.2.2]cryptand- (Cs+)}2(Sc3N@Ih-C80−)2 ⋅ 2 C6H4Cl2 ( 5 ) in which only one major dimer orientation was found. The thermal stability of the (Sc3N@Ih-C80−)2 dimers was studied by EPR analysis of 3 to show their dissociation in the 400–460 K range producing monomeric Sc3N@Ih-C80.− radical anions. This species shows an EPR signal with a hyperfine splitting of 5.8 mT. The energy of the intercage C−C bond was estimated to be 234±7 kJ mol−1, the highest value among negatively charged fullerene dimers. The EPR spectra of crystalline (Bu3MeP+)3(Sc3N@Ih-C80.−)3 ⋅ C6H4Cl2 ( 6 ) are presented for the first time. The salt shows an asymmetric EPR signal, which could be fitted by three lines. Two lines were attributed to Sc3N@Ih-C80.−. Hyperfine splitting is manifested above 180 K due to the hyperfine interaction of the electron spin with the three scandium atoms (a total of 22 lines with an average splitting of 5.32 mT are observed at 220 K). Furthermore, each of the 22 lines is additionally split into six lines with an average separation of 0.82 mT. The large splitting indicates intrinsic charge and spin density transfer from the fullerene cage to the Sc3N cluster. Both the monomeric and dimeric Sc3N@Ih-C80− anions show an intrinsic shift of the IR bands attributed to the Sc3N cluster and new bands corresponding to these species appear in the NIR range of their UV/Vis/NIR spectra, which allows these anions to be distinguished from neutral species. 相似文献
16.
《化学:亚洲杂志》2017,12(12):1391-1399
Photochemical carbosilylation of Sc3N@Ih ‐C80 with silirane 1 afforded two corresponding [5,6]‐adducts, 2 and 3 , and a [6,6]‐adduct, 4 . The structural and electronic properties of these products were characterized by means of spectroscopic, electrochemical, and theoretical methods. The structure of 2 was disclosed by means of single‐crystal X‐ray crystallographic analysis. Thermal isomerization of 3 to 2 was observed, whereas that of 2 to 3 proceeded less efficiently at 100 °C. Upon heating under the same conditions, adduct 4 underwent facile decomposition to afford Sc3N@Ih ‐C80, or isomerized into small amounts of 2 and 3 . The relative stabilities of 2 , 3 , and 4 were rationalized through the results of theoretical calculations. In contrast, adducts 2 , 3 , and 4 were stable under the photolytic conditions employed for carbosilylation. The photochemical functionalization of Sc3N@Ih ‐C80 represents a convenient synthetic method to obtain thermally labile fullerene‐based products. 相似文献
17.
Marc Garcia‐Borràs Dr. Sílvia Osuna Dr. Josep M. Luis Prof. Marcel Swart Prof. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14931-14940
The chemical functionalization of endohedral metallofullerenes (EMFs) has aroused considerable interest due to the possibility of synthesizing new species with potential applications in materials science and medicine. Experimental and theoretical studies on the reactivity of endohedral metallofullerenes are scarce. To improve our understanding of the endohedral metallofullerene reactivity, we have systematically studied with DFT methods the Diels–Alder cycloaddition between s‐cis‐1,3‐butadiene and practically all X@Ih‐C80 EMFs synthesized to date: X=Sc3N, Lu3N, Y3N, La2, Y3, Sc3C2, Sc4C2, Sc3CH, Sc3NC, Sc4O2 and Sc4O3. We have studied both the thermodynamic and kinetic regioselectivity, taking into account the free rotation of the metallic cluster inside the fullerene. This systematic study has been made possible through the use of the frozen cage model (FCM), a computationally cheap approach to accurately predicting the exohedral regioselectivity of cycloaddition reactions in EMFs. Our results show that the EMFs are less reactive than the hollow Ih‐C80 cage. Except for the Y3 cluster, the additions occur predominantly at the [5,6] bond. In many cases, however, a mixture of the two possible regioisomers is predicted. In general, [6,6] addition is favored in EMFs that have a larger charge transfer from the metal cluster to the cage or a voluminous metal cluster inside. The present guide represents the first complete and exhaustive investigation of the reactivity of Ih‐C80‐based EMFs. 相似文献
18.
Isolation of CeLu2N@Ih‐C80 through a Non‐Chromatographic,Two‐Step Chemical Process and Crystallographic Characterization of the Pyramidalized CeLu2N within the Icosahedral Cage 下载免费PDF全文
Prof. Dr. Steven Stevenson Hannah R. Thompson Kristine D. Arvola Kamran B. Ghiassi Prof. Dr. Marilyn M. Olmstead Prof. Dr. Alan L. Balch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10362-10368
By combining two chemical methods of purification, 4 mg of purified CeLu2N@C80 was readily isolated from 500 mg of carbon soot extract without the use of recycling HPLC, a method which has previously been necessary to obtain pure samples of endohedral fullerenes. In stage 1, CeLu2N@C80 was selectively precipitated by virtue of its low first oxidation potential (+0.01 V) and the judicious choice of MgCl2 as the Lewis acid precipitant. For stage 2, we used a stir and filter approach (SAFA), which employed the electron‐rich NH2 groups immobilized on silica gel to selectively bind residual endohedrals and higher cage fullerenes that were contaminants from stage 1. Crystallographic analysis of CeLu2N@C80 in the co‐crystal CeLu2N@Ih‐C80 ? Ni(octaethylporphyrin) ? 2(toluene) reveals that the Ih‐C80 cage is present with a pyramidalized CeLu2N unit inside. 相似文献
19.
Marc Garcia‐Borràs Dr. Sílvia Osuna Dr. Josep M. Luis Prof. Marcel Swart Prof. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7141-7154
The chemical functionalization of endohedral (metallo)fullerenes has become a main focus of research in the last few years. It has been found that the reactivity of endohedral (metallo)fullerenes may be quite different from that of the empty fullerenes. Encapsulated species have an enormous influence on the thermodynamics, kinetics, and regiochemistry of the exohedral addition reactions undergone by these species. A detailed understanding of the changes in chemical reactivity due to incarceration of atoms or clusters of atoms is essential to assist the synthesis of new functionalized endohedral fullerenes with specific properties. Herein, we report the study of the Diels–Alder cycloaddition between 1,3‐butadiene and all nonequivalent bonds of the Ti2C2@D3h‐C78 metallic carbide endohedral metallofullerene (EMF) at the BP86/TZP//BP86/DZP level of theory. The results obtained are compared with those found by some of us at the same level of theory for the D3h‐C78 free cage and the M3N@D3h‐C78 (M=Sc and Y) metallic nitride EMFs. It is found that the free cage is more reactive than the Ti2C2@D3h‐C78 EMF and this, in turn, has a higher reactivity than M3N@D3h‐C78. The results indicate that, for Ti2C2@D3h‐C78, the corannulene‐type [5, 6] bonds c and f , and the type B [6, 6] bond 3 are those thermodynamically and kinetically preferred. In contrast, the D3h‐C78 free cage has a preference for addition to the [6, 6] 1 and 6 bonds and the [5, 6] b bond, whereas M3N@D3h‐C78 favors additions to the [6, 6] 6 (M=Sc) and [5, 6] d (M=Y) bonds. The reasons for the regioselectivity found in Ti2C2@D3h‐C78 are discussed. 相似文献
20.
Orienting Effect of the Cage Addends: The Case of Nucleophilic Cyclopropanation of C2‐C70(CF3)8 下载免费PDF全文
Dr. Marina G. Apenova Olesya O. Semivrazhskaya Eugenia V. Borkovskaya Nikita M. Belov Dr. Ilya N. Ioffe Dr. Vitaliy Yu. Markov Prof. Dr. Sergey I. Troyanov Dr. Natalia S. Lukonina Prof. Dr. Lev N. Sidorov Dr. Alexey A. Goryunkov 《化学:亚洲杂志》2015,10(6):1370-1378
C2‐C70(CF3)8 was found to be a very promising substrate in the Bingel and the Bingel–Hirsch reactions combining perfect regioselectivity with much higher reactivity compared to its analogs. The reactions with diethyl malonate yield a single isomer of the monoadduct C70(CF3)8[C(CO2Et)2] and a single C2‐symmetrical bisadduct C70(CF3)8[C(CO2Et)2]2. The Bingel–Hirsch variation is particularly interesting in that it additionally affords, in a similar regioselective manner, the unexpected alkylated derivatives C70(CF3)8[CH(CO2Et)2]H and C70(CF3)8[C(CO2Et)2][CH(CO2Et)2]H. The novel compounds have been isolated and structurally characterized by means of 1H and 19F NMR spectroscopy as well as single‐crystal X‐ray diffraction. The mechanistic and regiochemical aspects of the reaction are explained with the aid of DFT calculations. 相似文献