Sc2@C70 rather than Sc2C2@C68: density functional theory characterization of metallofullerene Sc2C70

Detailed study on Sc(2)C(70) series has been performed based on fully screening for C(70) tetra- and hexa- anions. With a combined methodology of quantum chemistry and statistical mechanics, our calculation results reveal that the Sc(2)C(70), which was proposed as the first metal-carbide endohedral metallofullerene with a non-isolated pentagon rule (non-IPR) cage (Sc(2)C(2)@C(68):6073_C(2v)), is in fact a C(70) non-IPR metallofullerene structure (Sc(2)@C(70):7854_C(2v)) with three pair of pentagon adjacency thanks to its significant thermodynamic and kinetic stability. According to the natural bond analysis and orbital interaction diagram, each scandium atom should only transfer two 4s electrons to the carbon cages and the valence state of Sc(2)@C(70) is (Sc(2+))(2)@C(70) (4-). In addition, the simulation of UV-Vis-NIR spectrum for Sc(2)@C(70):7854_C(2v) shows good accordance to the experimental spectrum.     

Gd10C4Cl18 und Gd10C4Cl17, zwei Seltenerdmetall-Clusterverbindungen mit interstitiellen C2-Gruppen

Gd₁₀C₄Cl₁₈ and Gd₁₀C₄Cl₁₇, Two Lanthanoid Cluster Compounds with Interstitial C₂ Units The compounds Gd₁₀C₄Cl₁₈ ( I ) and Gd₁₀C₄Cl₁₇ ( II ) are prepared by heating stoichiometric amounts of GdCl₃, Gd, and graphite in sealed tantalum tubes at 1070 ( I ) and 1 120 K ( II ). Single crystal investigations ( I : P2₁/c, Z = 2, a = 918.2, b = 1 612.0, c = 1 288.6 pm, β = 119.86°; II : P1 , Z = 1, a = 849.8, b = 917.4, c = 1 146.2 pm, α = 104.56°, β = 95.98°, γ = 111.35°) revealed the occurrence of novel Gd₁₀C₄Cl₁₈ clusters. The metal framework is formed by edge-sharing of two Gd₆ octahedra. These are centred by C₂ units (d_{C? C} = 147 pm) and Cl atoms bridge all available edges of the octahedra. The structure of I corresponds to a packing of such quasi molecular clusters, in II they are linked to chains via common Cl atoms. Both structures are discussed in terms of a model of close packed spheres as well as in the concept of condensed clusters.     

Unprecedented mu4-C2(6-) anion in Sc4C2@C80

Metal carbide compound containing highly charged C2(q-) (q = 5, 6) moiety is rather scarce. We show by means of density functional calculations that an unprecedented mu4-C2(6-) anion can viably exist as an endohedral [Sc4C2]6+ cluster in the endofullerene Sc4C2@C80. The electronic structure, ionization energy, electron affinity, 13C NMR chemical shifts, vibrational frequencies, and electrochemical redox potentials of this unique endofullerene have been predicted to assist future experimental characterization.     

Unexpected formation of a Sc3C2@C80 bisfulleroid derivative

The reaction of tetrazine 1 with Sc(3)C(2)@C(80) exclusively affords the open-cage derivative 2 instead of the expected C(2)-inserted derivative 3 bearing a four-membered ring, as previously obtained for C(60). The structure of 2 has been firmly established by NMR spectroscopy and theoretical calculations. EPR spectroscopy shows that a single Sc atom of the Sc(3)C(2) cluster gets located within the bulge created by the bridging addend, which is a first step toward release of the internal metal atoms.     

Generation and detection of tellurane [10-Te-4(C4)] and selenurane [10-Se-4(C4)] having alkyl and aryl ligands

Formation of 2,2′-biphenylylenedimethylselenurane and -tellurane was observed by the ¹H, ¹³C, ⁷⁷Se, and ¹²⁵Te NMR studies at low temperature, in the reactions of dibenzoselenophene Se-oxide and 2,2′-biphenylylenedibromotellurane with methyllithium. These hypervalent compounds were unstable and decomposed at room temperature to give the corresponding dibenzochalcogenophenes quantitatively.     

ChemInform Abstract: The High-Temperature (β) Modification of Y4C7 with Lu4C7 Type and Dy3C4 with Sc3C4 Type Structure.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

猴金属硫蛋白突变体(N4C, T27C, N4C/T27C)的构建、表达与结构性质研究

在哺乳动物金属硫蛋白的61或62个氨基酸残基中,有20个十分保守的Acysteines,它们通常结合7个二介后过渡金属离了如ZN2+和Cd2+[1,2]等,并形成两个结构域[3],在N-端B-donain[M(I)3-Cys9]的中,3个二价后过渡金属离子均以两上端基巯基和两个桥基巯的相同方式与肽链上的半胱氨酸配位,而在C-端的a-domain[M(I)-Cys11]配位方式分为两类;两上二价后过渡金属离子分别与3个桥基巯基和1个端基配位,另两个二价后过渡金属的配位方式与中的相似,金属硫蛋白在一级序列上最显著的特征是存在多个片段,其中X是非半胱氨酸氨基酸残基[1,7].     

Structural determination of metallofullerene Sc3C82 revisited: a surprising finding

We report here the structural determination of the Sc3C82 molecule by 13C NMR spectroscopy and X-ray single-crystal structure analysis. From the present study, it is obvious that the structure of Sc3C82 is not Sc3@C82 but Sc3C2@C80.     

13C NMR spectroscopic study of scandium dimetallofullerene, Sc2@C84 vs. Sc2C2@C82

Although Sc2C84 has been widely believed to have the form Sc2@C84, the present 13C NMR study reveals that it is a scandium carbide metallofullerene, Sc2C2@C82, which has a C82(C(3v)) cage.     

The electronic structure of two novel carbides,Ca3Cl2C3 and Sc3C4, containing C3 units

The triatomic C₃ unit that is known to exist in Mg₂C₃ has recently been found in the new compounds Ca₃Cl₂C₃ and Sc₃C₄. The electronic structure of these compounds is analyzed with the aid of extended Hückel Calculation. A fragment molecular Orbital analysis (FMO) is used to study the bonding characteristic of the C₃ unit in the ionic Ca₃Cl₂C₃, and in Sc₃C₄, the latter Containing C₂ unit and single C atoms as well. Sc₃C₄ Contain partially filled Sc (d) and C₂ bands leading to Metallic conductivity and Pauli Paramagnetism. The C? C bond distance in the diatomic C₂ units is significantly increased (d_{c? c}= 125 pm) relative to C^2?₂ or acetylene, because antibonding π*_g orbitals are partially filled. The unusual bending of the C₃ unit (d_{c? c}= 134 pm) in Sc₃C₄ (175,8°) and in Ca₃Cl₂C₃ (169,0°) is likely to be a result of the packing arrangement in these structures.     

Hydrogen uptake capacity of C2H4Sc and its ions: A density functional study

We report the gravimetric hydrogen uptake capacity of C₂H₄Sc complex and isoelectronic ions using Density Functional Theory. We predict that C₂H₄Sc⁺ can bind maximum seven hydrogen molecules in dihydrogen form giving gravimetric uptake capacity of 16.2 wt %, larger by about 2 and 4 wt % than the neutral and anion, respectively. We also found that the interaction of hydrogen molecules with C₂H₄Sc⁺ ion is characteristically different than that with neutral and anion. Vibrational spectroscopic study reveals that C₂H₄Sc and isoelectronic ions are quantum mechanically stable with their characteristic change in respective identified mode. The large gravimetric H₂ uptake capacity of C₂H₄Sc⁺ is well above the target specified by Department of Energy (DOE) by 2015. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Arrhenius parameters for the reactions CH3. + C4H10 → CH4 + C4H9. and C2H5. + C4H10 → C2H6 + C4H9.

Study of n-butane pyrolysis at high temperature in a flow system allows measurement of the sum of the rate constants of the initiation reactions and of the Arrhenius parameters of the reactions Established data for k₁/k₂ allow estimation of k₁ for 951°K and this, with recent thermochemical data, yields the result log k_?1 (l.mole s^?1) = 8.5, in remarkable agreement with a recent measurement [20] but over si×ty times smaller than conventional assumption. The product k₃k₄ (l.²mole^?2s^?2) is found to be associated with the Arrhenius parameters log (A₃A₄) = 21.90 ± 0.6 and (E₃ + E₄) = 38.3 ± 2.7 kcal/mole. These values are much higher than would be e×pected on the basis of low temperature estimates. Independent evaluation gives log A₄ = 10.5 ± 0.4 (l.mole^?1s^?1) and E₄ = 20.1 ± 1.7 kcal/mole, hence log A₃ = 11.4 ± 0.8 (l.mole^?1s^?1) and E₃ = 18.2 ± 3.2 kcal/mole. These values are shown to be entirely consistent with a wide range of results from pyrolytic studies, and it is argued that they further confirm the view that Arrhenius plots for alkyl radical–alkane metathetical reactions are strongly curved, in part due to tunneling and, appreciably, to other as yet unidentified effects. Since there is published evidence that metathetical reactions involving hydrogen atoms show even greater curvature, it is suggested that this may be a characteristic of many metathetical reactions.     

Sc2C2@C80 rather than Sc2@C82: templated formation of unexpected C2v(5)-C80 and temperature-dependent dynamic motion of internal Sc2C2 cluster

Unambiguous X-ray crystallographic results of the carbene adduct of Sc(2)C(82) reveal a new carbide cluster metallofullerene with the unexpected C(2v)(5)-C(80) cage, that is, Sc(2)C(2)@C(2v)(5)-C(80). More interestingly, DFT calculations and NMR results disclose that the dynamic motion of the internal Sc(2)C(2) cluster depends strongly on temperature. At 293 K, the cluster is fixed inside the cage with two nonequivalent Sc atoms on the mirror plane, thereby leading to C(s) symmetry of the whole molecule. However, when the temperature increases to 413 K, the (13)C and (45)Sc NMR spectra show that the cluster rotates rapidly inside the C(2v)(5)-C(80) cage, featuring two equivalent Sc atoms and weaker metal-cage interactions.