Unprecedented μ4-C26- Anion in Sc4C2@C80

Kai, Tetsuya; Lü, Xin; Wang, Chunru

doi:10.1021/jp0623995

Cited by 47 publications

(48 citation statements)

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“…2d). This is a significant achievement as a non-chromatographic separation method for isolating the interesting Sc 4 C 2 @C 80 45–48 has not yet been reported.…”

Section: Resultsmentioning

confidence: 99%

Confining the spin between two metal atoms within the carbon cage: redox-active metal–metal bonds in dimetallofullerenes and their stable cation radicals

et al. 2017

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Lanthanide–lanthanide bonds are exceptionally rare, and dimetallofullerenes provide a unique possibility to stabilize and study these unusual bonding patterns. The presence of metal–metal bonds and consequences thereof for the electronic properties of M2@C82 (M = Sc, Er, Lu) are addressed by electrochemistry, electron paramagnetic resonance, SQUID magnetometry and other spectroscopic techniques. A simplified non-chromatographic separation procedure is developed for the isolation of Er2@C82 (Cs(6) and C3v(8) cage isomers) and Sc2@C82 (C3v(8) isomer) from fullerene mixtures. Sulfide clusterfullerenes Er2S@C82 with Cs(6) and C3v(8) fullerene cages are synthesized for the first time. The metal–metal bonding orbital of the spd hybrid character in M2@C82 is shown to be the highest occupied molecular orbital, which undergoes reversible single-electron oxidation with a metal-dependent oxidation potential. Sulfide clusterfullerenes with a fullerene-based HOMO have more positive oxidation potentials. The metal-based oxidation of Sc2@C82-C3v is confirmed by the EPR spectrum of the cation radical [Sc2@C82-C3v]+ generated by chemical oxidation in solution. The spectrum exhibits an exceptionally large a(45Sc) hyperfine coupling constant of 199.2 G, indicating a substantial 4s contribution to the metal–metal bonding orbital. The cationic salt [Er2@C82-C3v]+SbCl6− is prepared, and its magnetization behavior is compared to that of pristine Er2@C82-C3v and Er2S@C82-C3v. The formation of the single-electron Er–Er bond in the cation dramatically changes the coupling between magnetic moments of Er ions.

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“…2d). This is a significant achievement as a non-chromatographic separation method for isolating the interesting Sc 4 C 2 @C 80 45–48 has not yet been reported.…”

Section: Resultsmentioning

confidence: 99%

Confining the spin between two metal atoms within the carbon cage: redox-active metal–metal bonds in dimetallofullerenes and their stable cation radicals

et al. 2017

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“…14 Analogously, Sc 4 C 2 @C 80 was predicted by quantum chemical calculations to be more stable than Sc 4 @C 82 . 15 Also for this species, two low-lying isomers of similar energy have been found computationally. The Sc 4 C 2 @C 80 system has not yet been experimentally observed.…”

Section: Introductionmentioning

confidence: 84%

“…The calculated chemical shifts (d) of the endohedral carbon atoms in Sc 4 C 2 @C 80 are about 100 ppm larger than the typical range for the cage carbon atoms. 15 Large 13 C NMR shifts have been reported in some Sc 3 TC 4 compounds (T = transition metal) in the range 360-490 ppm. 18 The 13 C NMR spectrum of a third endohedral scandium fullerene, Sc 2 C 86 , contains eleven lines and corresponds to a D 2d symmetric C 84 cage.…”

Section: Introductionmentioning

confidence: 99%

Dynamics and magnetic resonance properties of Sc3C2@C80 and its monoanion

Taubert

Straka

Pennanen

et al. 2008

Phys. Chem. Chem. Phys.

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We report density functional theory (DFT) studies on the endohedral scandium carbide fullerene Sc3C2@C80 and its monoanion [Sc3C2@C80](-). The system consisting of a Sc3C2 moiety inside the Ih C80 fullerene has been studied by using first principles molecular dynamics simulations at the DFT level. On the picosecond time scale, the triangle defined by the scandium atoms is seen to jump between orientations along the equatorial six-membered ring belt of the cage. The confined carbide unit, in turn, is engaged in a flipping motion through the Sc3 plane. In contrast to the equilibrium geometry optimisations using large basis sets that predict a trigonal bipyramidal structure, a planar Sc3C2-moiety is preferred during the finite-temperature simulation. In the molecular dynamics picture, Sc3C2@C80 is best described as an equilibrium between the two static minimum structures. Calculations of the vibrational frequencies show that the earlier predicted C2 and C2v symmetric isomers are in fact saddle points, with one imaginary normal mode frequency that is related to the flipping motion of the confined carbon dimer. Reoptimisation revealed two new minimum energy structures where the C2 unit is tilted with respect to its orientation in the earlier suggested higher-symmetry structures. The nature of the bonding in the static structures of the two isomers of Sc3C2@C80 has been investigated using the electron localisation function and natural population analysis. Some increased electron pair localisation is detected on the six-membered rings closest to the Sc atoms. 13C nuclear magnetic resonance (NMR) chemical shifts have been calculated for the closed-shell monoanion of Sc3C2@C80. The 13C shifts were also calculated for Sc2C2@C84, for further comparison to experimentally measured spectra. The confined carbon atoms are strongly deshielded in these metallofullerenes, implying an incorrect earlier interpretation of the experimental 13C NMR spectrum of Sc2C2@C84. The neutral Sc3C2@C80 system with one unpaired electron is further characterised by calculating the hyperfine coupling constants, the g tensor, as well as paramagnetic NMR (pNMR) 13C shifts for both static isomers. The chemical shifts of the confined carbon atoms and the hyperfine coupling constants of all the confined atoms are strongly dependent on the conformation of the Sc3C2 moiety. Consequently, dynamical effects are expected to be important in the modelling of the magnetic properties of endohedral scandium carbide fullerenes. The two low-lying isomers have rather different pNMR 13C shifts, implying the potential of this method in structural assignment.

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“…The C 2 group in CCFs has a variable formal charge state adapting to the metal cluster composition, from (C 2 ) 2À in M 2 C 2 @C 2n to (C 2 ) 6À in Sc 4 C 2 @C 80 . 17,18 In Sc 3 C 2 @C 80 , the rst trimetallic CCF (TCCF) and the only TCCF characterized by single-crystal X-ray diffraction (SC-XRD), 19 the acetylide unit has a formal (C 2 ) 3À charge state. 20 A similar charge distribution is also proposed for Lu 3 C 2 @C 88 .…”

Section: Introductionmentioning

confidence: 99%