Linear free energy relation of methanofullerene C61-substituents with cyclic voltammetry: Strong electron withdrawal anomaly

Keshavarz-K, Majid; Knight, Brian; Haddon, Robert C.; Wudl, Fred

doi:10.1016/0040-4020(96)00121-4

Cited by 111 publications

(88 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Despite their lower strain energy, 17 methanofullerenes can be easily reduced, as demonstrated by cyclic voltammetry experiments. 18 Both transport and spectroscopy measurements of potassium-doped methanofullerene are consistent with the splitting of the parent t 1u orbital whose magnitude increases with doping. Due to its amorphous nature, conductivity in alkali-doped methanofullerene proceeds by thermally activated hopping.…”

supporting

confidence: 53%

Optical and transport properties of an alkali-doped methanofullerene

Saab

Stucky

Srdanov

et al. 2002

The Journal of Chemical Physics

View full text Add to dashboard Cite

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. We examine the effects of monoderivatization on the electronic properties of C 60 . For this we chose the phenyl-C 61 -octanoic acid cholesteryl ester, ͓6,6͔PCOCr, whose nonlinear optical properties have been investigated in the past. While the optical absorption spectrum of this methano fullerene is similar to that of C 60 , substantial differences are observed upon doping with potassium. Similarly, the doping-dependent conductivity of the functionalized fullerene shows two maxima as opposed to the single maximum for C 60 . The experimental observations are consistent with the doping-induced degeneracy removal of the parent C 60 LUMO (t 1u ) orbital, which in potassium-doped methanofullerene splits into two components separated by about 0.5 eV. We provide experimental evidence that the doping of ͓6,6͔PCOCr proceeds, as in C 60 , with six consecutive reduction ͑electron transfer͒ steps, yielding K 6 ͓6,6͔PCOCr stoichiometry at the end. The transport in partially doped ͓6,6͔PCOCr thin films occurs by thermally activated hopping of the charge carriers with activation energy E a Х0.25 eV and hopping probability proportional to the number of unpaired electrons in the reduced molecule.

show abstract

supporting

confidence: 53%

Optical and transport properties of an alkali-doped methanofullerene

Saab

Stucky

Srdanov

et al. 2002

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…4). Among all the substituents screened, we find that SiH 2 , C(CCH) 2 and C(CN) 2 show most clearly the presence of two minima in their potential energy surface; we choose here X=C(CN) 2 as the most promising candidate since both 1c [27] and a C 60 derivative [37] have already been synthesized. We explored, therefore, the potential energy landscape for armchair CNTs in the case of C(CN) 2 cycloadditions.…”

mentioning

confidence: 99%

Cycloaddition Functionalizations to Preserve or Control the Conductance of Carbon Nanotubes

2006

View full text Add to dashboard Cite

We identify a class of covalent functionalizations that preserves or controls the conductance of single-walled metallic carbon nanotubes.[2+1] cycloadditions can induce bond cleaving between adjacent sidewall carbons, recovering in the process the sp 2 hybridization and the ideal conductance of the pristine tubes. This is radically at variance with the damage permanently induced by other common ligands, where a single covalent bond is formed with a sidewall carbon. Chirality, curvature, and chemistry determine bond cleaving, and in turn the electrical transport properties of a functionalized tube. A well-defined range of diameters can be found for which certain addends exhibit a bistable state, where the opening or closing of the sidewall bond, accompanied by a switch in the conductance, could be directed with chemical, optical or thermal means.Chemical functionalizations of carbon nanotubes (CNTs) are the subject of intensive research [1,2], and could offer new and promising avenues to process and assemble tubes, add sensing capabilities, or tune their electronic properties (e.g., doping levels, Schottky barriers, work functions, and electron-phonon couplings). However, the benefits of functionalizations are compromised by the damage to the conduction channels that follows sp 3 rehybridization of the sidewall carbons [3,4], as evidenced by absorption spectra and electrical transport measurements [5,6,7]. We report here on a class of cycloaddition functionalizations that preserves instead the remarkable transport properties of metallic CNTs. In addition, we identify a subclass of addends that displays a reversible valence tautomerism that can directly control the conductance. We focus here on [2+1] cycloaddition reactions, where the addition of a carbene or a nitrene group saturates a double-bond between two carbon atoms, forming a cyclopropane-like three-membered ring. Such functionalizations have been reported extensively in the literature [8,9,10]. All our calculations are performed using density-functional theory in the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) [11], ultrasoft pseudopotentials [12], a planewave basis set with a cutoff of 30 Ry for the wavefunctions and 240 Ry for the charge density, as implemented in quantum-espresso [13]. We examine first the simplest members in this class of addends, CH 2 and NH. Fig. 1(a) and (b) show the two inequivalent choices available on a (5,5) metallic CNT; for convenience, we label these as "S" (skewed) and "O" (orthogonal), reminiscent of the relative positions of the sidewall carbons with respect to the tube axis. Our simulation cells include 12 n carbons for a given (n,n) CNT, plus one functional group. We use a 1×1×4 MonkhorstPack mesh (including Γ) for structural optimizations, and a 1×1×8 mesh for single-point energy calculations, with a cold smearing of 0.03 Ry [14].First, and for (n,n) metallic tubes, we highlight how strongly the reaction energies of these functionalizations depend on the curvature of the nanotubes, and on their ...

show abstract

“…In the 13 C-NMR spectrum of II , the 26 sp2 signals with a characteristic intensity distribution pattern for the fullerene cage suggested that the conjugate maintained the C s symmetry (the same as that of 5 in Scheme 4). 21 The signal for the two methano-fullerene bridgehead carbons (sp3) was at 71.5 ppm, and the other carbon of the cyclopropyl ring at 52.0 ppm. The matrix-assisted laser desorption ionization – time-of-flight (MALDI-TOF) MS pattern of II was compared with the prediction on the basis of isotopic populations (IsoPro 3.0).…”

Section: Resultsmentioning

confidence: 99%

Aqueous Compatible Fullerene−Doxorubicin Conjugates

Haque

Yang

et al. 2009

J. Phys. Chem. C

View full text Add to dashboard Cite

Covalent conjugates of fullerene C 60 and the highly effective anticancer drug doxorubicin (DOX) were prepared and studied. The conjugation was through the amide linkage to preserve the intrinsic properties of DOX and fullerene cage. As designed, the conjugates with hydrophilic ethylene glycol spacers exhibited much improved aqueous compatibility, with significant solubility in water-DMSO mixtures. The anti-neoplastic activities of DOX were apparently unaffected in the conjugates according to evaluations in vitro with a human breast cancer cell line.

show abstract

Linear free energy relation of methanofullerene C61-substituents with cyclic voltammetry: Strong electron withdrawal anomaly

Cited by 111 publications

References 15 publications

Optical and transport properties of an alkali-doped methanofullerene

Optical and transport properties of an alkali-doped methanofullerene

Cycloaddition Functionalizations to Preserve or Control the Conductance of Carbon Nanotubes

Aqueous Compatible Fullerene−Doxorubicin Conjugates

Contact Info

Product

Resources

About