Bond Orders and Atomic Properties of the Highly Deformed Halogenated Fullerenes C₆₀F₁₈ and C₆₀Cl₃₀ Derived from their Charge Densities

Abstract

The experimental charge densities of the halogenated C(60) fullerenes C(60)F(18) and C(60)Cl(30) were determined from high-resolution X-ray data sets measured with conventional Mo(Kalpha) radiation at 20 K for C(60)Cl(30) and with synchrotron radiation at 92 K for the fluorine compound. Bond topological and atomic properties were analyzed by using Bader's AIM theory. For the different C--C bonds, which vary in lengths between 1.35 and 1.70 A bond orders n between n=2 and significantly below n=1 were calculated from the bond topological properties at the bond critical points (BCP's). The low bond orders are seen for 5/6 bonds with each contributing carbon carrying a halogen atom. By integration over Bader's zero flux basins in the electron density gradient vector field atomic properties were also obtained. In contrast to free C(60), in which all carbon atoms have a uniform volume of 11 A(3) and zero charge, atomic volumes vary roughly between 5 and 10 A(3) in the halogenated compounds. Almost zero atomic charges are also found in the Cl derivative but a charge separation up to +/-0.8 e exists between C and F in C(60)F(18) due to the higher fluorine electronegativity, which is also seen in the electrostatic potential for which the electronegativity difference between carbon and fluorine, and the addition to one hemisphere of the fullerene cage leads to a strong potential gradient along the C(60)F(18) molecule. From the summation over all atomic volumes it follows that the halogen addition does not only lead to a dramatic distortion of the C(60) cage but also to a significant shrinkage of its volume.

Synthesis and Structure of a Highly Chlorinated C78: C78(2)Cl30

“…Shortest intermolecular Cl ··· Cl contacts are within the range of 3.13–3.42 Å. Comparatively short intermolecular Cl ··· Cl distances found in most crystal packings of fullerene chlorides [4, 5, 10–12, 14, 17] are most probably due to the very small charge on chlorine atoms being nearly zero 26. Solvated chlorine molecules occupy large tetrahedral holes in the packing of C 78 Cl 30 molecules; therefore, they are highly disordered between several positions.…”

Bindungsmuster zweier C90‐Isomere, bestimmt durch Strukturaufklärung von C90Cl32

“…Dies wurde quantitativ durch die Untersuchung der Elektronendichte von D 3d -C 60 Cl 30 bestätigt, in dem drei Typen von Cl-Atomen gefunden wurden, die mit À0.13, À0.08 und sogar + 0.06 e sehr geringe Ladungsdichten tragen. [19] …”

“…[7] So traten im Fall von C 90 , das eine "magische" 6n-Zahl von C-Atomen sowie 46 mögliche IPR-Isomere aufweist, [7,8] Unsicherheiten bei der Zuordnung von 13 C-NMR-Spektrallinien in Isomerengemischen auf. [9][10][11] Kürzlich wurde ein wahrscheinliches Additionsmuster von zwölf CF 3 -Gruppen im C 90 -Käfig (als Isomer 32 vermutet) auf Basis eines 19 F-NMR-Spektrums von C 90 (CF 3 ) 12 vorgeschlagen. [4e] Hier berichten wir über die Synthese und röntgenographische Untersuchung von C 90 Cl 32 , die die Bestimmung der Käfigstrukturen von zwei C 90 -Isomeren ermöglichte.…”

Electronic structure of the chlorinated fullerene C60Cl30 studied by quantum chemical modeling of X‐ray absorption spectra

“…Analysis of the occupation of natural orbitals in D 3d ‐C 60 Cl 30 shows a negative charges on all carbon atoms (about −0.01e) and positive charges on chlorine atoms (about +0.04e). More correct charge distribution in D 3d ‐C 60 Cl 30 molecule has been obtained using the Bader atom in molecule analysis 23. All carbon atoms bonded with chlorine were found to have positive charges varied from +0.06e to +0.18e, the bare carbon atoms (C 1 and C 2 C 3 in Fig.…”