title: [6,6]-Open and [6,6]-closed isomers of C70(CF2): synthesis, electrochemical and quantum chemical investigation.
abstract: Novel difluoromethylenated [70]fullerene derivatives, C70(CF2 )n (n=1-3), were obtained by the reaction of C70 with sodium difluorochloroacetate. Two major products, isomeric C70(CF2 ) mono-adducts with [6,6]-open and [6,6]-closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X-ray analysis and high-level spectroscopic techniques. The [6,6]-open isomer of C70(CF2 ) constitutes the first homofullerene example of a non-hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C70(CF2 ) isomers showed that it is substantially higher for the [6,6]-open isomer (the 70-electron π-conjugated system is retained) than the [6,6]-closed form, the latter being similar to the electron affinity of pristine C70. In situ ESR spectroelectrochemical investigation of the C70(CF2 ) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter-conversion between the [6,6]-closed and [6,6]-open forms of a cage-modified fullerene driven by an electrochemical one-electron transfer. Thus, [6,6]-closed C70(CF2 ) constitutes an interesting example of a redox-switchable fullerene derivative.
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1, 119991, Moscow (Russia), Fax: (+7) 495-939-1240.
authors.forename: Nataliya A
authors.initials: NA
authors.lastname: Samoylova
authors.forename: Nikita M
authors.initials: NM
authors.lastname: Belov
authors.forename: Victor A
authors.initials: VA
authors.lastname: Brotsman
authors.forename: Ilya N
authors.initials: IN
authors.lastname: Ioffe
authors.forename: Natalia S
authors.initials: NS
authors.lastname: Lukonina
authors.forename: Vitaliy Yu
authors.initials: VY
authors.lastname: Markov
authors.forename: Adrian
authors.initials: A
authors.lastname: Ruff
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Rybalchenko
authors.forename: Paul
authors.initials: P
authors.lastname: Schuler
authors.forename: Olesya O
authors.initials: OO
authors.lastname: Semivrazhskaya
authors.forename: Bernd
authors.initials: B
authors.lastname: Speiser
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Troyanov
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Magdesieva
authors.forename: Alexey A
authors.initials: AA
authors.lastname: Goryunkov
mesh_terms: D037741:Fullerenes / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D013237:Stereoisomerism
chemical_list: D037741:Fullerenes
keywords: density functional calculations; fullerenes; molecular switches; spectroelectrochemistry; structure elucidation