Unexpected Isomerism incis-2 Bis(pyrrolidino)[60]Fullerene Diastereomers

Facile Separation, Spectroscopic Identification, and Electrochemical Properties of Higher Trifluoromethylated Derivatives of [70]Fullerene

We survey the structure and electronic properties of the family of higher trifluoromethylated C70 (CF3 )n molecules with n=14, 16, 18, and 20. Twenty-two available compounds, of which thirteen are newly obtained and characterized, demonstrate the broad diversity of π-system topologies, which enabled us to study the interplay between the CF3 addition pattern and the electronic properties. UV/Vis spectroscopic and cyclic voltammetric studies demonstrate the importance of the exact addition pattern rather than the plain number of addends. Of particular interest is the skew pentagonal pyramid (SPP) addition pattern, which enables formation of closed-shell cyclopentadienyl anions C70 (CF3 )n-1- through CF3 detachment upon electron transfer. A detailed study of the process is presented for a SPP-C70 (CF3 )16 where potentiostatic electrolysis at the second reduction potential gives C70 (CF3 )15- oxidizable to a persistent C70 (CF3 )15. radical. Together with the literature data for the lower C70 (CF3 )n compounds with n=2-12, the present results show good correlation between the experimental boundary level positions and the DFT predictions. The compounds turn out to be electron acceptor molecular semiconductors with experimental LUMO energies and HOMO-LUMO gaps within the ranges of -4.3 to -3.7 eV and 1.6 to 3.3 eV, respectively, depending on the shape of the conjugated fragments. The HOMO levels fall within the range of -5.6 to -6.9 eV and show linear correlation with the number of addends.

Rigid Tether Directed Regioselective Synthesis and Crystallographic Characterization of Labile 1,2,3,4-Bis(triazolino)[60]fullerene and Its Thermolized Derivatives

Labile bis-triazoline adducts of C60 are supposed to be the precursors of bis-azafulleroids, but the formation mechanism is still unclear because of the incomplete isolation of the thermolized products and the lack of X-ray structures. A rigid-tethered reagent 1,2-bis(azidomethyl)benzene (1) was used to regioselectively synthesize the labile 1,2,3,4-bis(triazolino)[60]-fullerene (2), the structure of which was determined by single-crystal X-ray crystallography. Further thermolysis of 2 produces four products (3 a-3 d), which were all characterized by X-ray crystallography. Although 3 a and 3 b have traditional bis-azafulleroid structures, as proposed previously, 3 c and 3 d show unprecedented structures with either the coexistence of [5,6]-open and [6,6]-closed patterns or an oxidized structure with an 11-membered ring on the cage. A thermolysis mechanism is proposed to clarify long-term confusion about the transformation process from bis-triazoline adducts to bis-azafulleroids of C60 .

High-yield, regiospecific bis-functionalization of C70 using a Diels–Alder reaction in molten anthracene

A regiospecific bis-adduct of C₇₀ with anthracene was prepared with unusually high yield (68%) by the Diels–Alder reaction in the absence of solvent (melt). The structure of the bis-adduct was an unexpected 12 o'clock isomer, as determined by single crystal X-ray diffraction, thermal gravimetric analysis (TGA) and spectroscopy.