Daria V. Ignat'eva

Preparation, crystallographic characterization and theoretical study of two isomers of C70(CF3)12

Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers.

Trifluoromethylation of fullerenes: kinetic and thermodynamic control.

We present a survey and theoretical interpretation of the experimental results on trifluoromethylation of fullerenes. A thermodynamic model has been developed to describe the C60/70(CF3)n condensed phase mixtures capable of free exchange of addends and, consequently, of isomerization and changing the degrees of addition. It was found that the purely thermodynamic model affords at least satisfactory prediction of composition of products even for apparently nonequilibrium syntheses. Special cases can be identified by means of detailed kinetic modeling based on the BEP approach, which includes stepwise energetic analysis of the possible trifluoromethylation sequences. This analysis reveals two types of reactions with remarkable difference in rates: direct trifluoromethylation and rearrangements of the CF3 groups. Whenever a particular group of compounds is interrelated through direct addition/abstraction of CF3 groups, it is more or less safe to assume that the said group is in equilibrium describable by the thermodynamic model. In the same time, the slower migration of addends is controlled kinetically, and interference of the sublimation processes frequently prevents its equilibration. Among the most illustrative examples of hindered formation via rearrangements in absence of sufficiently favorable direct trifluoromethylation pathways are certain isomers of the C3v-C60(CF3)18, C70(CF3)18, and C70(CF3)20 compounds.

Isolation and structural characterization of the most highly trifluoromethylated C70 fullerenes: C70(CF3)18 and C70(CF3)20

One isomer of C70(CF3)18 and two isomers of C70(CF3)20 have been isolated from the products of the trifluoromethylation of C70; their molecular structures were determined by single crystal X-ray crystallography and are discussed in terms of their addition patterns and relative formation energies.

Chlorination‐promoted Transformation of Isolated Pentagon Rule C78 into Fused‐pentagons‐ and Heptagons‐containing Fullerenes

Cage transformations in fullerenes are rare phenomena which are still not fully understood. We report the first skeletal transformation of an Isolated-Pentagon-Rule (IPR) isomer of C78 fullerene upon high-temperature chlorination which proceeds by six-step Stone-Wales rearrangements affording non-IPR, non-classical (NC) C78 (NC2)Cl24 with two cage heptagons, six pairs of fused pentagons, and an unprecedented loop-like chlorination pattern. The following loss of a C2 unit results in C76 (NC3)Cl24 containing three cage heptagons.

Synthesis, Isolation and Structure of Trifluoromethylated Fullerene D3-C78, C78(1)(CF3)10−18

High-temperature trifluoromethylation of fullerene C78 followed by HPLC separation of C78 (CF3)n derivatives resulted in the isolation and X-ray structural characterization of 15 compounds, that is, two C78(1)(CF3)10, three C78 (1)(CF3)12, four C78 (1)(CF3)14, and five C78 (1)(CF3)16 isomers as well as one isomer of C78(1)(CF3)18. The addition patterns of the C78(1)(CF3)n molecules are discussed in terms of trifluoromethylation pathways and relative formation energies.

Synthesis, Isolation and Structures of Trifluoromethylated Fullerenes D 2-C76, C76(1)(CF3)10-18

High-temperature trifluoromethylation of fullerene C76 chlorination products followed by HPLC separation of C76 (CF3 )n derivatives resulted in the isolation and X-ray structural characterization of thirteen C76 (1)(CF3 )n compounds including nine new isomers such as one isomer of C76 (1)(CF3 )10 , two C76 (1)(CF3 )12 , three C76 (1)(CF3 )14 , one C76 (1)(CF3 )16 , and two isomers of C76 (1)(CF3 )18 . Depending on their addition patterns, C76 (1)(CF3 )n isomers are divided into three subgroups and discussed in terms of trifluoromethylation pathways and relative formation energies.