ESR‐Vis/NIR Spectroelectrochemical Study of C₇₀(CF₃)₂^−. and C₇₀(C₂F₅)₂^−. Radical Anions

Abstract

A spectroelectrochemical study of the two isostructural asymmetric perfluoroalkyl derivatives C(1)-7,24-C(70)(CF(3))(2) and C(1)-7,24-C(70)(C(2)F(5))(2) is presented. Reversible formation of their stable monoanion radicals is monitored by cyclic voltammetry and by in situ ESR-Vis-NIR spectroelectrochemistry. The ESR spectrum of the C(70)(CF(3))(2) (-*) radical is a 1:3:3:1 quartet with a (19)F hyperfine coupling constant (a(F)) of 0.323(4) G, demonstrating that the unpaired spin is coupled to only one of the two CF(3) groups. The (13)C satellites are assigned to specific carbon atoms. The ESR spectrum of the C(70)(C(2)F(5))(2) (-*) radical is an apparent octet with an apparent a(F) value of 0.83(2) G. DFT calculations suggest that this pattern is due to the superposition of spectra for four nearly isoenergetic C(70)(C(2)F(5))(2) (-*) conformers. Time-dependent DFT calculations suggest that the NIR band at 1090 nm exhibited by both C(70)(R(f))(2) (-*) radical anions is assigned to the SOMO-->LUMO+3 transition. The analogous NIR band exhibited by the closed-shell C(70)(CF(3))(2) (2-) dianion was blue-shifted to 1000 nm.

High-temperature and photochemical syntheses of C60 and C70 fullerene derivatives with linear perfluoroalkyl chains

“…All these results clearly indicate that n = 10 is the highest As expected, PFAFs with R f > C 2 F 5 are much harder to separate than their perfluoroethyl-and TMF analogues. The tendency of decreasing retention times as the size of R f increases (for a given composition) has been noted by us earlier [33] and observed in the present study. For example, under similar HPLC conditions, C 70 (n-C 3 F 7 ) 10 isomers elute at 2.7-3.5 min whereas retention times of C 70 (C 2 F 5 ) 10 are 2.7-7.0 min [26,28].…”

“…S4-8 and S4-9 in SI). The C 70 (C 2 F 5 ) 2 isomer was studied earlier [33]. The 19 F NMR spectrum of C 70 (C 2 F 5 ) 4 -I has four narrow resonances at (Àd) 79.68, 80.05, 80.30, and 80.52 due to fluorine atoms of the four magnetically inequivalent CF 3 groups and a group of peaks in the (Àd) 110-120 region due to F(CF 2 ) atoms ( Fig.…”

“…We first examined if our suggestion that PFAFs with the same addition pattern but different R f groups would have similar redox properties. We recently demonstrated that it is the case for 7,24-C 70 (CF 3 ) 2 and 7,24-C 70 (C 2 F 5 ) 2 : their E 1/2 values were measured as 0.26 and 0.28 V vs. C 70 0/À , respectively [33]. In this study, the first peak potentials for two isomers of C 60 (C 2 F 5 ) 10 , which presumably have the same addition patterns as those of two of C 60 (CF 3 ) 10 isomers (60-10-6 and 60-10-1) were estimated as 0.44 and 0.68 V cf.…”

“…Â 250 mm) at 300 nm UV detection; the detailed procedures are described in the SI (pp.S2-S4 in SI). C 70 (C 2 F 5 ) 2 was isolated and characterized as described earlier [33]. Two isomers of C 70 (C 2 F 5 ) 4 were isolated from the high-temperature flow tube reaction product and purified in 20:80 toluene/heptane eluent at 5 mL min À1 (C 70 (C 2 F 5 ) 4 -I) and 60:40 (v:v) toluene/heptane eluent at 5 mL min À1 (C 70 (C 2 F 5 ) 4 -II), and their retention times were 24.6 and 12.8 min, respectively.…”

Crystallographic Evidence for Direct Metal–Metal Bonding in a Stable Open‐Shell La2@Ih‐C80 Derivative

“…Tr ifluoromethylation of EMFs was firstly carried out on the open-shell Y@C 82 to afford as eries of closed-shell adducts Y@C 82 (CF 3 ) n (n = 1, 3, 5) [12] with an odd number of addends. [12,[17][18][19][20][21][22][23][24][25][26] In these adducts an even number of CF 3 radicals was always attached to these fullerenes to maintain their closed-shell configurations.However,C F 3 addition normally provides mixtures with multiple CF 3 groups added to the carbon cage.T hus,p olyaddition limits the applications of this reaction and new radical reactions with high selectivity are desirable. [12,[17][18][19][20][21][22][23][24][25][26] In these adducts an even number of CF 3 radicals was always attached to these fullerenes to maintain their closed-shell configurations.However,C F 3 addition normally provides mixtures with multiple CF 3 groups added to the carbon cage.T hus,p olyaddition limits the applications of this reaction and new radical reactions with high selectivity are desirable.…”