(19)F NMR-, ESR-, and vis-NIR-spectroelectrochemical study of the unconventional reduction behaviour of a perfluoroalkylated fullerene: dimerization of the C70(CF3)10(-) radical anion

In Situ Polymerization Synthesis of Graphdiyne Nanosheets as Electrode Material and Its Application in NMR Spectroelectrochemistry

In situ NMR spectroelectrochemistry is extremely powerful in studying redox reactions in real time and identifying unstable reaction intermediates. In this paper, in situ polymerization synthesis of ultrathin graphdiyne (GDY) nanosheets was realized on the surface of copper nanoflower/copper foam (nano-Cu/Cuf)-based electrode with hexakisbenzene monomers and pyridine. Palladium (Pd) nanoparticles were further deposited onto the GDY nanosheets by the constant potential method. By using this GDY composite as electrode material, a new NMR-electrochemical cell was designed for in situ NMR spectroelectrochemistry measurement. The three-electrode electrochemical system consists of a Pd/GDY/nano-Cu/Cuf electrode as the working electrode, a platinum wire as the counter electrode, and a silver/silver chloride (Ag/AgCl) wire as a quasi-reference electrode, which can be dipped into a specially constructed sample tube and adapted for convenient operation in any commercial high-field, variable-temperature FT NMR spectrometer. The application of this NMR-electrochemical cell is illustrated by monitoring the progressive oxidation of hydroquinone to benzoquinone by controlled-potential electrolysis in aqueous solution.

Electrochemically Induced Dimerization of p9mp-C70(CF3)12 Trifluoromethylated Fullerene

We report a comprehensive study of a novel isomer of C₇₀(CF₃)₁₂, p⁹mp-C₇₀(CF₃)₁₂, whose electrochemical behavior differs from most of the other trifluoromethylated fullerenes. The addition pattern of p⁹mp-C₇₀(CF₃)₁₂ is established by means of ¹⁹F-¹⁹F COSY NMR spectroscopy and DFT calculations. Like p⁷mp-C₇₀(CF₃)₁₀, the new isomer p⁹mp-C₇₀(CF₃)₁₂ undergoes dimerization to the [C₇₀(CF₃)₁₂]₂^2- upon single-electron reduction. The electrochemical observations are supported by the DFT calculations of dimerization energy and the temperature dependence of the CW X-band EPR spectroscopy data. Experimentally determined dimerization energies of p⁹mp-C₇₀(CF₃)₁₂^-• and p⁷mp-C₇₀(CF₃)₁₀^-• in solution are ca -8 and -26 kJ mol^-1, respectively, in good correspondence with DFT data.

Spectroelectrochemistry, the future of visualizing electrode processes by hyphenating electrochemistry with spectroscopic techniques

Reviewing the future of electrochemistry combined with infrared, Raman, and nuclear magnetic resonance spectroscopy as well as mass spectrometry.

Negatively charged singly-bonded dimers of C1-[C70(CF3)10] and bare C70 fullerene

Singly-bonded {C₇₀(CF₃)₁₀⁻}₂ and (C₇₀⁻)₂ dimers are obtained as crystalline salts allowing their molecular structure, and optical and magnetic properties to be studied.

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.

Reductive Hydrogenation of Cs -C70 (CF3 )8 and C1 -C70 (CF3 )10

CF3 -derivatized fullerenes prove once again to be promising scaffolds for regioselective fullerene functionalization: now with the smallest possible addends-hydrogen atoms. Hydrogenation of Cs -C70 (CF3 )8 and C1 -C70 (CF3 )10 by means of reduction with Zn/Cu couple in the presence of water proceeds regioselectively, yielding only one major isomer of C70 (CF3 )8 H2 and only two for C70 (CF3 )10 H2 , whose addition patterns are combined in the only abundant isomer of C70 (CF3 )10 H4 . The observed selectivity is governed by the electronic structure of trifluoromethylated substrates. Interestingly, we discovered that Clar's theory can be utilized to predict the regiochemistry of functionalization, and we look forward to testing it on forthcoming cases of derivatization of pre-functionalized fullerene building blocks.