Electrochemically Induced Processes

Wohrle, D., D. Schlettwein, M. Kirschenmann, M. Kaneko, and A. Yamada (1990). The combination of phtha-locyanines and polymers for electrochemically induced processes. J. Macromol. Sci. Chem. A 27,1239-1260. 

Wang L, Kowalik J, Mizaikoff B, Kranz C (2010) Combining scanning electrochemical microscopy with infrared attenuated total reflection spectroscopy for in situ studies of electrochemically induced processes. Anal Chem 82 3139-3145... 

One aspect that reflects the electronic configuration of fullerenes relates to the electrochemically induced reduction and oxidation processes in solution. In good agreement with the tlireefold degenerate LUMO, the redox chemistry of [60]fullerene, investigated primarily with cyclic voltammetry and Osteryoung square wave voltammetry, unravels six reversible, one-electron reduction steps with potentials that are equally separated from each other. The separation between any two successive reduction steps is -450 50 mV. The low reduction potential (only -0.44 V versus SCE) of the process, that corresponds to the generation of the rt-radical anion 131,109,110,111 and 1121, deserves special attention. 

It should be emphasized that the majority of electrochemically induced redox processes in inorganic chemistry proceed (or are assumed to proceed) through outer-sphere mechanisms. 

The first is the catalytic efficiency of the electrocatalytic process, which in the case of the electrochemically induced reaction is called coulombic efficiency. It is determined by the number of product molecules formed per electron consumed. In our example, the consumption of 0.02 electrons per molecule indicates a coulombic efficiency of 50 molecules produced per electron consumed. 

At this point, it is important to indicate that a very large number of C-bridged cyclopropanated fullerene derivatives undergo irreversible reduction processes leading to the removal of the addend and recovery of the pristine parent fullerene. The process has been advantageously used in electrosynthetic procedures, and thus a separate section covering the electrochemically induced retro-cyclopropanation reaction is presented later in this chapter (see Sect. 6.1.5.2). A number of other C-bridged cyclopropanated derivatives will be discussed there. 

Electroswitching of structure takes place when a redox change induces a reversible structural or conformational process in a molecule, such as an electrochemically activated intramolecular rearrangement [8.259]. On the supramolecular level it consists of the electroinduced interconversion between two states of different superstructure. A case in point is the reversible interconversion of a double-helical dinuclear Cu(l) complex M2L22+ [8.260] and of a mononuclear Cu(ll) complex ML2+ in a sequential electrochemical-chemical process [8.261] ... 

In 2006, electrochemically induced synthesis of (3-lactams, by cyclization of haloamides, has been achieved in suitable solvent-supporting electrolyte solutions previously electrolyzed under galvanostatic control [166, 167]. The yields and the stereochemistry of the process were influenced by the nature of the R -R4 substituents, by the solvent-supporting electrolyte solutions, and by the electrolysis conditions (Scheme 69). 

Other methanofullerenes (not of the Bingel-type) were also found to be unstable after several reduction processes (68-70, Figure 23), [9-11] and under CPE they led to the isolation of [60]fullerene. A more recent study was conducted in THF to avoid the well-known reactivity of CH2CI2 towards the polyanions of C60 [72] and to explore the mechanisms involved during adduct removal [9b,10], Surprisingly, an electrochemically induced intermolecular adduct transfer was observed for the spiromethanofullerenes studied, and the regio-isomer distribution found in THF differed significantly from that obtained when the compounds are prepared by a direct synthetic route [10], The proposed mechanism for the formation of... 

---