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The redox properties of cis-[Ru(dcbpyH2)2(NCS)2] ([Ru(dcbpyH2)2(NCS)2]; dcbpyH2 = 2,2‘-bipyridine- 4,4‘-dicarboxylic acid) have been investigated in various solvents by combining electrochemical techniques (cyclic voltammetry (CV) and spectroelectrochemistry), mass spectrometry, digital simulation techniques, and semiempirical quantum chemical calculations. The electrochemical study has shown that while in polar solvents such as acetonitrile and ethanol the complex undergoes, following oxidation, the rapid loss of SCN ligands, forming the corresponding solvato complexes. In the less polar solvent tetrahydrofuran, a reversible oxidative CV behavior is observed at relatively low scan rates. On the basis of the CV and spectroelectrochemical studies and supported by quantum chemical calculations, a complex parallel ECE mechanism is proposed, comprising the loss of the SCN ligands in their pristine (anionic) form, which is initiated by the metal-centered oxidation process.

An electrochemical and EPR study is reported on two isomeric C60 derivatives containing a covalently linked free radical TEMPO:  a fulleroid and a methanofullerene. In line with other C60-based nitroxide derivatives, the latter one gives a stable biradical anion upon one-electron reduction, and a metastable excited quartet state by visible light photoexcitation. Both species have characteristic EPR spectra. For the fulleroid derivative, the first reduction step is not chemically reversible and no excited state EPR signal is observed after LASER excitation. Electrochemical and spectroelectrochemical techniques indicate that fulleroid to methanofullerene conversion takes place by photoexcitation and, more interesting, upon injection of a single electron, contrary to the cases of other fulleroids so far reported.

The electrochemistry of a benzylic amide [2]catenane was investigated and compared to that of its topologically trivial components. The redox behavior of both the catenane and the uninterlocked macrocycle can be largely understood in terms of the electrochemistry of smaller molecular fragments and simple molecular orbital considerations that show that the electroactivity of the C&dbd;O groups is split into two sets of quasi-degenerate potentials separated by a substantial gap. A fast intermolecular reaction follows the reduction of the macrocycle and smaller fragments, consistent with the corresponding dimers containing a new C−C bond linking two reduced carbonyls. The cyclic voltammetric behavior of the catenane differs significantly from that of the macrocycle&sbd;a feature that must therefore be directly attributable to the mechanically interlocked molecular architecture of the catenane. In particular, an intramolecular reaction (irreversible in the CV time scale) occurs in the catenane, which is shown to be a function of temperature and scan rate. Simulation of the cyclic voltammograms shows that the intramolecular reaction occurs on a time scale wider than that of circumrotation of the two rings in the neutral molecule, thus excluding that cyclic voltammetry (CV) is monitoring the latter process. Both the analysis of the electrochemical data and semiempirical quantum chemical (MNDO) calculations would suggest that the electrochemically induced reaction in the catenane is the soldering of the two interlocked macrocycles:  the formation of a C−C bond between two reduced carbonyl groups would thus prevent further rotation of the two interlocked rings.

The electrochemical behavior of the family of mononuclear Re(I) complexes, [Re^I(CO)3LX]ⁿ⁺, with L = 2,2‘-bipyridine (bpy), 1,10-phenanthroline (phen) and X = Cl, CN (n = 0); ACN (n = 1) and that of the metal−metal-bonded dimeric complexes [(L)(CO)3Re−Re(CO)3(L)] (L = bpy, phen) has been studied in various aprotic solvents using cyclic voltammetry (CV), chronoamperometry, and spectroelectrochemistry. The wide cathodic potential window investigated has permitted the observation of the largest number of redox processes so far obtained for these species. A detailed description of the kinetics of both oxidation and reduction processes of such species is given. The electrochemistry of the complexes [Re(CO)3(L)CN] (L = bpy, phen) is reported here for the first time. The electrochemical behavior of the monomeric species is greatly influenced by the nature of the monodentate ligand X. The concentration dependence of the cyclic voltammetric reductive behavior has evidenced the occurrence of bimolecular homogeneous processes. Such processes include homogeneous electron transfers and the competitive formation of metal−metal or μ-Cl bridged dimeric species. The influence of the solvent and that due to the presence or absence of Cl^- ions in solution is discussed. Digital simulation of the cyclic voltammetric curves is extensively used both for confirming the reaction mechanisms and for the evaluation of the relevant thermodynamic (E1/2) and kinetic parameters. Linear correlation between spectroscopic and electrochemical data for the whole family of monomeric and dimeric complexes has been found.

The electrochemical behavior of the species [Co(η⁵-C5H5)(η³-2-MeC3H4)I] and [Co(η⁵-C5H5)(η³-2-MeC3H4)(ACN)]⁺ in ACN solutions, at 25 °C, is described. The kinetic analysis of the cyclic voltammetry curves indicates that the introduction of one electron in the former complex is concerted with the dissociation of the Co−I bond. The ensuing radical undergoes fast solvation to yield the solvato complex [Co(η⁵-C5H5)(η³-2-MeC3H4)(ACN)]^•, which then acts as an efficient electron donor toward the starting material with the formation of [Co(η⁵-C5H5)(η³-2-MeC3H4)(ACN)]⁺; finally, the cation is electroreduced at the working potentials to conclude an overall autocatalytic sequence. The solvato complex [Co(η⁵-C5H5)(η³-2-MeC3H4)(ACN)]^•, formed as a product of the above reduction process, can be reversibly reduced to the corresponding anion at more negative potentials. Confirmation of the above mechanism and of the fact that the solvato complex can act as a solution electron donor toward the starting material was obtained by studying the electrochemical behavior of the solvato complex itself and through calculations aimed to better define the dissociative electron-transfer process to [Co(η⁵-C5H5)(η³-2-MeC3H4)I]. The dissociation of the metal−halide bond in the neutral complex [Co(η⁵-C5H5)(η³-2-MeC3H4)I], with the formation of [Co(η⁵-C5H5)(η³-2-MeC3H4)(ACN)]⁺, was also found to occur spontaneously, in the bulk, through the observation of a progressive change of the cyclic voltammetric pattern. Support for the occurrence of the reaction between the starting complex and the solvent was confirmed by conductivity and spectroscopic measurements, which allowed the rate constant for the homogeneous solvolysis to be determined.