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The cyclic voltammetry of a series of soluble N-methylfulleropyrrolidinium salts shows that these materials are better electron-acceptors than unmodi®ed C60. The stability of mono-reduced, zwitterionic, and doubly-reduced anionic species, produced either electrochemically or chemically, has been checked by absorption spectroscopy. Langmuir±Blodgett (LB) layers of the C60 derivatives mixed with tricosanoic acid have been built up on different substrates. The optical properties of the ®lms have been characterized using absorption spectroscopy and their structure was investigated by X-ray diffraction.

9,10-Bis(cyclopentadienylmethyl)anthracene (1) is obtained by reacting 9,10-bis(bromomethyl) anthracene with cyclopentadienylsodium and transformed into its dithallium(I) derivative 3 on reaction with thallium ethoxide. The reaction of 3 with the chloro derivatives of rhodium(I) of formula [RhClL2]2 (L ) è2-C2H4 or CO; L2 ) è4-C7H8) leads to the corresponding bimetallic complexes [L2Rh{C5H4CH2(9,10-anthrylene)CH2C5H4}RhL2], 4 (L ) è2-C2H4), 5 (L ) CO), and 6 (L2 ) è4-C7H8), in 13, 22, and 55% yields, respectively. All complexes have been characterized by elemental analysis, particle beam mass spectrometry, 1H NMR, and FT-IR. The UV-vis spectra (280-800 nm) of 4-6 are indicative of the existence of strong electronic interactions among the anthrylic chromophore and the two cyclopentadienylRhL2 moieties. When excited at ca. 370 nm, 1 becomes an efficient light-emitting molecule, while 4-6 are poorly luminescent compounds. The fluorescence spectra of all the complexes present the vibrational structure typical of the anthrylic fluorophore but have low intensity: 6, 3, and 15% of the one observed for 9-methylanthracene, taken as the reference compound, respectively for 4, 5, and 6. The study of the electrochemical behavior of 4-6 in strictly aprotic conditions allows a satisfactory interpretation of the observed electrode processes and furnishes information about the location of the redox sites along with the thermodynamic characterization of the corresponding redox processes. These data show that the occurrence of an intramolecular charge-transfer process between the photoexcited 9,10-anthrylenic moiety and the cyclopentadienylRhL2 unit is a possible route for the observed quenching of emission in the compounds 4-6. The one-electron oxidation of compounds 4-6 by thallium(III) trifluoroacetate in a 1:1 dichloromethane/1,1,1,3,3,3- hexafluoropropan-2-ol mixture leads to the formation of the corresponding radical cations [L2Rh{C5H4CH2(9,10-anthrylene)CH2C5H4}RhL2]+. Two of them, i.e., 4+ (L ) è2-C2H4) and 5+ (L ) CO), give rise to highly resolved EPR spectra which allow one to describe such species as average-valence [Rh+1/2, Rh+1/2] complexes. DFT calculations of spin density distribution confirm the EPR results and allow a further insight into the structure of 4+ and 5+ complexes.

The behaviour of chloranilic acid on mercury electrodes has been investigated by linear potential-sweep voltammetry. In very dilute solutions, a single adsorption peak appears. In more concentrated solutions, a second peak is observed which is diffusion-controlled. The amount of chloranilic acid adsorbed at the different concentrations has been determined by extrapolation, from the plots of the integrals of the current-potential curves versus the reciprocal of the square-root of potential-sweep rate. The maximum surface coverage thus derived is in very good agreement with the surface excess obtained from measurement of the mercury-solution interface tension using the drop-weight method. The results are consistent with the hypothesis of the formation of a monolayer of chloranilic acid with a flat orientation of the molecule with respect to the electrode surface.

Summary A drop volume method is described for the determination of the interfacial tension in conditions of adsorption equilibrium by means of a hanging mercury drop electrode. The results obtained in the study of an adsorption system characterized by a slow establishment of the adsorption equilibrium are reported and compared with those obtained with the dropping mercury electrode.

Riassunto Nel quadro delle ricerche in corso sulle relazioni fra la struttura delle soluzioni elettrolitiche e le loro manifestazioni spettroscopiche, sono stati esaminati gli spettri ultrarossi di soluzioni acquose di acido cloridrico e acido solforico a varie concentrazioni. I risultati vengono discussi anche in base al confronto di quanto osservato in Raman sulle stesse soluzioni.

IT has already been reported that aminoacetonitrile (AAN) protects the rat's liver against the necroses caused by carbon tetrachloride1–3, allylamine4, bromobenzene5, chloroform6 or dimethylnitrosamine6, whereas it is ineffective against necroses induced by thioacetamide and tannic acid5.

The electrochemical properties of a fullerene–ferrocene liquid crystal are reported. The electrochemical study was carried out under strictly aprotic conditions: a total of seven reduction peaks were detected in the negative potential region, and two oxidation peaks in the positive potential one. Comparison of the data with those obtained from suitable model compounds (i.e., analogous fullerene- or ferrocene-free materials ) has allowed the assignment of all reduction and oxidation steps. The CV study evidenced the occurrence of a fast follow-up chemical reaction coupled to the third (at 25 °C) or fourth (at –60 °C) reduction of either 1 or 3. Such a reaction, presumably related to the cleavage of one of the cyclopropane bonds, is quantitatively reversed upon re-oxidation. Conversely, under bulk electrolysis conditions (second reduction), the species undergo the retro-Bingel reaction, i.e. the irreversible removal of the bis(alkoxycarbonyl)methano adducts to give the parent C60.

1,3-Dipolar cycloaddition of azomethine ylides to C 60 generates a family of fullerene derivatives, colloquially termed fulleropyrrolidines. In this paper, we report the synthesis and the electrochemical properties of fulleropyrrolidine and fulleropyrrolidinium ion derivatives. Cyclic voltammetry measurements, performed using ultramicroelectrodes at −60°C with scan rates as high as 50 V/s, allowed, for the first time in fullerene derivatives, the observation of six fullerene-centered reductions. These derivatives also exhibit enhanced electron-accepting properties with respect to both the parent fulleropyrrolidine derivatives and C 60 . Bulk electrolysis carried out at the stage of the first reduction potential, gives rise to a stable zwitterion, with both anion and cation located on the fullerene derivatives.

Electrochemical, quantum chemical, and spectroscopic techniques are used to study the dynamics of the reduction of bpy-C{sub 61}. A thorough investigation of the temperature and scan rate dependence of the cyclic voltammetry peaks coupled with numerical simulations clearly reveals that the trianion and the tetraanion undergo two chemical reactions according to the same parallel ECE mechanism. Quantum chemical calculations show that three isomers are quasi equienergetic in the charged states and support the hypothesis that triply and quadruply reduced bpy-C{sub 61} undergoes facile conversion among three of its structural isomers, i.e., [5,6]-closed bpy-C{sub 61}, [5,6]-open bpy-C{sub 61}, and [6,6] closed bpy-C{sub 61}. Substituent and/or solvent effects may effectively reverse the roles of [5,6]-closed bpy-C{sub 61}, and [6,6]-closed bpy-C{sub 61}. As for [5,6]-closed isomer, it is the first time that its existence is proposed on the basis of the observation of a redox process. The six reduction peaks of C{sub 60} have been observed for the first time in a pure solvent (THF, - 60{degree}C), and the cyclic voltammetry peaks of the fullerene moiety and the bpy fragment have been assigned. 17 refs., 7 figs., 1 tab.

The cyclic voltammetric (CV) study of a series of novel bisfulleropyrrolidines (3) and bisfulleropyrrolidinium ions (4) is reported. The eight possible stereoisomers of each series were systematically investigated under strictly aprotic conditions that allowed the observation of up to four and five subsequent reversible reductions in 3 and 4, respectively. Because of the stabilizing effect of positive charges, a significant enhancement of the electronegative properties was observed in 4. In fact, 4-trans-2 and 4-trans-1 result among the strongest reversible electron-accepting C(60) oligoadducts. Furthermore, the study evidenced that, in both 3 and 4, the CV pattern, and in particular the potential separation between the second and third reductions, changes significantly with the addition pattern. A sequential pi-electron model that simulates the effect of subsequent reductions of C(60) bis-adducts gives a good correlation (r > 0.96) with the cyclic voltammetry data when the molecules are divided in two sets dependent on the location of the addends in the same or in opposite hemispheres.

A novel biosensor for the amperometric detection of glutathione is proposed in which glutathione reductase is coupled to a pyrrolofullerene bis-adduct playing the role of redox mediator between electrode and enzyme. The adoption of a simple procedure for realizing the immobilization of the redox mediator, together with the enzyme, within a polypyrrole film cast onto a glassy carbon electrode, was made possible by the amphiphilic properties of the fullerene derivative. The biosensor showed a fast and reproducible response to glutathione and, because of its lower sensitivity, a wider linear range with respect to a similar device based on a diffusional redox mediator.

The family of fullerene derivatives obtained by 1,3-dipolar cycloaddition of azomethine ylides to C 60 is colloquially termed fulleropyrrolidines. In this paper, we report the synthesis and the electrochemical properties of a series of fulleropyrrolidine derivatives. All compounds are characterized by the presence of a solubilizing mTEG group. In addition, a derivative containing a thiophene moiety, covalently attached to the pyrrolidine ring has been studied. Cyclic voltammetry measurements, performed also at low temperatures, allowed the observation of five fullerene-centered reductions for all the species. Adsorption phenomena, however, were found associated to the last reduction processes in the thiophene–fulleropyrrolidine conjugate. Moreover, thanks to the increased solubility of the latter species in polar solvents (acetonitrile–dichloromethane mixtures) its anodic polymerization was carried out, leading to a conducting film still retaining the redox properties of the fullerene derivative.

Synthesis and chemical properties of a novel fullerene-porphyrin dyad is reported. Energy/electron transfer is studied based on cyclic voltametry and UV-visible spectroscopy.

A novel fullerene–Ru–porphyrin conjugate (3b) for Langmuir–Blodgett (LB) film deposition has been synthesized. The side polar chain that characterizes the complex is necessary to introduce enough amphiphilicity in these otherwise non-polar moieties. The complex can be deposited on solid substrates via the LB technique and the films obtained show charge separation upon light irradiation. In addition, a careful cyclic voltammetry study of the complex is reported.