Carbon nano-onions (NCNOs), concentrically multilayered fullerenes, are among the least studied carbon allotropes. NCNOs have high surface area, high mesoporosity, facile electrical conductivity, and electrochemical stability. NCNOs are chemically oxidized (ONCNOs) to introduce hydrophilic functional groups, improving their wettability for use in supercapacitor electrodes. RuO2·xH2O/ONCNOs composites are prepared by chemical precipitation of RuO2 on ONCNOs, optimized for homogeneous distribution and maximum utilization of the metal oxide nanoparticles. The materials are characterized by high-resolution transmission electron microscopy, N2 absorption–desorption isotherm, and thermogravimetric analysis. Electrochemical performance of the electrodes is studied by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance measurements in 1.0 M H2SO4. While ONCNOs have specific capacitance of 45 F·g–1, a composite with 67.5 wt.% RuO2 has specific capacitance of 334 F·g–1 at a potential sweep rate of 20 mV·s–1 with high power (242.8 kW·kg–1) and high energy density (11.6 Wh·kg–1). Both the ONCNO and the composites show excellent capacitance behaviors even at very high potential scan rates (>8 V·s–1). Simple preparation of high-purity NCNOs and excellent electrochemical behavior of functionalized NCNOs make them a promising electrode material in supercapacitor applications.

The dehydration of 1′,2′,3′,4′,5′-pentamethylruthenocene-1,2-dicarboxylic acid with acetic anhydride gives 1′,2′,3′,4′,5′-pentamethylruthenocene-1,2-dicarboxylic anhydride, the first crystallographically characterized, metallocene-fused carboxylic anhydride. Treatment of the diacid with oxalyl chloride/DMF produces its 1,2-diacyl chloride, which is an excellent precursor for AlCl3-promoted double Friedel–Crafts acylation reactions with a variety of arenes, including benzene, toluene, o-xylene, p-dimethoxybenzene, and ferrocene. X-ray structural determinations of an acenequinone and a unique ferrocene/ruthenocene-fused benzoquinone show distortions attributed to strong electron donation from pentamethylruthenocene.

Reactions of the transition metal halide complexes [MXL2(Cp)] (M = Fe, X = I, L2 = dppe; M = Ru, X = Cl, L = PPh3; M = Os, X = Br, L = PPh3; Cp = η-C5H5) with the alkynol HC≡CCH(OH)(Fc) (1) (Fc = ferrocenyl) in the presence of TlBF4 gave the monosubstituted allenylidene complexes [M(C═C═CHFc)L2(Cp)][BF4] (2a: M = Ru, L = PPh3; 3: M = Fe, L2 = dppe; 4: M = Os, L = PPh3). Similarly, the reaction of 1 with [RuCl(PPh3)2(Cp)] and NH4PF6 in methanol gave [Ru(C═C═CHFc)(PPh3)2(Cp)][PF6] (2b). These highly colored compounds were characterized by spectroscopic and electrochemical techniques and in the case of 2b by a single-crystal X-ray structure determination. Cyclic voltammetry in MeCN in the presence of [nBu4N][ClO4] at 100 mV·s−1 shows a reversible ferrocenyl-based one-electron oxidation, in addition to irreversible oxidation and reduction processes. The NMR spectra of 2b show complex behavior at low temperature, attributed to temperature-dependent chemical shifts and correlated motions of the allenylidene ligand and the ferrocenyl substituent.