We report the identification and quantitative isolation of Au145(SR)60X (R = n-butyl, n-pentyl; X = halide) along with elucidation of key properties as compared to the corresponding ubiquitous chiral-icosahedral Au144(SR)60...

Five mononuclear tris‐chelate complexes of FeII, CoII, NiII and ZnII, containing the bidentate ligand 3‐methyl‐1‐(2‐pyridyl)imidazolyl‐2‐thione (L), have been synthesised and characterised, namely [MII(L)3](BF4)2, where M = Fe (1), Co (2), Ni (3) and Zn (4), and [FeII(L)3](PF6)2 {1‐(PF6)2}. The complexes have been characterised by standard methods and single‐crystal X‐ray diffraction, showing that all the complexes are isostructural and isomorphs, crystallising in the P1 space group, except for 1‐(PF6)2, which crystallises in the P21/c, as expected due to the different size and symmetry of the anion. The metal centre is found in a distorted meridional‐N3S3 octahedral geometry. In all the complexes, two ligand strands within the same complex cation unit interact via an almost perfect face‐to‐face π–π stacking. The double intramolecular interaction occurs between a pyridyl ring of one ligand strand and an imidazolyl ring of a second ligand strand and vice versa. The FeII and CoII complexes, 1 and 2, are stabilised in the high spin state, based on the bond lengths and angles obtained by SC‐XRD and by VT‐magnetic studies in the solid state and NMR Evans method in CD3CN solution. The cyclic voltammetry behaviour for compounds 1–4 showed an EC mechanism for the oxidation process, in which two ligand strands are electrochemically oxidised, instead of the metal centre, followed by a chemical process (de‐coordination and dimerisation). Whereas, the reduction process involved metal electrodeposition for the FeII, NiII and ZnII complexes. In the case of the CoII complex, the voltammetric response suggested a multistep decomposition process during the electrochemical reduction. Finally, a linear correlation between the oxidation potential of the ligand and the average M–N bond length has been found, permitting the modification of the oxidation potential by selection of the metal centre.

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The electrochemical oxidation of tetrabutylammonium carboxylates derived from 6‐oxoheptanoic acid and 6‐heptynoic acid was performed on glassy carbon electrodes to generate covalently modified electrodes bearing alkyl‐ketone and alkynyl groups. These surfaces were used as models of hydrogen‐bond‐accepting surfaces to study the interaction of water with the grafted film; 1,4‐benzoquinone was used as the redox probe to demonstrate the existence of these interactions. The voltammetric behavior of this redox probe on the modified electrode changed during cycling. However, leaving this electrode to stand in the electrolyte solution allows the recovery of the starting voltammogram. These changes observed between cycling and stand time are cyclical and can be explained through a reversible reorganization effect of the grafted film, which is attributed to hydrogen bonding interactions between the functional groups present in the structure film and water present in the solvent. Supporting these surface effects, the switching behavior was absent on hydrophobic films formed with saturated aliphatic chains or by using ferrocene as non‐hydrogen bonding redox probe.

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The anodic oxidation of tetrabutylammonium carboxylates bearing aromatic or unsaturated terminal groups is a reaction that allows the covalent grafting of organic moieties on carbon electrodes in acetonitrile as solvent. The electron transfer step is followed by a fast decarboxylation reaction, which releases the respective unsaturated free radicals, whose transient formation at the interface explain the surface grafting phenomenon, however; the lack of grafting during the oxidation of saturated aliphatic carboxylates is unexpected. Therefore, this work shows that the covalent grafting by oxidation of unsaturated carboxylates is favored for a parallel orientation of the radicals on the electrode surface, which is originated by the positive polarization of the electrode and the partially negative electronic density on the terminal unsaturated groups in the radical structure. This orientation is furthermore the result of a previous similar orientation of the unsaturated carboxylates, which is transitorily retained because of the very high rate of the decarboxylation step. Cyclic voltammetry experiments performed using different saturated and unsaturated alkyl-carboxylates, their respective carboxylic acids, as well as the use of ferrocene derivatives as redox probes were used to indirectly support the main conclusions given here.

The spontaneous decomposition of 4‐nitrophenyldiazonium tetrafluoroborate in acetonitrile solution was used to modify glassy carbon electrodes with films bearing nitrophenyl groups. The modification procedure was performed by dipping non‐connected electrodes into the nitrophenyldiazonium solution. When these modified electrodes were analyzed by cyclic voltammetry in acetonitrile containing traces of water over a wide potential scale, only one reduction wave and two oxidation peaks were observed, which is atypical considering the reversible behaviour of the reduction of nitrobenzene in acetonitrile, however in acetonitrile containing a lower concentration of water, two consecutive reduction waves appear in the same potential scale. The difference between both behaviours is consistent with the presence of water trapped into the film structure, which promotes electron and proton transfer reactions that yield nitrosobenzene as product in surface. The trapping of water inside the film structure is justified by the capability of the nitrophenyl groups to interact with water by surface hydrogen bonding interactions.