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A panel of dicationic ionic liquids (DILs) with different rigid xylyl (ortho, meta, para) spacers and different anions (bromide and tungstate) has been synthetised and characterised through different experimental and computational techniques. Differences and analogies between the systems are analysed using information derived from their DFT structures, semiempirical dynamics, thermal behaviour, and catalytic properties versus the well-known reaction of CO2 added to epichlorohydrin. A comparison between the proposed systems and some analogues that present non-rigid spacers shows the key effect displayed by structure rigidity on their characteristics. The results show an interesting correlation between structure, flexibility, properties, and catalytic activity. [ABSTRACT FROM AUTHOR]

A panel of novel vanadium(IV)–betaine complexes has been synthesized according to new and efficient methodologies and characterized through both spectroscopic techniques and thermal analyses. Vanadium(IV)–betaine solutions have been electrochemically oxidized and the effect of betaine ligands on the thermal and pH stability of vanadium(V) solutions has been evaluated under different temperature and acidity conditions. The obtained results displayed a remarkable effect for both of the examined parameters, achieving the preparation of aqueous vanadium(V) solutions displaying long term stability at more than 55 °C under mild acidic conditions. The species formed in the betaine rich vanadium(V) solutions have been sprectroscopically identified in relationship with the acidity of the solution, and the obtained results were confirmed through computational techniques. Vanadium–betaine based solutions have been finally tested in a lab-scale redox flow battery setup, providing preliminary insight into the possible use of this type of electrolyte in VRFBs. [ABSTRACT FROM AUTHOR]

Two couples of dicationic ionic liquids, featuring pyrrolidinium and piperidinium cations and different linker chains, were prepared and characterized. 1,1′-(propane-1,3-diyl)bis(1-methylpyrrolidinium) bromide, 1,1′-(octane-1,8-diyl)bis(1-methylpyrrolidinium) bromide, 1,1′-(propane-1,3-diyl)bis(1-methylpiperidinium) bromide, and 1,1′-(octane-1,8-diyl)bis(1-methylpiperidinium) bromide were synthesized in quantitative yields and high purity and thermally characterized through TGA and DSC analysis. In this study, we propose a preliminary comparative evaluation of the effect of the linker chain length and of the size of the aliphatic ammonium ring on the thermal and solubility properties of bromide dicationic ionic liquids. [ABSTRACT FROM AUTHOR]

Solvatochromic probes are often used to understand solvation environments at the molecular scale. In the case of ionic liquids constituted by an anion and a cation, which are designed and paired in order to obtain a low melting point and other desirable physicochemical properties, these two indivisible components can interact in a very different way with the probe. This is the case with one of the most common probes: Reichardt's Dye. In the cases where the positive charge of the cation is delocalized on an aromatic ring such as imidazolium, the antibonding orbitals of the positively charged aromatic system are very similar in nature and energy to the LUMO of Reichardt's Dye. This leads to an interesting, specific cation-probe interaction that can be used to elucidate the nature of the ionic liquids' cations. Parallel computational and experimental investigations have been conducted to elucidate the nature of this interaction with respect to the molecular structure of the cation. [ABSTRACT FROM AUTHOR]

An efficient synthesis of symmetrical 1,2-disubstituted 4,5- dialkynylimidazoles by Sonogashira alkynylation of the corresponding 4,5-dibromo derivatives was developed. Moreover, through a careful tuning of the palladium ligand, unsymmetrical 1,2-disusbtituted 4,5-dialkynylimidazoles were also prepared through a regioselective C5 alkynylation of 4,5-dibromoimidazoles, followed by a second alkynylation involving the 4-bromo derivatives so obtained. This interesting class of imidazole-fused enediynes is also able to give thermal Bergman cycloaromatization (BC), as proved by DSC experiments. [ABSTRACT FROM AUTHOR]

Benzimidazole dicationic ionic liquids (BDILs) have not yet been widely explored in spite of their potential. Therefore, two structurally related families of BDILs, paired with either bromide or bistriflimide anions and bearing alkyl spacers ranging from C3 to C6, have been prepared. Their thermal properties have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), while their electrical properties have been assessed by cyclic voltammetry (CV). TG analysis confirmed the higher stability of the bistriflimide BDILs over the bromide BDILs, with minor variation within the two families. Conversely, DSC and CV allowed for ascertaining the role played by the spacer length. In particular, the thermal behavior changed dramatically among the members of the bistriflimide family, and all three possible thermal behavior types of ILs were observed. Furthermore, cyclic voltammetry showed different electrochemical window (C3(C1BenzIm)2/2Tf2N < C4(C1BenzIm)2/2Tf2N, C5(C1BenzIm)2/2Tf2N < C6(C1BenzIm)2/2Tf2N) as well as a reduction peak potential, shape, and intensity as a function of the spacer length. The results obtained highlight the benefit of accessing a more structurally diverse pool of compounds offered by dicationic ILs when compared to the parent monocationic ILs. In particular, gains are to be found in the ease of fine-tuning their properties, which translates in facilitating further investigations toward BDILs as designer solvents and catalysts. [ABSTRACT FROM AUTHOR]