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A new class of dicationic ionic liquids (ILs) were synthesized for electrochemical applications at high temperatures. The syntheses are based on a dialkylation reaction of N-alkylpiperidine followed by anion exchange. The structures of ILs, based on piperidinium combined with hexafluorophosphate anion, were identified by using 1H, 13C, 19F, 31P NMR and FT-IR spectroscopy. ILs’ thermal properties were investigated in the temperature range from −50 to 350 °C by using differential scanning calorimetry (DSC). In the frequency of 10−2–106 Hz range, dielectric measurements were performed on ILs’ samples at various temperatures from −80 to 20 °C, i.e. around the glass transition temperature. The peak relaxation was observed near to this temperature. Also, the conductivity was investigated and the energy activation determined. The temperature dependence of the relaxation times was shown to be governed by the Arrhenius equation.

The inhibitive effect of the piperidin-1-yl-phosphonic acid (PPA) on the corrosion of iron in 1 M H2SO4 solution has been investigated by weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The presence of (PPA) reduces remarkably the corrosion rate of iron in acidic solution. The effect of temperature on the corrosion behavior of iron was studied in the range of 298–328 K. Results clearly reveal that the (PPA) behaves as a mixed type corrosion inhibitor with the highest inhibition at 5 × 10−3 M. The adsorption of PPA on the iron surface obeys the Langmuir's adsorption isotherm.

The inhibitive effect of the hexamethylenediamine tetra(methylene phosphonic acid) (HMDTMPA) on the corrosion of carbon steel in 1.0 M HCl solution has been investigated by weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The presence of (HMDTMPA) reduces remarkably the corrosion rate of carbon steel in acidic solution. The effect of temperature on the corrosion behavior of carbon steel was studied in the range of 298–328 K. Results clearly reveal that the (HMDTMPA) behaves as a mixed type corrosion inhibitor with the highest inhibition at 4 × 10−3 M. The adsorption of HMDTMPA on the carbon steel surface obeys to the Langmuir’s adsorption isotherm. Surface analysis via scanning electron microscope (SEM) shows a significant improvement on the surface morphology of the carbon steel plate.

The chemical and physical properties of imidazolium-based ionic liquids are determined by the interactions between the counter-ions. The C(2) position plays an important role in these interactions, as it represents the predominant site for interionic hydrogen bonding. This study shows that the directional hydrogen bonds between highly symmetrical anions (iodide, tetrafluoroborate, hexafluorophosphate) and the C(2)-H group of the 1-methyl-3-propylimidazolium cation determine the molecular and macroscopic behavior in terms of the thermal properties. Upon replacing the C(2) proton by a methyl group, the anion repositions itself at the C(4)/(5) moiety, where it forms a new hydrogen bond, apparently with only one of the two CH groups. In addition, the larger the anion is in diameter, the more likely it will establish further interactions with other parts of the cation, such as the propyl chain.

A new chelating polymeric sorbent has been developed using polystyrene resin grafted with phosphonic acid. After characterization by FTIR and elementary analysis, the new resin has been investigated in liquid-solid extraction of cadmium(II). The results indicated that phosphonic resin could adsorb Cd(II) ion effectively from aqueous solution. The adsorption was strongly dependent on the pH of the medium and the optimum pH value level for better sorption was between 3.2 and 5.2. The influence of other analytical parameters including contact time, amount of resin, metal ion concentration, and the presence of some electrolytes was investigated. The maximum uptake capacity of Cd(II) ions was 37,9 mg·g−1 grafted resin at ambient temperature, at an initial pH value of 5.0. The overall adsorption process was best described by pseudo second-order kinetic. When Freundlich and Langmuir isotherms were tested, the latter had a better fit with the experimental data. Furthermore, more than 92% of Cd(II) could be eluted by using 1.0 mol·L−1 HCl in one cycle.

Ricinine is an alkaloid of Ricinus communis that displays numerous biological properties. Ricinine (4-methoxy-1-methyl-2-oxo-dihydropyridine-3-carbonitrile)) and new N-analogues of Ricinine were obtained by the reaction of ethyl α-ethoxyethylidenecyanoacetate with various amines. Earlier, ethyl α-ethoxyethylidenecyanoacetate was easily prepared from ethyl cyanoacetate. Biologically, amines such as tryptamine and histamine were used in order to introduce a second pharmacophore on the target molecule.

In the present work, the synthesis and biological activities of substituted 2-aminopyridine δ-lactone derivatives were achieved. 4,6,6-trimethyl-2-oxo-5,6-dihydro-2H-pyran-3-carbonitrile was synthesised from 4-hydroxy-4-methylpentan-2-one, followed by its transformation in enaminonitrile with DMFDMA. The antioxidant effects of substituted 2-aminopyridine δ-lactone derivatives were evaluated through DPPH assay and revealed a great antioxidant capacity. The antifungal and antibacterial activities were investigated by disc diffusion method against clinical Gram-negative bacteria and against clinical fungi. The study shows moderate to very good antibacterial and antifungal activities for the new substituted 2-aminopyridine δ-lactone derivatives.

Purpurogallin or (6E,8Z)-2,3,4,6-tetrahydroxy-5H-benzo[7]annulen-5-one is a benzotropolone possessing a dienic system and known to inhibit the TLR1/TLR2 activation pathway. We have recently described the easy green synthesis of purpurogallin from pyrogallol catalyzed by a copper complex or by vegetable oxidases. The purpurogallin was acetylated and the tetra-acetate derivative thus obtained was engaged in a Diels–Alder reaction with various dienophiles (benzoquinone, maleic anhydride, ethylmaleimide, phenylmaleimide, etc.). The results obtained are presented and discussed.