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[en] Highlights: • Electrospray ionization mass spectrometry was used for characterization of cation-π interaction. • Cation Li+ forms with helicene (C26H16) the “asymmetrical” complex [Li(C26H16)]+. • By employing DTF calculations, the most probable structure of the proven cation-π complex [Li(C26H16)]+ was predicted. By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the lithium cation (Li+) forms with racemic helicene (C26H16) the cationic complex species [Li(C26H16)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C26H16)]+ complex was derived. In the resulting “asymmetrical” complex, the “central” cation Li+ is bound by six bonds to six carbon atoms from the two terminal benzene rings of the parent helicene ligand via cation-π interaction. Finally, the interaction energy, E(int), of the considered cation-π complex [Li(C26H16)]+ was found to be −248.0 kJ/mol, confirming the formation of this cationic complex species as well.
[en] Solid complexes formed between Poly (ethylene oxide) and various alkali metal salts, are generally referred to as polymer electrolytes conductivity and NMR properties were investigated in POE - Li Cl sub(7)O sub(4) and POE - Li BF sub(4) complexes. Our sup(1)H, Li and sup(19)F relaxation study suggest that cation motion is controlled by segmental motions of the polymer chain while the anion have additional mobility associated with BG sub(4) rotation. (author)
[en] The new compounds LiK[C(CN)3]2 and Li[C(CN)3] . 1/2 (H3C)2CO were synthesized and their crystal structures were determined. Li[C(CN)3] . 1/2 (H3C)2CO (H3C)2CO crystallizes in the orthorhombic space group Ima2 (no. 46) with the cell parameters a=794.97(14), b=1165.1(2) and c=1485.4(3) pm, while LiK[C(CN)3]2 adopts the monoclinic space group P21/c (no. 14) with the cell parameters a=1265.7(2), b=1068.0(2) and c=778.36(12) pm and the angle β=95.775(7) . Single crystals of K[C(CN)3] were also acquired, and the crystal structure was refined more precisely than before corroborating earlier results.
[en] The catalytic oxidation of dopamine (DA) at a LiTCNE (lithium tetracyanoethylenide) film modified electrode is studied by electrochemical approaches. The immobilization of LiTCNE was performed by a polymer (poly-L-lysine) to prepare this modified electrode and its application for dopamine (DA) determination is described in detail. The modified electrode showed a high activity for the electrooxidation of dopamine (DA) at E p 0.20 V versus SCE. The modified electrode presented a wide linear response range for DA from 0.01 up to 10 μmol l-1 by differential pulse voltammetry (DPV) with a detection limit of 0.5 nmol l-1. The repeatability of the proposed sensor evaluated in term of relative standard deviation was 3.2% for n = 10. The sensor was applied for the determination of dopamine in pharmaceutical formulations and the average recovery for these samples was 101.9 (±0.1)%