Ionic liquids from cationic palladium(II) chelate complexes: preparation, thermal properties, and crystal structures

Metal-containing ionic liquids comprising cationic Pd(II) chelate complexes and the bis(trifluoromethanesulfonyl)amide (Tf2N) anion were prepared: [Pd(acac)(Me4en)]Tf2N (1), [Pd(acac)(BuMe3en)]Tf2N (2), and [Pd(C8-acac)(Me4en)]Tf2N (3) (acac = 2,4-pentanedionate, C8-acac = 3-octyl-2,4-pentanedionate, Me4en = N,N,N',N'-tetramethylethylenediamine, BuMe3en = N-butyl-N,N',N'-trimethylethylenediamine). These salts were yellow solids with melting points of 85.2 °C, 71.1 °C, and 62.3 °C, respectively. During cooling from the liquid state, complex 1 exhibited crystallization, whereas 2 and 3 exhibited only glass transitions at approximately -40 °C. X-ray structure determination revealed that the cations in 1 and 3 form dimer-like arrangements and that there were no direct contacts between the charged moieties of the cations and anions in the solid state.

Diazopyridine–Ni(ii) complexes exhibiting intra-chain ferromagnetic interaction after irradiation: formation of magnetic gel

The gel of a diazopyridine–Ni(ii) complex in EtOH–20% CH₂Cl₂ solution showed the magnetic behavior of a ferromagnetic chain with the correlation length of 5–6 units after irradiation, suggesting the formation of magnetic gel.

Colorimetric solvent indicators based on Nafion membranes incorporating nickel(II)-chelate complexes

To develop solvent-recognition films, Nafion membranes incorporating cationic nickel-chelate complexes, that is, [Ni(L(1))(L(2))](+) (HL(1) = acetylacetone, 2,2,6,6-tetramethyl-3,5-heptanedione; L(2) = N,N-diethylethylenediamine, N-butyl-N,N',N'-trimethylethylenediamine), were prepared. Immersion of the films in various solvents effected the color changes varying from red to pale blue green depending on the donor number of the solvents. The color change is based on an equilibrium shift between square-planar and solvent-coordinated octahedral geometries of the cations. The degree of the color change depended on the affinity of the incorporated complex to the solvent molecules. The films were robust and exhibited a reversible solvent response. The films exhibited thermochromism when a small amount of appropriate solvents were incorporated and changed from pale blue green at low temperatures to red at high temperatures.