Tetrachloridocuprates(II)—Synthesis and Electron Paramagnetic Resonance (EPR) Spectroscopy

Abstract

Ionic liquids (ILs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., synthesis of particles, magnetic or thermochromic materials. We present the synthesis and the results of electron paramagnetic resonance (EPR) spectroscopic analyses of a series of some new potential ionic liquids based on tetrachloridocuprates(II), [CuCl4]2−, with different sterically demanding cations: hexadecyltrimethylammonium 1, tetradecyltrimethylammonium 2, tetrabutylammonium 3 and benzyltriethylammonium 4. The cations in the new compounds were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. The EPR hyperfine structure was not resolved. This is due to the exchange broadening, resulting from still incomplete separation of the paramagnetic Cu(II) centers. Nevertheless, the principal values of the electron Zeemann tensor (g║ and g┴) of the complexes could be determined. Even though the solid substances show slightly different colors, the UV/Vis spectra are nearly identical, indicating structural changes of the tetrachloridocuprate moieties between solid state and solution. The complexes have a promising potential e.g., as high temperature ionic liquids, as precursors for the formation of copper chloride particles or as catalytic paramagnetic ionic liquids.

Coordination of new disulfide ligands to CuI and CuII: Does a CuII μ-thiolate complex form?

“…[Cu II 4 (L1) 2 (Cl) 4 , which is expected to be around 400 nm, is not observed [22][23][24]. This indicates that in solution the chlorides might dissociate to a situation where there is just Cu II Cl 2 present with and without coordinated L1.…”

Ionogels Based on Poly(methyl methacrylate) and Metal-Containing Ionic Liquids: Correlation between Structure and Mechanical and Electrical Properties

“…It is also known that the tetrahalido ion, [CoCl 4 ] 2− shows a magnetic moment of 4.56 BM which assumes the value of 4.47 BM for [Bmim] 2 [CoCl 4 ] [ 69 ]. These results show that there is no strong evidence of a metal-metal interaction, similar to data by Strauch et al [ 70 ] who observed very weak metal-metal interactions in similar compounds. Table 2 summarizes the thermal properties and magnetic moments of [Bmim] 2 [CuCl 4 ], [Bmim] 2 [CoCl 4 ] and [Bmim] 2 [MnCl 4 ].…”

Catalytic catechol oxidation by copper complexes: development of a structure–activity relationship

“…S9 †). [32][33][34] As mentioned before, an abrupt increase is observed in the absorption at 400 nm at the start of the reaction. This 'jump' is likely caused by a change in absorption spectrum when the chloride ions dissociate from the copper center.…”