Low-Melting Manganese(II)-Based Ionic Liquids: Syntheses, Structures, Properties and Influence of Trace Impurities

Abstract

The synthesis of more than 10 new magnetic ionic liquids with [MnX4]2− anions, X = Cl, NCS, NCO, is presented. Detailed structural information through single-crystal X-ray diffraction is given for (DMDIm)[Mn(NCS)4], (BnEt3N)2[Mn(NCS)4], and {(Ph3P)2N}2[Mn(NCO4)]·0.6H2O, respectively. All compounds consist of discrete anions and cations with tetrahedrally coordinated Mn(II) atoms. They show paramagnetic behavior as expected for spin-only systems. Melting points are found for several systems below 100 °C classifying them as ionic liquids. Thermal properties are investigated using differential scanning calorimetry (DSC) measurements. The physicochemical properties of density, dynamic viscosity, electrolytic conductivity, and surface tension were measured temperature-dependent of selected samples. These properties are discussed in comparison to similar Co containing systems. An increasing amount of bromide impurity is found to affect the surface tension only up to 3.3%.

An overview of magnetic ionic liquids: From synthetic strategies to applications in microextraction techniques

“…2-] and [BMIM+] 2 [Mn(NCS) 4 2-] have been evaluated by applying NMR techniques and Langevin equation [51]. In this case, magnetic moments ranging from 5.9 to 6.0 μB at 25 • C were obtained for both compounds.…”

1-Benzyl-3-methylimidazolium bromide

“…These properties include, for instance, large liquid ranges, broad electrochemical windows as well as low vapor pressures (Hallett & Welton, 2011;Welton, 1999). The title compound, which is a useful starting material in our ongoing efforts to investigate metal-containing ionic liquids (Peppel et al, 2010;Peppel et al, 2017;Peppel et al, 2019) was obtained as single crystals over a period of several weeks directly from its pure, highly viscous and supercooled liquid. 1-Benzyl-3-methylimidazolium bromide expands the range of known single-crystal X-ray structures of ionic liquids of the general formula (BenzMIm)X (X = Cl, PF 6 (Ji et al, 2010;Hillesheim & Scipione, 2014) with a third example (X = Br).…”

Poly[1-ethyl-3-methylimidazolium [tri-μ-isothiocyanato-manganate(II)]]

“…Our ongoing efforts to investigate such low-melting metal-containing ionic liquids were first focused on compounds containing a cobalt ion (Kozlova et al, 2009Peppel et al, 2010). Later, Mn containing systems were included (Peppel et al, 2019).…”

“…The title compound, (EMIm)[Mn(NCS) 3 ], was obtained as light-green single crystals directly from a charge of pure, liquid (EMIm) 2 [Mn(NCS) 4 ] over a time period of several months. (EMIm) 2 [Mn(NCS) 4 ] was prepared via a salt metathesis reaction from 2.05 mmol of (EMIm)Br (Nishida et al, 2003) and 1.00 mmol of K 2 [Mn(NCS) 4 ] as a light-green liquid in moderate yield (>70%) (Peppel et al, 2019). Elemental analysis for C 16 H 22 MnN 8 S 4 % (calc.…”