Synthesis, Structure, and Physico‐optical Properties of Manganate(II)‐Based Ionic Liquids

Abstract

Several ionic liquids (ILs) based on complex manganate(II) anions with chloro, bromo, and bis(trifluoromethanesulfonyl)amido (Tf(2)N) ligands have been synthesized. As counterions, n-alkyl-methylimidazolium (C(n)mim) cations of different chain length (alkyl=ethyl (C(2)), propyl (C(3)), butyl (C(4)), hexyl (C(6))) were chosen. Except for the 1-hexyl-3-methylimidazolium ILs, all of the prepared compounds could be obtained in a crystalline state at room temperature. However, each of the compounds displayed a strong tendency to form a supercooled liquid. Generally, solidification via a glass transition took place below -40 degrees C. Consequently, all of these compounds can be regarded as ionic liquids. Depending on the local coordination environment of Mn(2+), green (tetrahedrally coordinated Mn(2+)) or red (octahedrally coordinated Mn(2+)) luminescence emission from the (4)T(G) level is observed. The local coordination of the luminescent Mn(2+) centre has been unequivocally established by UV/Vis as well as Raman and IR vibrational spectroscopies. Emission decay times measured at room temperature in the solid state (crystalline or powder) were generally a few ms, although, depending on the ligand, values of up to 25 ms were obtained. For the bromo compounds, the luminescence decay times proved to be almost independent of the physical state and the temperature. However, for the chloro- and bis(trifluoromethanesulfonyl)amido ILs, the emission decay times were found to be dependent on the temperature even in the solid state, indicating that the measured values are strongly influenced by nuclear motion and the vibration of the atoms. In the liquid state, the luminescence of tetrahedrally coordinated Mn(2+) could only be observed when the tetrachloromanganate ILs were diluted with the respective halide ILs. However, for [C(3)mim][Mn(Tf(2)N)(3)], in which Mn(2+) is in an octahedral coordination environment, a weak red emission from the pure compound was found even in the liquid state at elevated temperatures.

Computational insights into the molecular interaction and ion-pair structures of a novel zinc-functionalized ionic liquid, [Emim][Zn(TFSI)3]

“…Even the weakly coordinating triflimidate ligand such as [TFSI]ˉ has been shown to form metal chelates [43][44][45][46]. Crystal structures of Zn(TFSI) 2 [43] …”

Intense photo- and tribo-luminescence of three tetrahedral manganese(ii) dihalides with chelating bidentate phosphine oxide ligand

“…Green block crystals of 2 suitable for Xray analyses were directly obtained after opening the Teflon-55 lined stainless-steel autoclave, washed with diethyl ether and dried in air. Yield: 76% (based on POP) for 2 2. (DPEPO)] (3).The procedure was the same as that for 2 except that MnBr 2 ·2H 2 O was replaced by anhydrous MnI 2 (0.4 mmol, 0.124 g).…”

Magnetic ionic liquid assisted single‐drop microextraction of ascorbic acid before its voltammetric determination

“…. It has been demonstrated that the electronic transitions appeared at 300–800 nm can be attributed to the intraconfigurational transitions of Mn(II) ion . Two distinct groups of absorption bands observed in the ACTM spectrum in the region of 335–500 nm are assigned to the tetrahedral‐coordinated MnCl 4 2− anion and so confirm the synthesis of the MIL .…”