ИСТИНА

Due to different unique properties (low melting point, ionic structure, negligible vapor pressure, electrochemical and thermal stability, ionic conductivity etc.) ionic liquids (IL) have not only fundamental scientific interest, but the applied significance as well. Highly perspective feature is to design desirable properties by functional group embedding to cation and anion selection [1]. The present work deals with ionic liquids with diethanolammonium cation and metal-halogenide anions. Diethanolammonium (HOCH2CH2)2NH2+ has acidic protons (OH and NH2+ groups) and IL could have protonic conductivity potentially. The metal-based anion in IL is often responsible for magnetic, catalytic and electrochemical properties [2]. The syntheses of these ILs consisted of two stages: on the first stage the salt of diethanolamine (DEA) and hydrochloric acid was produced; the second stage included reaction between the salt made on 1st stage (DEAHCl) and corresponding water free metal chloride (FeCl3, CoCl2, MnCl2). The resulting compounds were drying in desiccator over P4O10. All of them were characterized by single crystal XRD, thermal analyses (DTA-TG, DSC), IR spectroscopy. Thermal properties are shown in Table 1. Table 1. Thermal properties of ILs. Compound Melting point, °C Decomposition Temperature, °C DEAHFeCl4 31.0 128-486 (DEAH)2CoCl4 48.7 210-525 DEAHMnCl3 162.4 269-272 Crystal structures of ILs DEAHFeCl4 and (DEAH)2CoCl4 at room temperature are composed of cations DEAH and anions MCl4, whereas in DEAHMnCl3 cation DEAH is connected to manganese atom by coordination bond through oxygen atom of OH group (Fig. 1). This fact causes melting point to increase (see Table 1). Hydrogen bonding systems in all three structures are different. In DEAHFeCl4 cations DEAH are combined by O–H···O hydrogen bonds to tetramers (Fig. 2) which are connected to corrugated layers. Protonic conductivity could be found along these layers. Layers of cations are joined by anions to 2D structure, therefore DEAHFeCl4 is layer structure. In (DEAH)2CoCl4 cations are linked to chains through N–H···O hydrogen bonds, skew cation chains are connected with anions to 3D structure. Finally there are disordering hydrogen system in DEAHMnCl3 structure (Fig. 3). Blue dashed lines are the first hydrogen bonding system occurring simultaneously O1–H11···O21, O21–H22···O22, O22–H21···Cl3 and O1–H12···Cl3. The second hydrogen bonding system is shown by magenta dashed lines in Fig.3. This system is symmetry equivalent to blue one and both systems arrange in crystal statistically. Manganese atom has 5 chlorine atoms in closed environment and one oxygen atom from cation DEAH, whereas 4 chlorine atoms are bridge. Thus the chain from Mn and Cl is formed with adjoined cations DEAH. These chains are connected to 3D structure through hydrogen bonding. In conclusion, the structure of ionic liquid is dramatically depended on the kind of metal in metal-chloride anion, iron produces low melting ionic liquid with layered structure and disordering hydrogen bond system, cobalt gives moderate melting ionic liquid with 3D structure and chain-like hydrogen bonding system, manganese yields 3D structure with disordering hydrogen bonding system, extended (MnCl3)n-chains with coordinated DEAH and, as consequence, high melting point. This work was supported in part by M.V. Lomonosov Moscow State University Program of Development. References [1] Aslanov L.A., Zakharov M.A., Abramycheva N.L. Ionic Liquids in row of solvents. M.: MSU Publishing. 2005. 272 p. [2] Zazybin A., Rafikova Kh., Yu V., Zolotareva D., Dembitsky V. M. and Sasaki T. Russ. Chem. Rev., 2017, 86, 1254.