Ionic liquid, glass or crystalline solid? Structures and thermal behaviour of (C4mim)2CuCl3

Area of Science:

• Materials Science
• Solid-State Chemistry
• Ionic Liquids

Background:

• Ionic liquids are salts that are liquid at low temperatures.
• Copper-based ionic liquids are of interest for various applications.
• Understanding the structural and thermal properties of ionic liquids is crucial for their development.

Purpose of the Study:

• To synthesize and characterize a new ionic liquid, (C4mim)2CuCl3.
• To investigate the crystalline structures and phase transitions of this ionic liquid.
• To determine its thermal properties, including melting point and glass transition temperature.

Main Methods:

• Synthesis of (C4mim)2CuCl3 from copper(I) chloride and 1-butyl-3-methylimidazolium chloride.
• Crystallographic analysis to determine the crystal structures of different modifications.
• Thermoanalytical methods (e.g., differential scanning calorimetry) to study phase transitions and melting behavior.

Main Results:

• The ionic liquid (C4mim)2CuCl3 consists of C4mim(+) cations and triangular [CuCl3](2-) anions.
• Three distinct crystalline modifications were identified, with phase transitions occurring at 227 K and 203 K.
• The compound melts congruently at 320 K with an enthalpy of fusion of 25.7 kJ mol(-1) and exhibits a glass transition at 221 K.

Conclusions:

• The synthesized ionic liquid (C4mim)2CuCl3 displays complex solid-state behavior with multiple crystalline phases.
• The observed phase transitions and glass transition highlight the dynamic nature of this ionic liquid.
• The study provides fundamental insights into the structural and thermal properties of copper-containing ionic liquids.