Tetranuclear silver(I) clusters showing high ionic conductivity in a bicontinuous cubic mesophase

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Coordination Chemistry

Background:

• Metallomesogens are coordination compounds that exhibit liquid crystalline properties.
• Silver-based metallomesogens are of interest due to silver's unique electronic and coordination properties.
• Triazole ligands offer versatile coordination modes and can influence mesophase behavior.

Purpose of the Study:

• To synthesize and characterize novel tetranuclear silver triazole metallomesogens.
• To investigate the liquid crystalline phase behavior of these compounds as a function of alkyl chain length.
• To evaluate the ionic conductivity of the observed mesophases.

Main Methods:

• Synthesis of tetranuclear silver complexes with 4-alkyl-1,2,4-triazole ligands.
• Thermal analysis (Differential Scanning Calorimetry, Thermogravimetric Analysis) to determine phase transitions.
• Polarized Optical Microscopy to identify liquid crystalline phases.
• X-ray diffraction to characterize cubic phases.
• Electrochemical impedance spectroscopy to measure ionic conductivity.

Main Results:

• Successful synthesis of [Ag4(L(4)-C(n))6][BF4]4 (n = 12, 14, 16, 18).
• Observed phase transition sequence: Cr → SmC → Cub → SmA → isotropic liquid.
• Identification of micellar cubic phases for shorter chains (n=12, 14) and bicontinuous cubic phases for longer chains (n=16, 18).
• Superior ionic conductivity in the bicontinuous cubic mesophase of [Ag4(L4-C16)6][BF4]4 due to 3D ion-transport channels.
• Dramatic enhancement of ionic conduction upon doping with AgBF4.

Conclusions:

• Tetranuclear silver triazole metallomesogens display rich liquid crystalline behavior.
• Alkyl chain length dictates the type of cubic mesophase formed.
• The bicontinuous cubic phase exhibits promising ionic conductivity, potentially tunable by doping.
• These materials could be relevant for ion conduction applications.