Organometallic Ionic Plastic Crystals Incorporating Cationic Half-Sandwich Complexes

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Ionic plastic crystals (IPCs) are known for high ionic conductivity due to spherical ions.
• Incorporating low-symmetry organometallic complexes into IPCs is synthetically challenging.
• Existing IPCs are predominantly organic onium salts.

Purpose of the Study:

• To synthesize and characterize novel ionic plastic crystals (IPCs) based on organometallic half-sandwich complexes.
• To investigate the influence of different anions on the phase behavior, crystal structure, and solid-state dynamics of these new IPCs.
• To explore the potential of these materials for applications requiring high ionic conductivity.

Main Methods:

• Synthesis of five novel salts of [Ru(Cp)(tmeda)(CO)]X with varying anions.
• Analysis of phase transitions using temperature-dependent studies.
• Determination of crystal structures and coordination numbers in different solid-state phases.
• Investigation of molecular motion in the solid-state.

Main Results:

• Three salts with CPFSA, B(CN)4-, and FSA- anions transitioned to a CsCl-type IPC phase between 327-364 K.
• Smaller anions increased the transition temperature to the IPC phase.
• Salts with CF3BF3- and PF6- anions formed rotator phases instead of IPC phases, exhibiting a coordination number of six.
• Coordination number remained eight in the IPC and low-temperature phases for the studied salts.

Conclusions:

• Novel organometallic IPCs were successfully synthesized and characterized.
• Anion size significantly impacts the formation of the IPC phase and transition temperatures.
• These findings expand the scope of materials for ionic plastic crystals and solid-state ionic applications.