Trifluoromethyl-substituted tetrathiafulvalenes

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Tetrathiafulvalenes (TTFs) are versatile organic semiconductors.
• Electron-withdrawing groups (EWGs) significantly modulate TTF electronic properties.
• Trifluoromethyl (CF3) groups offer unique electronic and steric effects.

Purpose of the Study:

• Synthesize novel TTFs functionalized with trifluoromethyl (CF3) EWGs.
• Investigate the impact of CF3 groups on TTF core properties.
• Explore the potential of these TTFs in charge transfer complexes and radical cation salts.

Main Methods:

• Phosphite coupling for TTF synthesis.
• Structural analysis via X-ray crystallography.
• Electrochemical and spectrochemical characterization.
• Density Functional Theory (DFT) calculations.

Main Results:

• Successfully synthesized TTFs with one or two CF3 EWGs.
• Electrochemical data correlated oxidation potentials with Hammett parameters, showing limited mesomeric effects.
• Crystal structures revealed minimal modification of dithiole ring deformation by CF3 groups.
• DFT calculations indicated altered electronic transitions in CF3-substituted TTFs.
• Isolated and characterized a neutral charge transfer complex (EDT-TTF-CF3)2(TCNQ) and a radical cation salt (EDT-TTF-CF3)(FeCl4).

Conclusions:

• CF3 groups act as effective EWGs influencing TTF redox potentials.
• The electronic and structural effects of CF3 are distinct from ester or nitrile groups.
• CF3-substituted TTFs can form stable charge transfer complexes and radical cation salts.
• These materials exhibit interesting solid-state properties, including paired radical cations in a singlet state.