1,4-Bis[2-(4-ferrocenylphenyl)ethynyl]anthraquinone from synchrotron X-ray powder diffraction

Area of Science:

• Coordination Chemistry
• Materials Science
• Crystallography

Background:

• The synthesis of novel porous materials is crucial for applications in gas storage, separation, and catalysis.
• Anthraquinone and ferrocene derivatives are known for their unique electronic and structural properties.

Purpose of the Study:

• To synthesize a new solvent-incorporating porous material using ferrocenylphenyl and anthraquinone units.
• To investigate the crystal structure and phase transition behavior of the synthesized compound.

Main Methods:

• Synthesis of 1,4-(FcPh)2Aq (ferrocenylphenyl-anthraquinone).
• Thermodynamic analysis to identify phase transitions.
• Synchrotron X-ray powder diffraction at variable temperatures (90 K, 300 K, 500 K).
• Direct-space structure solution using a genetic algorithm.
• Maximum entropy method for charge density calculation and model improvement.
• Multistage Rietveld refinements for final structural models.

Main Results:

• A phase transition was observed at approximately 430 K.
• The crystal structure, determined at 90 K, 300 K, and 500 K, showed subtle differences between phases.
• Planar anthraquinone fragments formed one-dimensional columns with alternating orientations.
• Ferrocenylphenyl arms occupied the space between stacks, preventing void formation.
• C-H...π interactions were identified as key to crystal packing and stabilization.

Conclusions:

• The synthesized ferrocenylphenyl-anthraquinone compound does not form a porous material with large void spaces as initially intended.
• The crystal packing is dominated by the arrangement of anthraquinone columns and the filling role of ferrocenylphenyl arms.
• C-H...π interactions play a significant role in stabilizing the crystal structure.