Optically active derivatives of terephthalic acid: four crystal structures from two powder patterns

Area of Science:

• Materials Science
• Crystallography
• Organic Chemistry

Background:

• Metal-organic frameworks (MOFs) are versatile nanoporous crystalline materials.
• MOFs are platforms for developing functional hybrid materials, including asymmetric catalysts.
• Chiral linkers are crucial for constructing enantioselective MOFs.

Purpose of the Study:

• To synthesize novel chiral linkers for MOF-based asymmetric catalysts.
• To explore the potential of terephthalic acid derivatives as chiral linkers.
• To determine the crystal structures of synthesized compounds and their hydrates/polymorphs.

Main Methods:

• Synthesis of two terephthalic acid derivatives: 2-{[1-(1-tert-butoxycarbonyl)-L-prolyl]amino}terephthalic acid (1) and 2-(L-prolylamino)terephthalic acid (2).
• Powder X-ray diffraction measurements at synchrotron station ID22 (ESRF).
• Crystal structure determination of four new crystalline phases and validation using DFT-d optimizations.

Main Results:

• Four new crystal structures were determined: two crystallohydrates of (1) (1a and 1b) and two polymorphs of (2) (2a and 2b).
• The determined space groups were C2221 and P2221 for hydrates of (1), and C2221 and P212121 for polymorphs of (2).
• The synthesized compounds demonstrated potential as chiral linkers for enantioselective MOFs.

Conclusions:

• The study successfully synthesized and characterized novel chiral linkers for MOF applications.
• The determined crystal structures provide a foundation for designing enantioselective MOFs.
• These findings contribute to the development of advanced MOF-based asymmetric catalysts.