Aromatic Interactions Select for Homodimeric Assembly in a Quadruply Hydrogen-Bonded DADA 1,2-Azaphosphinine Dimer

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Azaphosphinine heterocycles are versatile scaffolds in supramolecular chemistry.
• Hydrogen bonding plays a crucial role in self-assembly and molecular recognition.
• Chiral molecules offer unique properties for advanced materials and asymmetric synthesis.

Purpose of the Study:

• To design and synthesize novel chiral azaphosphinine derivatives with quadruple hydrogen bonding capabilities.
• To investigate the influence of substituents on homodimerization strength and orientation.
• To explore the formation of chiral homodimers and their potential in supramolecular chemistry.

Main Methods:

• Synthesis of eleven azaphosphinine derivatives with varying electron donor and acceptor groups.
• Spectroscopic analysis (NMR) to determine dimerization constants.
• X-ray crystallography to elucidate the solid-state structure and hydrogen bonding.
• Computational modeling (DFT) to understand electronic and geometric preferences.

Main Results:

• Azaphosphinine derivatives functionalized with N-acetamide groups formed chiral quadruple hydrogen bonding faces.
• Dimerization constants reached up to 209 M⁻¹ with electron-donating groups.
• X-ray crystallography revealed a preference for the DADA hydrogen bond orientation.
• First examples of R,R- and S,S-azaphosphinine homodimers were observed, explained by computational analysis.

Conclusions:

• The designed azaphosphinines exhibit strong homodimerization through quadruple hydrogen bonding.
• Substituent effects on hydrogen bond acceptors are more pronounced than on donors.
• The DADA orientation is favored due to pyridine aromaticity stabilization.
• These findings pave the way for integrating these systems into complex supramolecular architectures.