Pairwise selective formation of aromatic stacks in a coordination cage

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Achieving asymmetric alignment of electron-donating (D) and electron-accepting (A) aromatic molecules in self-assembled stacks is a significant challenge.
• Typically, self-assembled aromatic structures result in alternating D-A-D-A arrangements, limiting precise control over molecular orientation.

Purpose of the Study:

• To demonstrate a novel strategy for creating quantitatively asymmetric aromatic stacking sequences.
• To investigate the dynamic behavior and controlling factors of guest molecules within a confined supramolecular environment.

Main Methods:

• Utilizing an electron-deficient aromatic 'box' as a host for guest molecules.
• Employing specific electron-donating (D) and electron-accepting (A) guest pairs.
• Characterizing the resulting stacking arrangement and guest dynamics using spectroscopic and computational methods.

Main Results:

• An asymmetric quadruple stacking sequence of A-D-A-A was quantitatively achieved by confining D-A guest pairs within the electron-deficient aromatic box.
• The inner D-A guest pair exhibited rapid positional swapping, forming a dynamic aromatic array.
• The rate of guest motion was found to be significantly dependent on the properties of the donor aromatics.

Conclusions:

• This work presents a successful method for controlling asymmetric aromatic stacking, overcoming the typical alternating D-A-D-A pattern.
• The dynamic nature of the guest molecules within the host box offers new possibilities for designing responsive and tunable supramolecular materials.
• The findings highlight the crucial role of donor aromatic properties in dictating guest mobility within confined supramolecular architectures.