Ternary π-π Stacking Complexes by Allosteric Regulation in Multilayer Nanographenes

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Constructing multi-component π-π stacking supramolecular complexes is difficult due to weak, directionless dispersion forces.
• Existing methods struggle to control the assembly of more than two distinct components in such systems.

Purpose of the Study:

• To report the formation of ternary complexes involving a nanographene tetraimide, phthalocyanine, and polyaromatic hydrocarbons.
• To demonstrate the use of allosteric regulation for constructing complex supramolecular architectures.
• To investigate the stability and formation of these ternary complexes in solution and the crystalline state.

Main Methods:

• Synthesis of a ditopic nanographene tetraimide (1).
• Complexation studies involving (1), α-substituted phthalocyanine (Pc), and polyaromatic hydrocarbons (PAHs).
• Characterization using 1H NMR titration and cocrystallization techniques.

Main Results:

• Allosteric regulation was achieved: binding of Pc induced conformational changes in (1), inhibiting further Pc binding but enabling PAH binding.
• Stable ternary complexes ([Pc·1·PAH]) were formed in solution, as evidenced by NMR titration.
• Ternary cocrystals were selectively generated from a 1:1:1 mixture of the components in solution.

Conclusions:

• Large π-conjugated nanographenes with allosteric sites facilitate the construction of ternary complexes.
• This approach allows for the creation of multilayered supramolecular structures in both solution and solid states.
• The study overcomes limitations of weak π-π interactions for complex assembly.