Pseudorotaxane formation affected by stereo-electronic effects. A theoretical and experimental study

Area of Science:

• Supramolecular Chemistry
• Computational Chemistry

Background:

• Pseudorotaxanes are mechanically interlocked molecules with potential applications in molecular machines.
• Understanding the factors governing their formation is crucial for designing novel supramolecular systems.

Purpose of the Study:

• To investigate the influence of methyl substituent positions on pyridine axles in pseudorotaxane complex formation.
• To evaluate the interplay of electronic and steric effects in these systems.

Main Methods:

• Synthesis of pyridine-based pseudorotaxane complexes with varying methyl substituent patterns.
• Molecular dynamics (MD) and quantum mechanical (QM) calculations.
• Molecular electrostatic potential (MEP) mapping.
• Nuclear Magnetic Resonance (NMR) spectroscopy for experimental validation.

Main Results:

• Methyl substituent positions significantly impact the stereo-electronic properties and behavior of pseudorotaxane complexes.
• Both electronic and steric factors are critical for the feasibility of complex formation.
• Computational simulations accurately predict the ease or difficulty of complex formation.
• Visualization of external complex formation in rotaxanes was achieved using bolaform linkers.

Conclusions:

• The combination of MD, QM, and MEP is a powerful approach for predicting pseudorotaxane formation.
• The study provides insights into controlling the self-assembly of rotaxane systems.
• Understanding these factors enables the rational design of new supramolecular architectures.