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Supramolecular recognition: protonmotive-driven switches or motors?
James D Crowley1, Andrew J Goshe, Ian M Steele
1Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|April 14, 2004
Summary
A dicationic receptor binds platinum(II) guests. Protonation of the guest by acid causes it to detach, acting like a molecular switch driven by electrostatic repulsion, similar to a molecular motor.
Area of Science:
- Supramolecular Chemistry
- Chemical Sensing
- Molecular Machines
Background:
- Dicationic molecular receptors can form stable complexes with planar, neutral platinum(II) guests.
- The interaction between host and guest can be modulated by chemical stimuli.
Purpose of the Study:
- To investigate the formation and dissociation of host-guest complexes using a dicationic receptor and a modified platinum(II) guest.
- To explore the potential of this system as a molecular switch or motor.
Main Methods:
- Synthesis of a dicationic receptor with terpyridyl-Pd-Cl units.
- Complexation studies with planar, neutral platinum(II) complexes.
- Protonation and deprotonation experiments using trifluoroacetic acid and base in acetonitrile.
Main Results:
- Stable 1:1 host-guest complexes were formed between the dicationic receptor and platinum(II) guests.
- Protonation of a pyridine-functionalized guest by trifluoroacetic acid led to its dissociation from the receptor.
- Addition of base restored the host-guest complex, demonstrating reversible binding.
Conclusions:
- The observed guest displacement is attributed to electrostatic repulsion between the dicationic receptor and the protonated guest.
- The system functions as a molecular switch, controlled by protonation/deprotonation, mimicking a stroke in molecular motors.
- This work provides insights into the design of responsive supramolecular systems and molecular machines.