Anion and pH dependent molecular motion by a halogen bonding [2]rotaxane

Area of Science:

• Supramolecular Chemistry
• Molecular Machines
• Chemical Sensing

Background:

• Rotaxanes are molecular machines with a ring threaded onto an axle.
• Bistable rotaxanes can exist in two distinct states.
• Halogen bonding is a non-covalent interaction crucial for molecular recognition.

Purpose of the Study:

• To design and synthesize a novel bistable [2]rotaxane.
• To investigate the stimuli-responsive behavior of the rotaxane.
• To develop a colorimetric sensor based on rotaxane conformational changes.

Main Methods:

• Synthesis of a [2]rotaxane featuring a benzimidazole-iodotriazole station and a naphthalimide station.
• Investigating macrocycle shuttling via protonation and chloride anion binding.
• Monitoring conformational changes using UV-Vis spectroscopy for color detection.

Main Results:

• The rotaxane exhibits bistability, with the macrocycle positioned on one of two stations.
• Macrocycle shuttling occurs selectively upon simultaneous protonation and chloride anion recognition.
• A distinct color change is observed, enabling naked-eye detection of the stimuli.

Conclusions:

• The developed [2]rotaxane functions as a switchable molecular machine.
• The system demonstrates a novel approach for stimuli-responsive molecular devices.
• This work paves the way for advanced chemical sensors with visual output.