Water-Mediated Reversible Control of Three-State Double-Stranded Titanium(IV) Helicates

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Materials Science

Background:

• Stimuli-responsive reversible structural transformations are crucial in biological systems.
• Controlling the assembly and disassembly of complex molecular architectures remains a significant challenge.

Purpose of the Study:

• To report a unique water-mediated reversible transformation among three discrete double-stranded dinuclear titanium(IV) helicates.
• To investigate the role of hydration/dehydration and titanium-phenoxide bond dynamics in structural interconversion.
• To demonstrate controllable generation of achiral meso- and chiral rac-helicates.

Main Methods:

• Synthesis of bis(μ-hydroxo)-bridged titanium(IV) meso-helicate.
• Controlled hydration/dehydration experiments in various solvent conditions (CD3CN, aqueous CD3CN).
• Investigation of acid catalysis and the effect of cryptand[2.2.1] on reaction rates and pathways.
• Structural characterization through spectroscopic methods (implied).

Main Results:

• Demonstrated reversible transformation between bis(μ-hydroxo)-bridged meso-helicate and mono(μ-oxo)-bridged rac-helicate via hydration/dehydration and Ti-OPh bond dynamics.
• Showcased acid catalysis accelerating the transformations at lower temperatures.
• Reported a meso-to-meso helicate transformation in anhydrous conditions, influenced by Na+ ion removal.
• Successfully generated three distinct titanium(IV) helicates in a controllable manner by adjusting water content.

Conclusions:

• Water content is a key external stimulus for controlling reversible structural transformations in titanium(IV) helicates.
• The dynamic cleavage and re-formation of Ti-OPh bonds, mediated by water, are central to these transformations.
• This work provides a versatile platform for the controllable synthesis of complex chiral and achiral supramolecular structures.