Allosteric deprogramming of a trinuclear heterometallic helicate

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Development of multidentate ligands is crucial for constructing complex metallosupramolecular architectures.
• Crown ether moieties within ligands offer potential for ion recognition and coordination.
• Heterometallic complexes with specific nuclearities are of interest for their unique properties.

Purpose of the Study:

• To synthesize and characterize novel ditopic ligands (L1 and L2) incorporating N-donor and crown ether units.
• To investigate the self-assembly of these ligands with Cu(I) and Zn(II) ions to form heterometallic double helicates.
• To explore the reactivity of the formed complexes with barium ions (Ba2+).

Main Methods:

• Synthesis of multidentate ditopic ligands L1 and L2.
• Formation and characterization of heterometallic double helicates using techniques such as 1H NMR, ESI-MS, and single crystal X-ray crystallography.
• Reactions of the synthesized complexes with Ba2+ ions.

Main Results:

• Ligand L1 formed a trinuclear heterometallic double helicate with Cu(I) and Zn(II) ions: [Zn2Cu(L1)2](5+).
• Ligand L2 formed a tetranuclear heterometallic double helicate with Cu(I) and Zn(II) ions: [Zn2Cu2(L2)2](6+).
• Reaction of [Zn2Cu2(L2)2](6+) with Ba2+ yielded a stable barium-coordinated species [Zn2Cu2(L2)2Ba2](10+), while [Zn2Cu(L1)2](5+) reacted with Ba2+ to deprogram and form a mixture of species.

Conclusions:

• The designed ligands L1 and L2 successfully form distinct heterometallic double helicates with different nuclearities.
• The crown ether units in L2 facilitate coordination with Ba2+, leading to a stable complex.
• The structural integrity of the helicate formed by L1 is compromised upon reaction with Ba2+, indicating differential stability and reactivity.