Topology modulation in Ni(II) helicates through SiF₆^2--directed self-assembly

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Crystal Engineering

Background:

• Self-assembly is a key process in constructing complex molecular architectures.
• Anion templating offers a powerful strategy for directing the formation of specific supramolecular structures.
• Bis(pyrazolyl)pyridine ligands are versatile building blocks in coordination chemistry.

Purpose of the Study:

• To investigate the templating effect of the hexafluorosilicate (SiF6^2-) anion on the self-assembly of nickel complexes.
• To synthesize and characterize novel heteroleptic triple-stranded helicates and tetranuclear architectures.
• To understand the role of guest symmetry and hydrogen bonding in dictating supramolecular assembly.

Main Methods:

• Coordination of nickel ions with bis(pyrazolyl)pyridine ligands (L1 and L2).
• Crystallization in the presence of the hexafluorosilicate (SiF6^2-) anion.
• X-ray crystallography for structural determination of the resulting supramolecular assemblies.

Main Results:

• Formation of a rare heteroleptic triple-stranded helicate: (SiF6@[Ni2(L1)(L2)2])^2+.
• Discovery of an unprecedented tetranuclear nickel architecture: ((SiF6)2@[Ni4(L1)6])^4+.
• Demonstration of directional F⋯H-N hydrogen bonds reinforcing guest symmetry and assembly topology.

Conclusions:

• The hexafluorosilicate (SiF6^2-) anion acts as a crucial template, directing the formation of unique nickel-based supramolecular structures.
• Guest symmetry plays a significant role in controlling the composition and topology of self-assembled coordination compounds.
• This study highlights the potential of anion templating and hydrogen bonding in designing intricate supramolecular architectures.