Crystal structures of

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Crystal Engineering

Background:

• Polyammonium macrocycles are versatile ligands in coordination chemistry.
• Hexacyanocobaltate complexes exhibit interesting structural and binding properties.
• Understanding host-guest interactions in supramolecular systems is crucial.

Purpose of the Study:

• To determine the crystal structures of three supercomplexes involving protonated polyammonium macrocycles and potassium hexacyanocobaltate.
• To investigate the binding competition between potassium ions and hexacyanocobaltate anions with macrocycles.
• To elucidate the role of macrocycle cavity size and interaction types in complex formation.

Main Methods:

• Single-crystal X-ray diffraction was used to determine the crystal structures.
• Analysis of intermolecular interactions, including electrostatic and hydrogen bonding, was performed.
• Comparative study of complexes with different macrocycle sizes.

Main Results:

• The crystal structures of potassium dihydrogen hexacyanocobaltate with [18]aneN(6), [16]aneN(4), and [12]aneN(4) macrocycles were elucidated.
• Hexacyanocobaltate binding to protonated macrocycles dominated over potassium ion binding.
• Hexacyanocobaltate binding was independent of macrocycle cavity size, while potassium ion binding was size-selective.
• Different network structures (2D lamella, 3D zeolite-type) were observed, driven by electrostatic and hydrogen-bonding interactions.

Conclusions:

• The binding affinity of hexacyanocobaltate to protonated polyammonium macrocycles is robust and size-independent.
• Potassium ion binding is governed by size-matching selectivity.
• The observed crystal structures highlight the intricate interplay of electrostatic and hydrogen-bonding forces in supramolecular assembly.
• These findings contribute to the understanding of complex formation in solution and solid states.