Oxidation state variation in bis-calix[4]arene supported decametallic Mn clusters

Area of Science:

• Inorganic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Calixarene ligands are versatile macrocycles used in constructing complex metal-organic frameworks.
• Manganese-based clusters are of interest for their diverse magnetic properties and potential applications.
• Mixed-valent metal clusters offer tunable electronic and magnetic behaviors.

Purpose of the Study:

• To synthesize and characterize a novel mixed-valent decametallic manganese cluster.
• To investigate the structural and magnetic properties of the new cluster.
• To compare the magnetic behavior with a related manganese cluster having different oxidation states.

Main Methods:

• Synthesis of the decametallic cluster using MnCl2·4H2O, H8L (2,2'-bis-p-tBu-calix[4]arene), and NEt3 in a dmf/MeOH solvent mixture.
• Single-crystal X-ray diffraction for detailed structural elucidation.
• Density Functional Theory (DFT) calculations to analyze magnetic exchange interactions.

Main Results:

• Formation of a decametallic cluster [MnII6MnIII4(L)2(μ3-OH)4(μ-OH)4(MeOH)4(dmf)4(MeCN)2]·MeCN (3) with a mixed-valent MnII6MnIII4 core.
• The structure features a [MnIII4MnII6] metallic skeleton composed of three vertex-sharing [MnIII2MnII2] butterflies.
• DFT calculations show that replacing MnIII with MnII in a related cluster (4) significantly alters antiferromagnetic and ferromagnetic exchange interactions, reducing spin frustration.

Conclusions:

• The study successfully synthesized and characterized a unique decametallic manganese cluster stabilized by bis-calix[4]arene ligands.
• The mixed-valent nature and specific arrangement of manganese ions lead to distinct magnetic properties.
• The findings highlight the influence of oxidation state on magnetic exchange pathways and spin frustration in polynuclear manganese complexes.