Hexanuclear Cu₃O-3Cu triazole-based units as novel core motifs for high nuclearity copper(ii) frameworks

Area of Science:

• Coordination Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• The synthesis of polynuclear metal complexes is crucial for developing advanced functional materials.
• Asymmetric 3,5-disubstituted 1,2,4-triazole ligands offer versatile coordination modes for constructing complex architectures.
• Copper(II) perchlorate is a common precursor for synthesizing copper-based coordination compounds.

Purpose of the Study:

• To synthesize and characterize novel copper(II) coordination compounds using a specific 1,2,4-triazole ligand.
• To investigate the structural diversity, including hexanuclear, dodecanuclear, and tetradecanuclear assemblies.
• To explore the magnetic properties of the resulting copper clusters.

Main Methods:

• Reaction of the 1,2,4-triazole ligand H2V (5-amino-3-picolinamido-1,2,4-triazole) with excess copper(II) perchlorate.
• Single-crystal X-ray diffraction for structural determination of the hexanuclear, dodecanuclear, and tetradecanuclear complexes.
• Magnetic susceptibility measurements and analysis to determine magnetic coupling parameters.

Main Results:

• Formation of a novel hexanuclear {Cu6(μ3-O/H)(HV/V)3} fragment acting as a building block.
• Synthesis of three distinct structures: a hexanuclear complex [Cu6(μ3-O)(HV)3(ClO4)7(H2O)9]·8H2O, a dodecanuclear complex [Cu12(μ3-O)2(V)6(ClO4)5(H2O)18](ClO4)3·6H2O, and a tetradecanuclear 1D-polymer {[Cu14(μ3-OH)2(V)6(HV)(ClO4)11(H2O)20](ClO4)2·14H2O}.
• The hexanuclear cluster exhibits significant intra-triangle antiferromagnetic coupling (J = -247.0(1) cm⁻¹) and weaker coupling between central and external copper ions (j = -5.15(2) cm⁻¹).

Conclusions:

• The 1,2,4-triazole ligand facilitates the construction of diverse and complex copper(II) coordination architectures.
• The study demonstrates the formation of unique hexanuclear, dodecanuclear, and 1D-polymeric structures.
• The magnetic properties of the hexanuclear cluster provide insights into the electronic interactions within the copper core.