Oximato-derived metal complexes with triangular and linear magnetic subunits: Synthesis, structure, and magnetism

ABSTRACT

Three oximato-based oligomeric metal complexes, {[Cu₃(H₂O)(µ₃-OH)(mpko)₃(NO₃)]·3H₂O·NO₃} (1), {[Cu₆(μ₃-OH)₂(mpko)₆(Br)₄]·8H₂O} (2), and {[Fe₃(mpko)₆]·ClO₄·2.5CH₃CN} (3) (mpkoH = 1-(pyrazin-2-yl)ethanone oxime), were synthesized by varying different spin carriers, and structurally and magnetically characterized. Structural determinations reveal that 1 is a discrete triangular {Cu₃(μ₃-OH)}⁵⁺ molecule with two adjacent metal ions further bridged by chelating-bridging mpko⁻ ligands. Complex 2 features a centrosymmetric hexanuclear entity with two triangular {Cu₃(μ₃-OH)}⁵⁺ subunits extended by a pair of bridging μ-Br⁻ anions. By contrast, 3 exhibits an approximately linear trinuclear entity with central Fe^III ion connected with two external Fe^II ions by six crystallographically unique mpko⁻ ligands. Strong antiferromagnetic interactions with the coupling constant up to 223(1) cm⁻¹ are observed in the triangular subunits of 1 and 2. In 3, the central Fe^III ion with S = 5/2 is almost magnetically isolated with the terminal Fe^II ions with S = 0.

KEYWORDS:

• Pyrazinyloximate
• oligomeric complex
• crystal structure
• magnetism

Supplementary material

Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Centre, 12 Union Road, Cambridge CB21EZ, England. Copies of the data can be obtained free of charge on quoting the depository numbers CCDC 1021005–1021007 (for 1–3) (Fax: [phone]; E-mail: [email protected], http://www.ccdc.cam.ac.uk).

Funding

This work was financially supported by the National Natural Science Foundation of China (21173157 and 21303121) and the Program for Innovative Research Team in University of Tianjin (TD12−5038), which are gratefully acknowledged.