α-Keggin tungstogermanate-supported transition metal complexes: hydrothermal synthesis, characterization, and magnetism of Cu₂(phen)₄(GeW₁₂O₄₀) and [Ni₂(bpy)₄(H₂O)₂(GeW₁₂O₄₀)]⋅2H₂O

Abstract

Two new α-Keggin polyoxometalates, [Cu₂(phen)₄(GeW₁₂O₄₀)] (1) and [Ni₂(bpy)₄(H₂O)₂(GeW₁₂O₄₀)]·2H₂O (2) (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine), have been hydrothermally synthesized and characterized by elemental analysis, IR, TG, single-crystal X-ray diffraction, and magnetic properties. Compound 1 crystallizes in the monoclinic system, space group P2(1)/c, and 1 is assembled into two-dimensional (2-D) layers parallel to (1 0 1) based on the adjacent phen π···π stacking interactions (3.788(8) Å). Variable temperature magnetic measurements show ferromagnetic behavior from 300 to 2 K. Compound 2 crystallizes in the triclinic system, space group P-1, and 2 is assembled into 2-D layers parallel to (1 0 1) based on the adjacent bpy π···π stacking interactions (3.07 Å). Variable temperature magnetic measurements show a weak ferromagnetic behavior from 300 to 26 K followed by antiferromagnetic behavior below 26 K.

Keywords:

• Transition metal complexes
• α-Keggin polyoxometalates
• Tungstogermanates
• Crystal structure
• Magnetic property

Funding

This project was supported by the National Natural Science Foundation of China [grant number 51343003]; the Zhejiang Provincial Science and Technology Project of China [grant number 2011C31041]; the Scientific Research Fund of Zhejiang Provincial Education Department [grant number Y201224707], [grant number Y201120940].