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, [Cu 2 (phen) 4 (GeW 12 O 40 )] (1) and [Ni 2 (bpy) 4 (H 2 O) 2 (Ge-W 12 O 40 )]·2H 2 O (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.

Hydrothermal synthesis and crystal structures of a novel Keggin-type polyoxometalate based on 1,10-phenanthroline

“…The weight loss in the range of 478-690 °C is attributed to the decomposition of the two 1,10-phenanthroline ligands (calc. 26.7%; found 27.1%) [41].…”