Formation of [FeW₁₂O₄₀]⁵⁻ under hydrothermal conditions: syntheses, crystal structures, and characterization of [Fe(2,2′-bipy)₃]₂[HFeW₁₂O₄₀] · 5H₂O and (4,4′-H₂bipy)₆(Hpy)₂(H₃O)[FeW₁₂O₄₀]₃ · 11H₂O

Abstract

Two supramolecular compounds based on tungstoferrate [FeW₁₂O₄₀]⁵⁻, [Fe^II(2,2′-bipy)₃]₂[HFeW₁₂O₄₀] · 5H₂O (1), and [Hpy]₂[4,4′-H₂bipy]₆(H₃O)[FeW₁₂O₄₀]₃ · 11H₂O (2) (py = pyridine, bipy = bipyridine) were synthesized hydrothermally and characterized structurally. The hydrogen bonds between polyoxoanions and water and the edge-to-face π–π interaction between [Fe^II(2,2′-bipy)₃]²⁺ with a shortest C–C distance of 3.513 Å are the main forces to construct the 3-D architecture of 1. In 2, a 3-D supramolecular architecture is assembled by the tungstoferrate anions, protonated 4,4′-bipy cations, and water through hydrogen bonding. The variable-temperature magnetic susceptibilities indicate that 1 is paramagnetic with μ _eff corresponding to one Fe(III) with spin-only contribution, showing that Fe in the coordination cations has a +II oxidation number and low spin state.

Keywords:

• Tungstoferrate
• Hydrothermal synthesis
• Hydrogen bond
• Iron
• Crystal structure

Acknowledgment

This work was supported by Analysis and Testing Foundation of the Northeast Normal University.