Layered Tungsten Oxide-Based Hybrid Materials Incorporating Transition Metal Ions

Abstract

Layered organic-inorganic hybrid materials based on tungsten oxide as the inorganic framework have been synthesised to include transition metal ions. The resulting materials have been characterised using a number of techniques. X-ray diffraction shows an interlayer expansion with increasing alkyl length. Infrared vibrational spectra of manganese tungstate compounds indicate the organic amine molecules are neutrally charged, and the inorganic framework is unaltered as one varies the organic intercalate. The magnetic behaviour of the materials has also been explored using a SQUID magnetometer. In the manganese tungstate hybrids an antiferromagnetic (AF) transition is observed, which decreases in temperature as the inorganic interlayer spacing is increased. A nickel tungstate hybrid sample, on the other hand, displays a ferromagnetic transition, which we attribute to a canted AF phase below 15 K. In all cases studied, the behaviour can be mapped to an effective moment (P^eff) per transition metal ion, which agrees well with theoretical and literature values for other transition metal oxides.