Spectroscopic, thermal, magnetic and structural characterization of K3VF6 prepared at room temperature

A straight forward room-temperature synthesis of V(III) containing complex fluoride K3VF6, using KF and vanadium(III) acetylacetonate is reported. The pale green colored powder was characterized by chemical analysis, powder X-ray diffraction; diffuse reflectance spectroscopy, infrared spectroscopy, Raman spectroscopy, differential scanning calorimetry, scanning electron microscopy, photoluminescence spectroscopy, magnetic susceptibility measurements and photoluminescence spectroscopy. The powder X-ray diffraction pattern was fitted in P21/n space group (monoclinic) with a = 12.106 (1) Å, b = 17.685 (0) Å, c = 11.802 (0) Å, β = 92.23° (1). Differential scanning calorimetry showed phase transitions, occurring at 158 °C and 190 °C. In the FT-IR spectrum, characteristic band for the VF63− group was observed at 508 cm−1. The bands observed in the 335–361 cm−1 region and at 504 cm−1 in the room temperature Raman spectrum of K3VF6 corresponded to the F2g and A1g modes, respectively. The ratio of the frequencies (F2g/A1g) observed in the diffuse reflectance spectrum was fitted on the Tanabe-Sugano diagram to determine the Racah parameter B value of 712 cm−1. Magnetic ordering was not observed down to the lowest measured temperature of 5 K.

Fluorination of V(acac)3 by KF in non-aqueous medium yielded complex mixed metal fluoride K3VF6 characterized by the spectroscopic, powder X-ray diffraction and magnetic measurements.Figure optionsDownload as PowerPoint slideHighlights
► Straight forward fluorination of V(acac)3 with KF in methanol at room temperature yielded K3VF6 which did not require intricate and sophisticated setup. The fluorinating agent also acted as the structure directing agent.
► Based on the DSC and spectroscopy characterization, the fluoride complex was identified to be α-form of K3VF6 possessing the cryolite structure.
► K3VF6 did not show any magnetic ordering till 5 K unlike Na3VF6 and (NH4)3VF6.