Single crystal ESR and optical studies of VO(HPO 4)·0.5H 2O

Abstract

We report single crystal ESR and optical results on VO(HPO 4)·0.5H 2O. Blue, blue-green, and green transparent crystals resulted from the hydrothermal reaction between VOSO 4·3H 2O and phenylphosphonic acid. Single crystal x-ray diffraction and chemical analysis confirmed the identity of the material as VO(HPO 4)·0.5H 2O. Crystals as large as 1mm × 1mm × 0.08mm were grown, making them suitable for ESR and optical experiments. Single crystals of VO(HPO 4)·0.5H 2O were mounted on a two circle goniometer and the six necessary angular measurements were recorded in order to diagonalize the g-tensor and provide the direction cosines. The crystals were indexed such that the crystallographic axes were known with respect to the goniometer. The V +4 (d 1) are paired antiferromagnetically in discreet dimers. The ESR signal results from the thermal population of an excited triplet state. The intensity of the ESR signal as a function of temperature was determined and fit to a thermally accessible triplet equation yielding a singlet-triplet separation of 60.8 cm −1. Optical absorption in the visible and near infrared on single crystals was also employed to assist in the characterization of the nonaxial the g tensor of the individual vanadyl monomers.