From 4'-Hydroxy-2,2':6',2''-Terpyridine Complex of Chromium(III) towards Cr2O3 Nanoparticles: Effects of the Calcination Temperature on the Particle Size and Morphology

A new chromium(III) complex containing 4ʹ-hydroxy-2,2ʹ:6ʹ,2ʺ-terpyridine (tpyOH) has been prepared by the reaction of CrCl3. 6H2O with tpyOH in the presence of metallic zinc to afford the new complex [CrCl3(tpyOH)] (1). The complex 1 was used as a suitable precursor for the preparation of Cr2O3 nanoparticles by the simple calcination method at three different annealed temperatures of 400, 600, and 800 ˚C. The structures of the products have been fully characterized by IR, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The average particle size using Scherrer’s equation is calculated to be about 27-36 nm. The results suggest that temperature is an effective way to tailor the morphology and crystallinity of the prepared nanoparticles. The photophysical properties and thermal gravimetric analysis (TGA) of the complex 1 have also been investigated. The emission of 1 exhibits the high-energy intense π→π* intraligand and low-energy MLCT transitions in DMSO solution. The TGA results show the stability of the complex up to 400 ˚C after stepwise decomposition of the coordinated ligands.