A new class of Cr(VI)-BPATCH complexes for nanoparticle synthesis

Abstract Hexavalent Cr complexes offer a highly attractive platform for developing new light-emitting materials, water treatment approaches, and drugs, as Cr is readily available on earth, making the technology economically viable. However, it is challenging to form Cr(VI) complexes due to the limited availability of ligands that can bind to the metal. Herein, we report the synthesis of Cr(VI) and Cr(VI) and vanadium-based new complexes, Cr(VI) bis(pyrrole-2-aldehydo) thiocarbohydrazone (BPATCH) and Cr(VI)-V-BPATCH. Detailed characterization of the new complexes via cation exchange column coupled with atomic absorption spectroscopy, ultraviolet-visible spectroscopy (UV-vis), photoluminescence spectroscopy (PL), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), scanning electron microscopy, and energy dispersive x-ray (EDX) is also reported for the first time. Successful formation of the complexes is confirmed by the EDX compositional analysis coupled with FTIR. Both Cr-BPATCH and Cr-V-BPATCH are cationic and mostly amorphous with a foam-like texture. Absorbances at 255 nm and 297 nm, observed for the Cr-BPATCH complex is attributed to the charge transfer in Cr and the peak in the visible blue region observed both in UV–vis and PL is due to the metal-liagnd complexation. Weight losses are observed at 100 °C, 250 °C, and 500 °C for this complex via TGA analysis while XRD analysis revealed an amorphous nature of the complex. The Cr-V complex shows the presence of some crystalline particles of size ∼4.20 μm. A sharp peak for vanadium (V) phase is also observed in the XRD analysis of the complex. TGA analysis reveals weight losses at 300 °C and 470 °C and a strong complexation between the organic ligand, BPATCH and the metals. We also demonstrate the successful synthesis of Cr 2 O 3 nanoparticles of sizes ∼1.01 ± 0.04 nm and 17.6 ± 7.3 nm with the new Cr(VI)-BPATCH complex. The Cr 2 O 3 nanoparticles exhibit a rhombohedral phase, as suggested from XRD analysis. FTIR characterization revealed oleylamine and BPATCH ligand coating on the nanoparticles. We also report the detailed PL characterization for the size-controlled nanoparticle samples.