Kovuru Gopalaiah

Anion (Fluoride)-Doped Ceria Nanocrystals: Synthesis, Characterization, and Its Catalytic Application to Oxidative Coupling of Benzylamines

Fluoride doping in the CeO2 lattice has been achieved by a simple, reliable, reproducible, and safe solution-based method. F-containing CeO2 has retained the fluorite structure, and its effect has been confirmed from various analytical techniques such as powder X-ray diffraction, Fourier transform IR, Raman, UV-visible diffuse reflectance, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy-dispersive X-ray (EDX) and transmission electron microscopy-EDX analysis. The concentration of fluoride in the CeO2 lattice has been determined from chemical analysis and core-level XPS analysis. The concentration of Ce(3+) in the F-doped and undoped CeO2 samples have been determined both from XPS analysis as well as from variable-temperature magnetic susceptibility measurements. The characteristic Ce(3+) emission in the PL spectrum indicated the increase of Ce(3+) ion concentration in the F-doped sample, conforming to the results from XPS and magnetic measurements. F-doped CeO2 nanocrystals showed moderate monodispersity as determined from particle-size measurements using dynamic light scattering experiments and high surface area of 106.1 m(2)/g. Optical band gap of CeO2 has narrowed upon doping with fluoride ions from 3.05 to 2.95 eV. The formation of extrinsic oxygen vacancy complexes upon F-doping has been observed in the Raman spectrum (at 1097 cm(-1)) in addition to fingerprint bands of CeO2. The UV-shielding property and photocatalytic inactivity toward aqueous dye degradation process of F-doped CeO2 has suggested its potential use in cosmetic applications. Both F-doped CeO2 and CeO2 have been used as catalysts for oxidative coupling of benzylamines to imines in the presence of molecular oxygen under solvent-free conditions. F-doped CeO2 exhibited better catalytic efficiency than CeO2. The oxidation procedure using these catalysts is simple, environmentally benign, and solvent-free, and the catalysts are reusable.

Recent Developments in Samarium Diiodide Promoted Organic Reactions

In the early eighties, we introduced samarium diiodide for the transformation of various functional groups. Since then, this reducing agent has been extensively used for the reductive cleavage of single bonds, C-C bond formations, C-N bond formations, and β-elimination reactions. In this Personal Account, we highlight our initial results, as well as some of the contributions from various research groups. Because of space limitations, we arbitrarily select some useful results that have recently been described in literature.

Iron(II) bromide-catalyzed oxidative coupling of benzylamines with ortho-substituted anilines: synthesis of 1,3-benzazoles

An iron(II) bromide-catalyzed oxidative coupling of benzylamines with 2-amino/hydroxy/mercapto-anilines has been developed, allowing the synthesis of a diversity of substituted 1,3-benzazoles in good to excellent yields. This transformation is compatible with a wide range of functional groups. The method is practical, economical and employs molecular oxygen as an oxidant.

Growth, crystal structure, Hirshfeld surface, optical, piezoelectric, dielectric and mechanical properties of bis­(l-asparaginium hydrogensquarate) single crystal

Molecular organic single crystals of bis(L-asparaginium hydrogensquarate) monohydrate [BASQ; (C8H10N2O7)2·H2O] have been grown by solution technique. Crystallographic information was investigated by single-crystal X-ray diffraction (SCXRD) analysis. Hirshfeld surface and fingerprint plot studies were performed to understand the intermolecular interactions of the BASQ crystal in graphical representation. Functional group identification was studied with FT-IR (Fourier transform-IR) spectroscopy. The positions of proton and carbon atoms in the BASQ compound were analyzed using NMR spectroscopy. High transparency and a wide band gap of 3.49 eV were observed in the linear optical study by UV-vis-NIR spectroscopy. Intense and broad photoluminescence emissions at room temperature were observed in blue and blue-green regions. The frontier molecular orbitals of the BASQ molecule were obtained by the DFT/B3LYP method employing 6-311G** as the basis set. The dielectric study was carried out with temperature at various frequency ranges. The piezoelectric charge coefficient (d33) value of BASQ crystal was found to be 2 pC/N, which leads to its application in energy harvesting, mechanical sensors and actuators applications. In the non-linear optical study, the BASQ crystal showed promising SHG conversion efficiency. Mechanical properties of the BASQ crystal were studied experimentally by Vickers microhardness technique, which revealed that the grown crystal belonged to the softer category. BASQ crystal void estimation reveals the mechanical strength and porosity of the material.

A Solvent-Free Process for Synthesis of Imines by Iron-Catalyzed Oxidative Self- or Cross-Condensation of Primary Amines Using Molecular Oxygen as Sole Oxidant

The synthesis of imines by oxidative self- or cross-condensation of primary amines has been achieved using iron(II) bromide as the catalyst. The protocol is ligand-free, additive-free, solvent-free, and high-yielding and utilizes renewable oxygen as sole oxidant. The reaction tolerated a wide range of functionalities.Graphical Abstract

Early history of asymmetric synthesis: who are the scientists who set up the basic principles and the first experiments?

The main classes of asymmetric synthesis are retrieved. Then the historical developments in the attempts to prepare enantiomerically enriched compounds are detailed. The conceptual and experimental contributions of the main pioneers from the time of Pasteur until the First World War have been addressed.