Yashraj Gartia

Magnetic nanoparticles as contrast agents in biomedical imaging: recent advances in iron- and manganese-based magnetic nanoparticles.

Abstract Improvements in diagnostic measures for biomedical applications have been investigated in various studies for better interpretations of biological abnormalities and several medical conditions. The use of imaging techniques, such as magnetic resonance imaging (MRI), is widespread and becoming a standard procedure for such specialized applications. A major avenue being studied in MRI is the use of magnetic nanoparticles (NPs) as contrast agents (CAs). Among various approaches, current research also incorporates use of superparamagnetic iron oxide NPs and manganese-based NPs with biocompatible coatings for improved stability and reduced biodegradation when exposed to a biological environment. In this review, recent advances with these types of magnetic NPs and their potential use as CAs in MRI are reported, as well as new insights into the selectivity and cellular transport mechanism that occurs following injection.

Synthesis and characterization of Co(III) amidoamine complexes: influence of substituents of the ligand on catalytic cyclic carbonate synthesis from epoxide and carbon dioxide

A series of amidoamine ligands (1) and their cobalt(III) complexes (2) were synthesized and characterized by various spectroscopic techniques including (1)H-NMR and X-ray crystallographic techniques. X-ray crystallography shows that one of the complexes, 2a, forms a chiral coordination polymer due to bridge formation with Li(+) associated with the complex, although the ligand is achiral. Complex 2 was employed for catalytic synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2) in a solvent free condition. A strong influence of the substituents on the ligand 1 was revealed by the varied activity of complex 2. The presence of electron withdrawing groups such as chloro (2b) and nitro (2c) increases the Lewis acidity of the catalyst, which, in turn, enhances the catalytic activity of 2. An electron withdrawing group containing complexes (2b and 2c) showed exceptionally high catalytic activity with a turnover frequency (TOF) of 662 and 602 h(-1) respectively at 130 °C and 300 psig CO2 pressure. On the other hand, our studies indicate that a catalyst with an electron releasing group (2d) showed relatively lower activity with a TOF of 488 h(-1) under similar reaction conditions. Our results show that cobalt(iii) complexes follow the reactivity order of 2d < 2a < 2c < 2b.

Nickel Complex Catalyzed Efficient Activation of sp3 and sp2 C–H Bonds for Alkylation and Arylation of Oxygen Containing Heterocyclic Molecules

A nickel(II) complex (1) of N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamido (L) ligand was examined for catalytic coupling of Grignard reagents with the C–H bond of oxygen containing heterocyclic compounds such as tetrahydrofuran and furan. The nickel(II) complex showed excellent activity in catalyzing C–H activation and further coupling with various Grignard reagents. The effective activation of the C–H bond proceeded under ambient reaction conditions with a short reaction time (1–2xa0h). The catalyst (1) displays high turnover frequency of 4,130xa0h−1 with catalyst loading as low as 0.01xa0mol%. This catalytic route could prove to be an efficient mode of activation of sp3 and sp2 C–H bonds in various heterocycles for the preparation of synthetically and pharmaceutically relevant molecules.Graphical Abstract

A Novel Iron Complex for Cross-Coupling Reactions of Multiple C–Cl Bonds in Polychlorinated Solvents with Grignard Reagents

A novel iron(III) complex (2) of a pincer ligand [1, N2,N6-bis(2,6-diisopropylphenyl)pyridine-2,6-dicarboxamide] was developed and used for remediation of polychlorinated solvents via sp3–sp3 coupling of Grignard reagents with C–Cl bonds. The use of an iron catalyst for such coupling reactions is highly desirable due to its greener and more economical nature. Complex 2 was characterized using various spectroscopic techniques: electrospray ionization mass spectrometer (ESI-MS, m/z 575.1), cyclic voltammetry (E1/2, 0.03xa0V and ∆E, 0.97xa0V), and ultraviolet visible (UV/Vis) spectroscopic techniques. The iron(III) complex showed efficient activation of multiple C–Cl bonds and catalyzing C–C coupling of polychlorinated alkyl halides, such as dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), with various Grignard reagents under ambient reaction conditions. Complex 2 showed exceptional activity with reactions approaching near completion in about 5xa0min. With the required catalyst loading as low as 0.2xa0mol%, considerably high turnover numbers (TONxa0=xa0483) and turnover frequency (TOFxa0=xa05,800xa0h−1) were obtained. None of the products detected during the reaction contained any chlorine, indicating an efficient dechlorination method while synthesizing products of synthetic and commercial interest. Interestingly, the catalyst was capable of replacing all chlorine atoms in each polychlorinated solvent under the investigations with high conversion.Graphical Abstract

Determination of bile acid profiles in scat samples of wild animals by liquid chromatography-electrospray mass spectrometry

A practical and accurate analytical method using liquid chromatography-mass spectrometry (LC-MS) was developed to determine the bile acid profile in the scat samples of various wild animals such as mountain lion, bobcat, coyote, raccoon, fox, etc. Bile acid extraction from the scat sample of the wild animals and its detection using the LC-MS technique are very easy and can be done in a short period of time with good resolution. The bile acid profiles are different in each species and the analytical method is very effective in identifying the wild animals under investigation. The detection limits of all bile acids were very low (∼1.0 ng mL−1) and the analytical method provides excellent reproducibility.