A5089901567- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Catalytic C–H Functionalization Methods
- Synthesis and Catalytic Reactions
- Photocathodes and Microchannel Plates
- Catalytic Cross-Coupling Reactions
- Radiation Therapy and Dosimetry
- Metal-Catalyzed Oxygenation Mechanisms
- Crystallography and molecular interactions
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Sulfur-Based Synthesis Techniques
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Asymmetric Hydrogenation and Catalysis
- Metal complexes synthesis and properties
- Oxidative Organic Chemistry Reactions
- Porphyrin and Phthalocyanine Chemistry
- Vanadium and Halogenation Chemistry
- Electron and X-Ray Spectroscopy Techniques
- Plasma Diagnostics and Applications
- Intracranial Aneurysms: Treatment and Complications
- Topological Materials and Phenomena
- Radical Photochemical Reactions
- Lubricants and Their Additives
Brookhaven National Laboratory
2022-2024
Indian Institute of Technology Madras
2024
Texas Tech University
2022
Indian Institute of Technology Bombay
2018-2022
University of Mumbai
2018-2021
Stony Brook University
2019-2021
Tezpur University
2019
Synthetic non-heme iron-oxo and iron-halide complexes promote selective halogenation of the sp<sup>3</sup>-C–H bonds <italic>via</italic> hydrogen atom abstraction halide rebound phenomenon.
Six and seven membered lactones have been synthesized directly from readily available aliphatic acids.
Abstract Distal C−H bond functionalization of heterocycles remained extremely challenging with covalently attached directing groups (DG). Lack proper site for DG attachment and inherent catalyst poisoning by demand alternate routes selective their distal bonds. Utilizing non‐productive coordinating property to hold the heterocycle into cavity a template system in host–guest manner, we report alkylation (C‐5 quinoline thiazole, C‐7 benzothiazole benzoxazole) heterocycles. Upon complexation...
Aziridination has very recently been found to be catalyzed by heme and nonheme Fe enzymes, opening the way biotechnological developments. However, its mechanism is not fully understood owing contrasting behaviors exhibited several catalysts. Indeed, whereas a few catalysts exhibit an activity dominated inductive effects, of others reveal significant even dominant radical delocalization. Therefore, no clear general rationale aziridination yet emerged. Elaborating on our previous studies, we...
Abstract High brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance the beam, which is determined by mean transverse energy (MTE) and laser spot size, one most important parameters determining beam quality. bialkali photocathodes illuminated visible have advantages quantum efficiency (QE) low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in continuous wave (CW) mode at accelerating gradients,...
An efficient method has been developed to afford highly C-5 selective olefination of thiazole derivatives utilizing a bifunctional template in an intermolecular fashion. Coordinative interaction between the substrates and metal chelated backbone plays crucial role high selectivity. Excellent selectivity for position was observed while mono substituted (2- or 4-) even more challenging unsubstituted thiazoles were employed.
Superlattice GaAs photocathodes are vital for producing polarized electron beams the Electron-Ion Collider (EIC) at Brookhaven National Laboratory. The pre-injector EIC requires a 7 nC bunch with least 85% spin polarization from GaAs-based superlattice cathode. doping density of very surface layer cathode needs to be optimized extract high charge beam high-voltage DC gun. axis emitted is longitudinal, and it will rotated transverse direction using two Wien filters, each rotating by 45...
Abstract Achieving site‐selective C−H functionalization of arene is a fundamental challenge, as it mainly controlled by the electronic nature molecules. A chelation‐assisted strategy overcomes selectivity issues utilizing distance and geometry covalently attached directing groups (DGs). This requires stoichiometric DG installation/removal suitable functional group on which to tether DG. Such strategies are ineffective for small heterocycles unless added. Moreover, not judicious choice...
GaAs photocathodes are the primary choice for generating spin-polarized electron beam with high brightness, polarization, and fast polarization reversal. However, it suffers from short lifetime due to highly reactive nature of emission surface, resulting in substantial operational difficulties. Activating a more robust material, such as Cs2Te, shows comparable that Cs–O activation increases robustness Cs2Te layer. previously reported based on Cs–Te suffer 10× lower quantum efficiency (QE)...
The oxygen atom transfer (OAT) reactivity of the non-heme [FeIV (2PyN2Q)(O)]2+ (2) containing sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins. ferryl-oxo complex 2 shows excellent OAT during epoxidations. steric encumbrance and electronic effect influence mechanistic shuttle between pathway I isomerization II (during reaction stereo pure olefins), resulting in a mixture cis-trans epoxide products. In contrast, less hindered...
The high intensity polarized electron source is a critical component for future nuclear physics facilities. electron-ion collider requires gun with higher voltage and bunch charge compared to any existing source. At Brookhaven National Laboratory, we have built an inverted direct current (HVDC) photoemission large cathode size. We report on the performance of GaAs photocathodes in gradient up 16 nC charge. measurements were performed at stable operating gap 300 kV—demonstrating outstanding...
Abstract Distal C−H bond functionalization of heterocycles remained extremely challenging with covalently attached directing groups (DG). Lack proper site for DG attachment and inherent catalyst poisoning by demand alternate routes selective their distal bonds. Utilizing non‐productive coordinating property to hold the heterocycle into cavity a template system in host–guest manner, we report alkylation (C‐5 quinoline thiazole, C‐7 benzothiazole benzoxazole) heterocycles. Upon complexation...
Abstract Aryl rings are ubiquitous in the core of numerous natural product and industrially important molecules thus their facile synthesis is major interest scientific community industry. Although multiple strategies enable access to these skeletons, metal-catalyzed C–H activation promising due its remarkable efficiency. Commercially available organoboron reagents, a prominent arylating partner cross-coupling domain, have also been utilized for direct arylation. Organoborons bench-stable,...
Alkali antimonide photocathodes have wide applications in free-electron lasers and electron cooling. The short lifetime of alkali necessitates frequent replacement the during a beam operation. Furthermore, exposure to mediocre vacuum causes loss photocathode quantum efficiency due chemical reaction with residual gas molecules. Theoretical analyses shown that covering an monolayer graphene or hexagonal boron nitride protects it coarse environment inhibition reactions require ultra-high...
Photocathodes based on GaAs and other III–V semiconductors are capable of producing highly spin-polarized electron beams. GaAs/GaAsP superlattice photocathodes exhibit high spin polarization; however, the quantum efficiency (QE) is limited to 1% or less. To increase QE, we fabricated a photocathode with Distributed Bragg Reflector (DBR) underneath. This configuration creates Fabry–Pérot cavity between DBR surface, which enhances absorption incident light and, consequently, QE. These...
The polarized electron source is a critical component in accelerator facilities such as the electron–ion collider, which requires gun with higher voltage and bunch charge than existing sources. One challenge we faced was surface limit of distributed Bragg reflector GaAs/GaAsP superlattice (DBR-SL-GaAs) photocathode. We suppressed this effect by optimizing doping heat cleaning procedures. achieved up to 11.6 nC beam. In report, discuss performance tests DBR-SL-GaAs photocathode high direct...
Remote C4-H functionalization of
Mixed valent Pd(0)/Pd(II) nano‐sized aggregates supported onto a chemically robust layered zirconium carboxyphosphonate framework is prepared and its catalytic activity in Suzuki‐Miyaura cross coupling reaction explored. The exceptionally high efficacy of the heterogeneous catalyst signified by remarkably short time 2 minutes turnover frequency 1.3 x 10 4 hr −1 . can be recycled several times without significant loss efficacy, while spectroscopic, structural microscopic investigations...
The lifetime of GaAs photocathodes in polarized electron guns is limited due to the delicate activation layer. An atomically clean and smooth surface needed deposit a robust layer, such as Cs2Te, with longer compared traditional (Cs,O) activation. A previous experiment Cs2Te on used heat cleaning temperatures around 400°C avoid an increase roughness [Bae et al., Appl. Phys. Lett. 112, 154101 (2018)]. High-temperature 580°C, which results relatively contamination-free surface, could be one...