Department of Chemistry
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Item Steroid-triazole conjugates: A brief overview of synthesis and their application as anticancer agents(Elsevier, 2023-09) Sakhuja, RajeevSteroids are biomolecules that play pivotal roles in various physiological and drug discovery processes. Abundant research has been fuelled towards steroid-heterocycles conjugates over the last few decades as potential therapeutic agents against various diseases especially as anticancer agents. In this context various steroid-triazole conjugates have been synthesized and studied for their anticancer potential against various cancer cell lines. A thorough search of the literatures revealed that a concise review pertaining the present topic is not compiled. Therefore, in thus review we summarize the synthesis, anticancer activity against various cancer cell lines and structure activity relationship (SAR) of various steroid-triazole conjugates. This review can lay down the path towards the development of various steroid-heterocycles conjugates with lesser side effects and profound efficacy.Item Facile synthesis of ZnO/ZnS hollow nanorods via Kirkendall effect with enhanced photocatalytic degradation of methylene blue(Springer, 2023-03) Pande, SurojitBecause of the growing concerns about environmental issues, the search of proficient semiconductor catalysts for pollutants degradation from contaminated water is one of the interesting areas of research. Due to the larger surface area, hollow nanomaterials with hollow interior and outer thickness illustrate a class of significant nanostructured materials. The enhanced surface area provides remarkable applications of the hollow nanomaterials in catalysis. In Kirkendall effect, pores are formed owing to the diverse diffusion rates of two nanomaterials in a diffusion couple. Here, we have introduced the facile hydrothermal synthesis of hollow nanorods of ZnO/ZnS via Kirkendall effect using ZnO nanorods (NRs). The morphologies, optical properties, compositions, and crystal structures of the as synthesized materials are systematically studied using UV–vis, PXRD, FESEM, TEM, EDS, XPS, etc. The process of synthesis and growth mechanism of hollow NRs is suggested based on the Kirkendall effect. A hollow nanomaterial, envisaged being highly efficient for molecule adsorption on its surface, the as synthesized materials were used for the photocatalytic degradation of methylene blue (MB) dye. MB degradation efficiency of 96% within 60 min was performed over ZnO/ZnS hollow NRs, which was 2.6-fold greater than that of ZnO. The rate constant of ZnO/ZnS heterostructure was 0.045 min−1, which was 5.5 times larger than that of bare ZnO. We have concluded our work in the directions towards the synthesis of various semiconductor hollow nanostructures for the varied catalytic reactionsItem CO2 to Cyclic Carbonate: A Mechanistic Insight of a Benign Route Using Zinc(II) Salophen Complexes(Wiley, 2023-12) Ray, SaumiZinc(II) Schiff base complexes with different substituents at 5, 5’ positions have been synthesized to study the effect of the electronic environment of the metal towards the cycloaddition reaction between CO2 and epoxide. The complexes have been characterized by FT-IR, XPS, NMR, electronic spectroscopy, LC–MS, and TGA. We have used density functional theory to study the electronic structure of the Zn(II) complexes and modelled the electronic spectra and the mechanism of catalysis. Results obtained from DFT and LC–MS indicate the dimeric structures for all the complexes except ZnL4. The monomeric ZnL4 has the strongest electron withdrawing group, i. e., −NO2 at 5, 5’ positions along with two labile water molecules attached to the Zn center. The dimeric complexes exhibit good to moderate yield for cycloaddition reaction to styrene carbonate under solvent-free conditions and a relatively low reaction temperature of 80 °C, with CO2 pressure of ~1 atm. The best yield has been achieved by ZnL4. Different rate-determining steps are captured by the DFT studies for dimeric and monomeric complexes. Without taking any preventing measure of dimerization by attaching the bulky tBu groups, relatively lesser catalytic amounts of all the complexes have shown yields of cyclic carbonate between 53–74 %, depending on the nature of the substituent present.Item Regiodivergent Synthesis of Cinnoline-Fused Indazolones through Pd-Catalyzed Annulation of 1-Arylindazolones with Allenoates(ACS, 2022-01) Sakhuja, RajeevA tender-hearted Pd(II)-catalyzed C–H activation of 1-arylindazolones followed by an oxidative [4 + 2] annulation reaction has been accomplished, engaging allenoates as annulating partners. Using this strategy, two different regioisomeric forms of cinnoline-fused indazolones possessing internal and exocyclic double bonds were synthesized in acetic acid and dioxane, respectively. Mild and aerobic conditions, avoiding the use of any metal–oxidant, highlights the rewards of this oxidative annulation protocol.Item Development of Isatin-Based Schiff Bases Targeting VEGFR-2 Inhibition: Synthesis, Characterization, Antiproliferative Properties, and QSAR Studies(Wiley, 2022-05) Sakhuja, RajeevThree sets of isatin-based Schiff bases were synthesized utilizing the molecular hybridization approach. Some of the synthesized Schiff bases show significant to moderate antiproliferative properties against MCF7 (breast), HCT116 (colon), and PaCa2 (pancreatic) cancer cell lines with potency compared to reference drugs 5-fluorouracil (5-FU) and Sunitinib. Among all, compound 17 f (3-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1-((1-(2-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)-5-methylindolin-2-one) exhibits promising antiproliferative properties against the MCF7 cancer cell line with 2.1-fold more potency than Sunitinib. However, among all the synthesized compounds, three (5-methylisatin derivatives) were the most effective against HCT116 in comparison to 5-FU. Compound 17 f exhibited the highest anti-angiogenic effect on the vasculature as it significantly reduced BV from 43 mm to 2 mm in comparison to 5.7 mm for Sunitinib and flow cytometry supports the arrest of the cell cycle at G1/S phases. In addition, compound 17 f also showed high VEGFR-2 inhibition properties against breast cancer cell lines. Robust 2D-QSAR studies supported the biological data.Item Two pillared-layer metal–organic frameworks based on the pinwheel trinuclear carboxylate-clusters of Zn(II) and Co(II): synthesis, crystal structures, magnetic study, and Lewis acid catalysis(RSC, 2023) Sarkar, MadhushreeUsing a dicarboxylic acid, [1,1′-biphenyl]-4,4′-dicarboxylic acid (H2L1) and an exobidentate ligand, (1E,1′E)-N,N′-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) (L2), two 3D interpenetrated networks, {[Zn3(L1)3(L2)]·9H2O}n (Zn-MOF) and {[Co3(L1)3(L2)(DMF)]·0.5DMF}n (Co-MOF), have been prepared in good yields. The crystal structure analysis of Zn-MOF and Co-MOF revealed that both have a 3D pillared-layer structure based on pinwheel trinuclear metal–carboxylate clusters as secondary building units (SBUs). Furthermore, the structures also exhibited three-fold interpenetration. Although the overall networks in Zn-MOF and Co-MOF showed significant resemblances, there are marked differences in their crystal structures, which are associated with the coordination environment of the metal centre and the binding modes of the carboxylates. Gas adsorption studies (N2 at 77 K and 1 bar) indicated that Co-MOF is more porous than Zn-MOF. Magnetic measurements on Co-MOF indicate a significant antiferromagnetic interaction (45 K to 303 K) between trimeric Co(II) S = 3/2 spins through syn–syn carboxylato bridges. Both MOFs were studied for the Lewis acid catalyzed Knoevenagel condensation reactions between benzaldehydes and malononitrile with an active methylene group, where Zn-MOF was found to be a better catalyst than Co-MOF. This was supported by the Monte Carlo simulations indicating the better substrate binding ability of Zn-MOF than Co-MOF.Item Direct catalytic synthesis of β-(C3)-substituted pyrroles: a complementary addition to the Paal–Knorr reaction(RSC, 2021) Kumar, IndreshThe synthesis of β-(C3)-functionalized pyrroles is a challenging task and requires a multistep protocol. An operationally simple direct catalytic synthesis of β-substituted pyrroles has been developed. This one-pot multicomponent method combined aqueous succinaldehyde as 1,4-dicarbonyl, primary amines, and isatins to access hydroxyl-oxindole β-tethered pyrroles. Direct synthesis of the β-substituted free NH-pyrrole is the central intensity of this work. DFT-calculations and preliminary mechanism investigation support the possible reaction pathway.Item Two-pot synthesis and photophysical studies of 1,6-disubstituted 5-aza-indoles from succinaldehyde and N-aryl propargylic-imines(RSC, 2021) Kumar, IndreshA two-pot synthesis of 5-aza-indoles has been developed from aqueous succinaldehyde and N-aryl propargylic-imines. This overall protocol involves: (i) the metal-free [3 + 2] annulation of aqueous succinaldehyde and N-aryl propargylic-imines to access 2-alkynyl-pyrrole-3-aldehydes and (ii) Ag-catalyzed 6-endo-dig-cyclization to obtain substituted 5-aza-indoles in the second pot. The 5-aza-indoles showed engaging photophysical activities, and the practicality of this pot-economic gram-scale synthesis has been demonstrated.Item Synthesis of Red-Light-Responsive Pheophorbide-a Tryptamine Conjugated Photosensitizers for Photodynamic Therapy(Wiley, 2022-11) Kumar, DalipSix methyl pheophorbide-a derivatives were prepared by linking a tryptamine side chain at the C-131, C-152 and C-173 positions of pheophorbide-a. Prepared conjugates were characterized and evaluated for their photocytotoxicity against A549 cells. The conjugate 6 a with strong absorption at 413 nm (Soret band), 663–671 nm (Q bands) and comparable fluorescence quantum yield (0.26) was found to exhibit significant cytotoxicity (659 nM). Molecular integration of pheophorbide-a and tryptamines showed synergistic effects as the most potent conjugate 6 a was identified with enhanced photocytotoxicity when compared to methyl pheophorbide-a. The conjugate 6 a was smoothly taken up by A549 cells and exhibited intracellular localization predominantly to lysosome in the cytoplasm. Upon photoirradiation 6 a generated singlet oxygen to show potent cytotoxicity toward A549 cells.Item Luminescent triazolo-fused pyrido[3,4-b]pyrazines as novel fluorophores(Elsevier, 2024-12) Khungar, Bharti; Sakhuja, RajeevA series of organic fluorophores based on novel [1,2,4]triazolo [4′,3':1,2]pyrido [3,4-b]pyrazine architecture were synthesized by a simple two-step protocol. Synthesized organic fluorophores exhibit blue-to-green fluorescence and their UV absorption and fluorescent emission properties were studied. The photophysical properties of synthesized derivatives were tuned by introducing functionalities of varying electronic nature on the core nucleus. The luminescence maxima of the synthesized compounds are found in the range from 427 nm to 503 nm, and the quantum yields ranging from 0.01 to 0.64 were calculated. Among various synthesized molecules, 3-(4-bromophenyl)-8,9-bis(4-methoxyphenyl)-[1,2,4]triazolo [4′,3':1,2]pyrido [3,4-b]pyrazine showed highest quantum yield (ΦF = 0.64), and was further explored for its solvatochromic, acidochromic, aggregation induced fluorescence studies along with theoretical HOMO-LUMO calculations