9 results on '"Choudhury, Angshuman Roy"'
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2. N-coordinated Ru(II) catalyzed solvent free N-alkylation of primary amines with alcohols through borrowing hydrogen strategy.
- Author
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Patel, Bhavya, Ranjan, Rishi, Chauhan, Nimesh R., Mukhopadhyay, Suman, Choudhury, Angshuman Roy, and Vyas, Komal M.
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ALCOHOL ,ALKYLATING agents ,AMINES ,ELEMENTAL analysis ,X-ray diffraction ,SINGLE crystals - Abstract
Borrowing hydrogenation (BH) is a powerful methodology, which is widely adopted for the N-alkylation of amines with alcohols using homogeneous molecular catalysts. To explore the chemistry, herein two novel monomeric Ru(II) complexes [(η
6 -p-cymene)Ru(L1)Cl2 ] [Ru-1] bearing 4-trifluromethoxyaniline (L1) and [(η6 -p-cymene)Ru(L2)Cl] [Ru-2] bearing quinaldic acid (L2) were synthesized and their structural features were revealed by utilizing analytical and spectroscopic methods like FTIR,1 H and13 C NMR, ESI-MS, and elemental analysis. The lattice structures of both [Ru-1] and [Ru-2] were elucidated by Single Crystal XRD (SC-XRD). Also, aniline-based complex [Ru-3] was synthesized according to the literature and used for comparison. The catalytic efficacy of [Ru-(1–3)] was examined for N-alkylation of amines utilizing alcohols as alkylating agents in benign and solvent-free conditions. The catalytic performance was monitored by GC–MS and HPLC analyses. The primary amine-based (L1) complex [Ru-1] showed a very impressive and efficient conversion of 96%, whereas –N, O donor ligand based (L2) complex [Ru-2] and the unsubstituted aniline based [Ru-3] were able to achieve 25% and 90% conversion, respectively in similar reaction conditions. This drastic variation in catalytic performance was observed due to the co-operative effect of –NH2 in [Ru-1] and [Ru-3]. Metal–ligand cooperation (MLC) in both the complexes stabilizes the intermediate transition state and also the electron deficient Ru(II) center in [Ru-1] has very good binding affinity towards the substrate, which leads to superior catalytic conversion with [Ru-1] compared to [Ru-2] and [Ru-3]. [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. Synthesis, in vitro anti-plasmodial potency, in-silico-cum-SPR binding with inhibition of PfPyridoxal synthase and rapid parasiticidal action by 3,5-bis{(E) arylidene}-N-methyl-4-piperidones.
- Author
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Rokkam, Siva Kumar, Yadav, Mamta, Joshi, Mayank, Choudhury, Angshuman Roy, Sahal, Dinkar, and Golakoti, Nageswara Rao
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SINGLE crystals ,CONFORMITY - Abstract
Twenty-five (Ia–Iu, IIa–IIb, IIIa, and IVa) diarylidene-N-methyl-4-piperidones (DANMPs) were synthesized and characterized via UV, FT-IR, NMR, and MS while Id was characterized also by single crystal XRD. Twenty-one compounds shortlisted after initial in vitro anti-plasmodial activity successive screenings at 100 μM and 10 μM were evaluated for their IC
50 s against chloroquine-sensitive Pf3D7, chloroquine-resistant PfINDO, and artemisinin-resistant PfMRA-1240 strains. The four most promising compounds were Ie (IC50 s μM 0.35MRA , 1.39INDO , 1.923D7 ), If (IC50 s μM 1.07MRA , 1.36INDO , 3.393D7 ), Ir (IC50 s μM 0.74MRA , 2.45INDO , 1.443D7 ), and In (IC50 s μM 1.27MRA , 1.8INDO , 1.73D7 ). Resistance indices as low as 0.2 to 0.5 for these potent compounds and <1 for most other compounds suggest their greater potency against drug resistant strains than the drug sensitive strain. The parasiticidal action of Ir was seen within 4 h against the trophozoite stage of the parasite, which is known to express the highest levels of PLP synthase. In silico docking scores of −7.0 to −8.0 kcal mol−1 between potent DANMPs and PfPLP synthase, the direct binding of Ir studied by SPR to recombinantly expressed and purified PfPdx-1 and inhibition of Pdx1 enzymatic activity by Ir suggest this vital enzyme to be a probable target for the DANMPs. The non-hemolytic nature of Ir and conformity of most DANMPs to Lipinski's parameters indicate their potential as new anti-plasmodial leads with PfPLP synthase as one of their targets. [ABSTRACT FROM AUTHOR]- Published
- 2021
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4. Two‐Coordinate Cu(I) and Au(I) Complexes Supported by BICAAC and CAAC Ligands.
- Author
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Manar, Krishna K., Chakrabortty, Soumyadeep, Porwal, Vishal Kumar, Prakash, Darsana, Thakur, Sandeep Kumar, Choudhury, Angshuman Roy, and Singh, Sanjay
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FRONTIER orbitals ,LIGANDS (Chemistry) ,CRYSTAL structure ,MASS spectrometry ,SINGLE crystals ,COORDINATION compounds - Abstract
Two‐coordinate Cu(I) and Au(I) complexes supported by bicyclic (alkyl)(amino)carbene, [BICAAC‐CuCl] (1), [BICAAC‐CuI] (2), [(BICAAC)2Cu]+[PF6]– (3) and [(BICAAC)2Au]+[AuCl2]– (6) have been synthesized. The reaction of cyclic (alkyl)(amino)carbene, CAACcy with CuCl afforded [CAACcy‐CuCl] (4) and its further reaction with KPF6 gave [(CAACcy)2Cu]+[PF6]– (5). Complexes 1–6 have been characterized by multinuclear NMR, IR and UV‐Vis. spectroscopic method and high‐resolution mass spectrometry (HRMS). Single crystal X‐ray structure of heteroleptic complexes 1 and 4 and homoleptic complexes [(BICAAC)2Cu]+[CuI2]– (2'), 3 and 6 have also been determined. The crystal structure of these complexes confirmed linear two‐coordinate geometry around the metal centers. In the solid‐ state, complexes 1, 2', 4 and 6 displayed C−H⋯M (M=Cu, Au) and weak non‐covalent C−H⋯X (X=Cl, I) and C−H⋯H−C interactions. Computational calculations correlate well to the experimentally observed geometry and help elucidate the absorption characteristics type of transitions and the frontier orbitals involved in them. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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5. Chiral Bent‐Shaped Molecules Exhibiting Unusually Wide Range of Blue Liquid‐Crystalline Phases and Multistimuli‐Responsive Behavior.
- Author
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Punjani, Vidhika, Mohiuddin, Golam, Kaur, Supreet, Choudhury, Angshuman Roy, Paladugu, Sathyanarayana, Dhara, Surajit, Ghosh, Sharmistha, and Pal, Santanu Kumar
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CRYSTALS ,MOLECULAR conformation ,CRYSTAL structure ,AMORPHOUS substances ,DIPOLE moments - Abstract
Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent‐shaped systems with a −CH3 moiety placed at the transverse position of the central core was reported. Herein, a homologous series of compounds with even‐numbered carbon chains from n=4 to 18 were synthesized, in which −Cl was substituted for −CH3 at the kink position and a drastic modification in the phase structure of the bent‐shaped molecule was observed. An unusual stabilization of the cubic blue phase (BP) over a wide range of 16.4 °C has been witnessed. Two homologues in this series (1‐12 and 1‐14) exhibit an interesting phase sequence consisting of BPI/II, chiral nematic, twist grain boundary, smectic A, and smectic X (SmX) phases. The higher homologues (1‐16 and 1‐18) stabilize the SmX phase enantiotropically over the entire temperature range. Crystal structure analysis confirmed the bent molecular architecture, with a bent angle of 148°, and revealed the presence of two different molecular conformations in an asymmetric unit of compound 1‐4. A DFT study corroborated that the −Cl moiety at the central core of the molecule led to an increase in the dipole moment along the transverse direction, which, in turn, facilitated the unusual stabilization of frustrated structures. Crystal polymorphism has been evidenced in three homologues (1‐10, 1‐12, and 1‐14) of the series. On the application of mechanical pressure through grinding, compound 1‐10 transformed from a bright yellow crystalline solid to a dark orange–green amorphous solid, which reversed upon dropwise addition of dichloromethane, indicating reversible mechanochromism in this class of compounds. In addition, excellent thermochromic behavior has been observed for compound 1‐10 with a controlled temperature–color combination. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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6. Reactions of a BICAAC with hydroboranes: propensity for Lewis adduct formation and carbene insertion into the B–H bond.
- Author
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Manar, Krishna K., Porwal, Vishal Kumar, Kamte, Rohit S., Adhikari, Manu, Thakur, Sandeep Kumar, Bawari, Deependra, Choudhury, Angshuman Roy, and Singh, Sanjay
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NUCLEAR magnetic resonance spectroscopy ,BORANES ,SINGLE crystals ,BORON isotopes ,X-ray diffraction - Abstract
The reactivity of a bicyclic (alkyl)(amino)carbene (BICAAC) towards different boranes has been examined in the present work. The reactions with boranes BX
3 ·SMe2 (X = H, Cl, Br), BF3 ·OEt2 and BCl3 yield Lewis adducts [BICAAC·BH3 ] (1), [BICAAC·BHCl2 ] (2), [BICAAC·BH2 Cl] (3), [BICAAC·BF3 ] (4), [BICAAC·BCl3 ] (5) and [BICAAC·BBr3 ] (6) respectively, whereas more hydridic boranes, 9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane (HBcat), enable the insertion of the carbene carbon into the B–H bond to form [BICAAC(H)-(9-BBN)] (7) and [BICAAC(H)-Bcat] (8). These complexes are the first examples of BICAAC–boron compounds and have been characterized using IR, multinuclear NMR spectroscopy, HRMS spectrometry and single crystal X-ray diffraction. Computational analyses were also performed to gain insight into the mechanism of B–H bond activation and adduct formation. Furthermore, the reactions of the BICAAC with boranes have been compared with the known reactions of CAACs and NHCs. [ABSTRACT FROM AUTHOR]- Published
- 2019
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7. Catalytic promiscuity of an iron(II)-phenanthroline complex.
- Author
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De, Abhranil, Garai, Mamoni, Yadav, Hare Ram, Choudhury, Angshuman Roy, and Biswas, Bhaskar
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IRON compounds ,PHENANTHROLINE ,METAL complexes ,X-ray diffraction ,METAL catalysts ,SINGLE crystals - Abstract
A mononuclear iron(II) complex, [Fe(phen)
3 ]Cl2 ( 1) (phen =1,10-phenanthroline), has been synthesized in crystalline phase and characterized using various spectroscopic techniques including single crystal X-ray diffraction. Crystal structure analysis revealed that 1 crystallizes in a monoclinic system with C2/m space group. Complex 1 acts as a functional model for a biomimetic catalyst promoting the aerobic oxidation of 3,5-di- tert-butylcatechol (3,5-DTBC) through radical pathways with a significant turnover number ( kcat =3.55 × 103 h−1 ) and exhibits catechol dioxygenase activity towards the same 3,5-DTBC substrate at room temperature in oxygen-saturated ethanol medium. The existence of an isobestic point at 610 nm from spectrophotometric data indicates the presence of Fe3+ −3,5-DTBC adduct favouring an enzyme-substrate binding phenomenon. Upon stoichiometric addition of 3,5-DTBC pretreated with two equivalents of triethylamine to the iron complex, two catecholate-to-iron(III) ligand-to-metal bands (575 and 721 nm) are observed and the in situ generated catecholate reacts with dioxygen ( kobs =9.89 × 10−4 min−1 ) in ethanol medium to afford exclusively intradiol cleavage products along with a small amount of benzoquinone, and a small amount of extradiol cleavage products, which provide substantial evidence for a mechanism. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]- Published
- 2017
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8. Catalytic aspects of a nickel(II)–bipyridine complex towards phosphatase and catechol dioxygenase activity.
- Author
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Garai, Mamoni, Dey, Dhananjay, Yadav, Hare Ram, Choudhury, Angshuman Roy, Kole, Niranjan, and Biswas, Bhaskar
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PHOSPHATASES , *CATECHOL , *DIOXYGENASES , *SINGLE crystals , *X-ray diffraction , *SPACE groups - Abstract
A mononuclear nickel(II) complex, [Ni(bpy) 2 (OH 2 )(NO 3 )](NO 3 ) ( 1 ) [bpy = 2,2′-bipyridine], has been synthesised and structurally characterised by routine analytical techniques including a single crystal X-ray diffraction study. X-ray crystal structure analysis shows that 1 crystallises in the triclinic system with the P 1 ¯ space group and adopts an octahedral geometry. The nickel(II) complex has been evaluated as a functional model for phosphatase and catechol dioxygenase enzymes by using 4-nitrophenylphosphate (PNPP) and 3,5-di- tert -butylcatechol (DTBC) as model substrates in aqueous-DMF and acetonitrile media respectively. This mononuclear nickel complex exhibits good hydrolytic phosphoester cleavage efficiency, viz. a k cat value of 8.42 × 10 3 h −1 , and produces mostly benzoquinone ( k obs = 2.3 × 10 −3 min −1 ) and intradiol cleavage products during an investigation of catechol dioxygenase activity. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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9. Concise access to aluminum containing [3.3](2,6)pyridinophane and molecular bowl using 2,6-diamidopyridine modules.
- Author
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Negi, Chandrakala, Bawari, Deependra, Thakur, Sandeep Kumar, Choudhury, Angshuman Roy, and Singh, Sanjay
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SINGLE crystals , *ALUMINUM , *X-ray diffraction , *STOICHIOMETRY - Abstract
By varying the relative stoichiometry of the building block bis(trimethylsilyl)–N,N′–2,6–diaminopyridine (bap) and EtAlCl 2 or AlCl 3 , different molecular entities (mononuclear and dinuclear complexes, pyridinophane and molecular bowl) containing aluminum centres have been synthesized. Efforts to extend the approach to synthesize triazinophanes with bis(trimethylsilyl)-N,N′-2,4-diamino‒6‒(R)‒triazines (R = Me, NH(SiMe 3), Ph) in their reactions with AlMe 3 showed strong preference for the formation of dinuclear aluminum complexes over the analogous pyridinophane like structures. All the new compounds have been fully characterized using multinuclear NMR, HRMS and single crystal X-ray diffraction. Image 1 • Pyridinophanes containing aluminum bridged bis(SiMe 3)–N,N'–2,6–diamidopyridine (bap) have been assembled. • By varying the relative stoichiometry of bap and EtAlCl 2 , mononuclear and dinuclear Al complexes have been synthesized. • Dinuclear Al complexes are obtained with bis(SiMe 3)-N,N'-2,4-diamino‒6‒(R)‒triazine (R = Me, NH(SiMe 3), Ph) and AlMe 3. • All the compounds have been characterized by multinuclear NMR, HRMS and single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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