- Vanadium(V) complexes of some bidentate hydrazone ligands and their bromoperoxidase activity
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Dinuclear methoxy bridged complexes of vanadium, [VO(μ-OMe)(OMe)(L)]2(1–3) have been synthesized from the reaction of VOSO4·H2O with triethylamine and the respective hydrazone ligand. The compounds have been characterized by spectroscopic methods and determination of single crystal X-ray structure of one of them (1). DFT and TD-DFT calculations were used to understand the electronic structures of the complexes and their electronic spectra respectively. Though the dimeric complexes are stable in the solid state, the ESI-MS spectra as well as1H NMR spectra of the complexes suggest that in solution the monomeric forms of the complexes are the major species. The V(V) complexes in DMF were used to catalyze the oxidative bromination of salicylaldehyde, in aqueous H2O2/KBr in the presence of HClO4at room temperature. The complexes show exceptionally high bromoperoxidase activity with salicylaldehyde as a model substrate to produce 5-bromo salicylaldehyde in good yield and high TOF and TON. Therefore, these complexes behave as functional models of vanadate dependent bromoperoxidase enzyme.
- Adak, Piyali,Ghosh, Bipinbihari,Pakhira, Bholanath,Sekiya, Ryo,Kuroda, Reiko,Chattopadhyay, Shyamal Kumar
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- Novel D-π-A dye sensitizers of polymeric metal complexes based on Cd(II) with salicylaldehyde and diaminomaleonitrile: Synthesis, characterization, and photovoltaic performance for dye-sensitized solar cells
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Being a key component of dye-sensitized solar cells, dye sensitizer and its synthesis and application have been extensively researched. In this paper, four novel polymeric metal complexes as dye sensitizers based on Cd(II) with salicylaldehyde and diaminomaleonitrile were functionally designed and synthesized. These dyes use poly(p-phenylenevinylene) or bithiophene phenylenevinylene as electron donor, Cd(II) complex unit as electron acceptor, and ethylenic bond as π linker. They were characterized by FT-IR, 1H NMR, gel permeation chromatography, and elemental analysis. Their thermal, photophysical, electrochemical, and photovoltaic properties were also investigated by thermogravimetric analysis, differential scanning calorimetry, C-V curves, and J-V curves. All four polymeric metal complexes exhibited some photovoltaic performances. The dyes containing bithiophene (P2, P4) exhibited higher power conversion efficiency (PCE) values than the corresponding polymers without thiophene unit (P1, P3). Dual-core cadmium polymeric metal complexes showed higher PCE than mononuclear cadmium complexes by comparing P4 with P2 as well as P3 with P1. The highest PCE of compound P4 reached 2.07 % (J sc = 4.22 mA/cm2, V oc = 0.71 mV, and FF = 69.1 %) under simulate AM 1.5G solar irradiation.
- Hu, Jiaomei,Jin, Xueliang,Peng, Dahai,Xie, Qiufang,Liu, Ye,Liao, Yanlong,Zhu, Chunxiao,Zhong, Chaofan
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- Efficient one-pot synthesis of ethyl [2-(2H-Chromene-3yl)-4-oxo-L,3- thiazolidin-3-yl]acetates
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Ethyl [2-(2H-chromene-3yl)-4-oxo-1,3-thiazolidin-3yl]acetates (6a-e) were synthesized in a single pot by the reaction of 2H-3-chromenecarbaldehydes (3a-e), glycine ethyl ester hydrochloride (4), and mercaptoacetic acid (5) in diisopropylethylamine/benzene under refluxing conditions in a Dean-Stark trap.
- Reddy, S. Satyanarayana,Krupadanam, G. L. David
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- Heterogeneous Catalytic Oxidative Bromination and Oxidation of Thioethers By Vanadium(IV) Oxido Complex of Benzoylacetone and Effect of Solid Supports
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Vanadium(IV) oxido complex of 1-Phenyl-1,3-butanedione [VIVO(bzac)2] (1) was prepared, characterized, and heterogenized onto APTMS modified graphene oxide, as well as imidazole modified polystyrene beads. Graphene oxide supported complex GO-APTMS-[VIVO(bzac)2] (2) and polymer anchored complex PS-im-[VIVO(bzac)2] (3) were used for the oxidative bromination of a number of small organic molecules and oxidation of a series of thioethers. Both 2 and 3 evolve as excellent heterogeneous catalysts. The nature of solid support does not impact substrate conversion (%) during the oxidative bromination of salicylaldehyde, phenol, or styrene, whereas it influences the substrate conversion (%) as well as the product selectivity (%) during the oxidation of thioethers. Graphic Abstract: [Figure not available: see fulltext.]
- Kesharwani, Neha,Chaudhary, Nikita,Haldar, Chanchal
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- Copper(II) N, N, O-Chelating Complexes as Potential Anticancer Agents
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Three novel dinuclear Cu(II) complexes based on a N,N,O-chelating salphen-like ligand scaffold and bearing varying aromatic substituents (-H, -Cl, and -Br) have been synthesized and characterized. The experimental and computational data obtained suggest that all three complexes exist in the dimeric form in the solid state and adopt the same conformation. The mass spectrometry and electron paramagnetic resonance results indicate that the dimeric structure coexists with the monomeric form in solution upon solvent (dimethyl sulfoxide and water) coordination. The three synthesized Cu(II) complexes exhibit high potentiality as ROS generators, with the Cu(II)/Cu(I) redox potential inside the biological redox window, and thus being able to biologically undergo Cu(II)/Cu(I) redox cycling. The formation of ROS is one of the most promising reported cell death mechanisms for metal complexes to offer an inherent selectivity to cancer cells. In vitro cytotoxic studies in two different cancer cell lines (HeLa and MCF7) and in a normal fibroblast cell line show promising selective cytotoxicity for cancer cells (IC50 about 25 μM in HeLa cells, which is in the range of cisplatin and improved with respect to carboplatin), hence placing this N,N,O-chelating salphen-like metallic core as a promising scaffold to be explored in the design of future tailor-made Cu(II) cytotoxic compounds.
- Pe?a, Quim,Sciortino, Giuseppe,Maréchal, Jean-Didier,Bertaina, Sylvain,Simaan, A. Jalila,Lorenzo, Julia,Capdevila, Mercè,Bayón, Pau,Iranzo, Olga,Palacios, òscar
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- Mono- and dinuclear oxidovanadium(v) complexes of an amine-bis(phenolate) ligand with bromo-peroxidase activities: Synthesis, characterization, catalytic, kinetic and computational studies
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The mono- and dinuclear oxidovanadium(v) complexes [VVO(L1)(Cl)] (1) and [L1VVO(μ2-O)VO(L1)] (2) of ONNO donor amine-bis(phenolate) ligand (H2L1) were readily synthesized by the reaction between H2L1 and VCl3.(THF)3 or VO(acac)2 in MeOH or MeCN, respectively, and then characterized through mass spectroscopy, 1H-NMR and FTIR techniques. Both the complexes possess distorted octahedral geometry around each V centre. Upon the addition of 1 equivalent or more acid to a MeCN solution of complex 1, it immediately turned into the protonated form, which might be in equilibrium as: [L1ClVVOH]+ ? [L1ClVV-OH]+ (in the case of [L1ClVVOH]+ oxo-O is just protonated, whereas in [L1ClVV-OH]+ it is a hydroxo species), with the shift in λmax from 610 nm to 765 nm. Similar was the case for complex 2. The complexes 1 and 2 could efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo salicylaldehyde as the major product with TONs of 405 and 450, respectively, in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide oxidation reaction indicated a first-order mechanism in the protonated peroxidovanadium complex and a bromide ion and limiting first-order mechanism on [H+]. The evaluated kBr and kH values were 5.78 ± 0.20 and 11.01 ± 0.50 M-1 s-1 for complex 1 and 6.21 ± 0.13 and 20.14 ± 0.72 M-1 s-1 for complex 2, respectively. The kinetic and thermodynamic acidities of the protonated oxido species of complexes 1 and 2 were pKa = 2.55 (2.35) and 2.16 (2.19), respectively, which were far more acidic than those reported by Pecoraro et al. for peroxido-protonation instead of oxido protonation. On the basis of the chemistry observed for these model compounds, a mechanism of halide oxidation and a detailed catalytic cycle are proposed for the vanadium haloperoxidase enzyme and these were substantiated by detailed DFT calculations.
- Debnath, Mainak,Dolai, Malay,Pal, Kaberi,Bhunya, Sourav,Paul, Ankan,Lee, Hon Man,Ali, Mahammad
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- Syntheses and characterization of monobasic tridentate Cu(II) Schiff-base complexes for efficient oxidation of 3,5-di-: tert -butylcatechol and oxidative bromination of organic substrates
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Two monomeric copper complexes [CuII(sal-ppzH)Cl2] (1) and [CuII(hyap-ppzH)Cl2] (2) were synthesized by reacting CuCl2·2H2O with the monobasic tridentate Schiff-base ligands [Hsal-ppz] (I) and [Hyap-ppz] (II) (derived by reacting 1-(2-aminoethyl) piperazine with salicylaldehyde and 2-hydroxyacetophenone) respectively. Elemental analysis, IR, UV-Vis, 1H NMR and 13C NMR data confirm the structures of the ligands and those of the complexes. Both complexes are monomeric in nature in the solid state and in solution as well. Single crystal XRD data suggest a distorted square pyramidal geometry for 1 crystallized in the P1 space group. DFT studies established a similar molecular structure for 2. The synthesized metal complexes [CuII(sal-ppzH)Cl2] (1) and [CuII(hyap-ppzH)Cl2] (2) successfully catalyzed the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) in methanol in the presence of H2O2 with high Kcat values of 1.182 × 104 mmol h-1 and 2.880 × 104 mmol h-1, respectively. [CuII(sal-ppzH)Cl2] (1) and [CuII(hyap-ppzH)Cl2] (2) were also anchored into the polymeric matrix of chloromethylated polystyrene and were analyzed by TGA, atomic absorption spectroscopy (AAS), EPR, scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX) analysis. The polymer grafted metal complexes were used as catalyst precursors in the oxidative bromination of salicylaldehyde in the presence of H2O2, KBr and HClO4. Under optimized reaction conditions, both catalysts show nearly quantitative oxidative bromination of salicylaldehyde, with the order of % products formed being 5-bromosalicylaldehyde > 3,5-dibromosalicylaldehyde > 3-bromosalicylaldehyde. Plausible reactive species involved in the catalytic cycle are identified by UV-Vis spectroscopy, pH metric titration, ESI-MS, EPR and DFT studies.
- Kumari, Sweta,Mahato, Arun Kumar,Maurya, Abhishek,Singh, Vijay Kumar,Kesharwani, Neha,Kachhap, Payal,Koshevoy, Igor O.,Haldar, Chanchal
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- The one pot synthesis salicylaldehyde prepared by reactive grinding with derivative phenol and paraformaldehyde in absence magnesium methoxide
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The formylation phenols are mono-formylated using a mixture of paraformaldehyde, Mg(OMe)2, by reactive grinding. In all cases but one, only one regioisomer of the salicylaldehyde is obtained in good to high yield.
- Balali, Ebrahim,Shameli, Abolghasem,Naeimi, Hoseein,MehdiGhanbari, Mohammad
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- Synthesis and characterization of Azo schiff bases and their β-lactam derivatives
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Azo salicylaldehyde (I5) was synthesized by reaction of 5-bromo-salicylaldehyde with diazonium salt of 4-nitroaniline by diazotization method. Thus, synthesized azoaldehyde was treated with variable 2-aminobenzothiazoles (I6a-f) to synthesize the Schiff bases (I7a-f). The β-lactam derivatives (I8a-f) were also synthesized. All the newly synthesized compounds were characterized by TLC, UV-visible and FT-IR techniques.
- Shinde, Anil H.,Patil
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- Dioxovanadium(V) complexes of ONO donor ligands derived from pyridoxal and hydrazides: Models of vanadate-dependent haloperoxidases
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[VO(acac)2] reacts with H2L [H2L are the hydrazones H2pydx-inh (I), H2pydx-nh (II), or H 2pydx-bhz (III); pydx = pyridoxal, inh = isonicotinohydrazide, nh = nicotinohydrazide, bhz = benzohydrazide] in dry methanol to yield the oxovanadium(IV) complexes [VOL] (H2L = I: 1; H2L = II: 4) or [VO(pydx-bhz)]. These complexes, when exposed to air, convert into the corresponding dioxovanadium(V) complexes [VO2HL] (H2L = I: 2; H2L = II: 5; H2L = III: 7). Aqueous solutions of vanadate and the ligands at pH = 7.5 give rise to the formation of [K(H 2O)3][VO2(pydx-inh)] (3), [K(H 2O)2][VO2(pydx-nh)] (6) and [K(H 2O)2][VO2(pydx-bhz)] (8). Treatment of 6 and 8 with H2O2 generates the oxo(peroxo)vanadium complexes [VO(O2)L] (H2L = II: 9; H2L = III: 10). Complexes 9 and 10 are capable of transferring an oxo group to PPh3. Acidification of 8 with HCl afforded a hydroxo(oxo) complex. The crystal and molecular structures of ligand I and complex 3 have been solved by single-crystal X-ray diffraction. In the anion 3, the vanadium atom is in a distorted tetragonal-pyramidal environment (τ = 0.23). The K+ ion is coordinated to four water molecules (two of which bridge to a neighbouring K+ ion), the pyridine nitrogen atom of an isonicotinic moiety, the equatorial oxo group of the VO2+ fragment, and the alcoholic group of the pyridoxal moiety, which links adjacent layers in the three-dimensional lattice network. In the presence of KBr/H2O 2, the anionic complexes 3, 6 and 8 catalyse the oxidative bromination of salicylaldehyde in water to 5-bromosalicylaldehyde in ca. 40% yields with ca. 87% selectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Maurya, Mannar R.,Agarwal, Shalu,Bader, Cerstin,Rehder, Dieter
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- Design and synthesis of novel Vitamin D-coumarin hybrids using microwave irradiation
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A series of novel vitamin D-coumarin hybrids were synthesised by esterification of the corresponding coumarin-3-carboxylic acids and vitamin D or vitamin D CD-ring alcohol in CH2Cl2 under microwave irradiation. They were obtained in higher yields (from 64-81% up to 79-87%) and shorter reaction time (from 3 h down to 15 min), compared with earlier conventional methodologies. The structures of all the target compounds were confirmed by 1H NMR, 13C NMR and HRMS. This provides an attractive and alternative method for the preparation of high-value vitamin D-coumarin hybrids.
- Zhang, Hengrui,Fang, Zhijie
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- Synthesis, characterization, reactivity, and catalytic studies of heterobimetallic vanadium(V) complexes containing hydrazone ligands
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Six heterobimetallic alkali metal dioxidovanadium(V) coordination polymer complexes {[M6{VO(μ-O)}2(μ-OH)4(μ4-slox/nph)].n DMF}∞ where M = Na, K, and Cs; n = 1 for (1), 0 for (2)-(6) of two dihydrazone ligands, disalicylaldehydeoxaloyldihydrazone (H4slox) and bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone (H4nph) are reported. All the complexes have been characterized by various physicochemical techniques such as elemental analyses, molar conductance, IR, NMR, UV–vis, and cyclic voltammetry. The IR, 1HNMR, and 13CNMR spectral data suggest that the dihydrazones are coordinated through phenolate/naphtholate oxygen, enolate oxygen, and azine nitrogen atoms to the metal centres. The structure of complex {[Na6{VO(μ-O)}2(μ-OH)4(μ4-slox)].DMF}∞ (1) is also determined by single-crystal X-ray data, which revealed that the H4slox coordinated via all possible dative sites to metal centres as tetrabasic octadentate ligand. The vanadium metal centres adopted distorted square-pyramidal coordination geometries, and the sodium atoms are also in five coordination atmospheres. The electronic spectra of the complexes showed LMCT bands in addition to intra-ligand π → π* and n → π* transitions. As evident from the cyclic voltammetry, the complexes showed two metal-centred electron transfer reactions {[(VVVV(slox)2?/VVVIV(slox)3?] and [(VVVIV(slox)3?/VVVIV(slox)4?]}, in addition to the ligand centred electron transfer reactions. Further, bovine serum albumin (BSA interaction studies of the complexes {[Na6{VO(μ-O)}2(μ-OH)4(μ4-slox)].DMF}∞ (1) and [Na6{VO(μ-O)}2(μ-OH)4(μ4-nph)]∞ (4) revealed strong binding affinity. Moreover, the catalytic studies of the complexes (1) and (4) were found to be effective for the oxidation of alcohols into their corresponding aldehydes and ketones and bromination of some organic substrates in the presence of H2O2 as an oxidizing agent.
- Borthakur, Rosmita,Dhanpat, Shobha A.,Kumar, Arvind,Kurbah, Sunshine D.,Lal, Ram A.,Syiemlieh, Ibanphylla
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supporting information
(2020/10/21)
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- Ni-NiO heterojunctions: a versatile nanocatalyst for regioselective halogenation and oxidative esterification of aromatics
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Herein, we report a facile method for the synthesis of Ni-NiO heterojunction nanoparticles, which we utilized for the nuclear halogenation reaction of phenol and substituted phenols usingN-bromosuccinimide (NBS). A remarkablepara-selectivity was achieved for the halogenated products under semi-aqueous conditions. Interestingly, blocking of thepara-position of phenol offeredortho-selective halogenation. In addition, the Ni-NiO nanoparticles catalyzed the oxidative esterification of carbonyl compounds with alcohol, diol or dithiol in the presence of a catalytic amount of NBS. It was observed that the aromatic carbonyls substituted with an electron-donating group favoured nuclear halogenation, whereas an electron-withdrawing group substitution in carbonyl compounds facilitated the oxidation reaction. In addition, the catalyst was magnetically separated and recycled 10 times. The tuned electronic structure at the Ni-NiO heterojunction controlled selectivity and activity as no suchpara-selectivity was observed with commercially available NiO or Ni nanoparticles.
- Bhardwaj, Nivedita,Goel, Bharat,Indra, Arindam,Jain, Shreyans K.,Singh, Ajit Kumar,Tripathi, Nancy
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p. 14177 - 14183
(2021/08/16)
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- Phosphine-catalyzed sequential (2+3)/(2+4) annulation of γ-vinyl allenoates: Access to the synthesis of chromeno[4,3-: B] pyrroles
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A phosphine-catalyzed cascade (2+3)/(2+4) cyclization reaction of γ-vinyl allenoates with aldimine esters has been developed to provide a series of chromeno[4,3-b]pyrrole derivatives that contain three contiguous stereogenic centers. The method gives a good yield, excellent chemoselectivity and diastereoselectivity under mild conditions.
- Huang, You,Li, Xiaohu
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supporting information
p. 9934 - 9937
(2021/10/12)
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- Oxidovanadium (V and IV) complexes incorporating coumarin based O^N^O ligand: Synthesis, structure and catalytic activities
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The tridentate ligand H2L1, [(E)-7-Hydroxy-8-[(2-hydroxy-phenylimino)-methyl]-4-methyl-chromen-2-one] has been used in the present work towards the synthesis of mononuclear oxidovanadium complexes. Three mononuclear complexes [VOL1(OMe)(MeOH)], 1; [VO(L1)(8-Hq)], 2 and [VO(L1)(1,10-phen)], 3 have been successfully synthesized with high yields by reacting [VO(acac)2] with H2L1 in 1:1 ratio in methanol under refluxing conditions where 8-hydroxyquinoline and 1,10-phenanthroline were used as co-ligands in the synthesis of complex 2 and 3. X-ray crystallographic studies reveal that in all the complexes synthesized in the present study, the ligand H2L1 binds as O^N^O coordinating ligand. The synthesized complexes were well characterized by using UV–Vis, IR, NMR and Mass spectral techniques. The physiochemical properties have been well interpreted by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The synthesized complexes were established to show some distinctive properties e.g. oxidative bromination of aromatic aldehyde with high conversion rate and enhanced selectivity as well as high TON and TOF. The above properties were all well matched and demonstrated by using UV–visible and fluorescence as well as quenching studies. Complex 1 reacts with 3,5-DTBC catalytically in presence of molecular oxygen to generate corresponding ortho-benzoquinone.
- Majumder, Mitali,Krishna Rajak, Kajal
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- Synthesis and characterization of dimeric μ-oxidovanadium complexes as the functional model of vanadium bromoperoxidase
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Two vanadium (IV) complexes [VIVO(Haeae-sal)(MeOH)]+ (1) and [VIVO(Haeae-hyap)(MeOH)]+ (2) were prepared by reacting [VO(acac)2] with ligands [H2aeae-sal] (I) and [H2aeae-hyap] (II) respectively. Condensation of 2-(2-aminoethylamino)ethanol with salicylaldehyde and 2-hydroxyacetophenone produces the ligands (I) and (II) respectively. Both vanadium complexes 1 and 2 are sensitive towards aerial oxygen in solution and rapidly convert into vanadium(V) dioxido species. Vanadium(V) dioxido species crystalizes as the dimeric form in the solid-state. Single-crystal XRD analysis suggests octahedral geometry around each vanadium center in the solid-state. To access the benefits of heterogeneous catalysis, vanadium(V) dioxido complexes were anchored into the polymeric chain of chloromethylated polystyrene. All the synthesized neat and supported vanadium complexes have been studied by a number of techniques to confirm their structural and functional properties. Bromoperoxidase activity of the synthesized vanadium(V) dioxido complexes 3 and 4 was examined by carrying out oxidative bromination of salicylaldehyde and oxidation of thioanisole. In the presence of hydrogen peroxide, 3 shows 94.4% conversion (TOF value of 2.739 × 102 h?1) and 4 exhibits 79.0% conversion (TOF value of 2.403 × 102 h?1) for the oxidative bromination of salicylaldehyde where 5-bromosalicylaldehyde appears as the major product. Catalysts 3 and 4 also efficiently catalyze the oxidation of thioanisole in the presence of hydrogen peroxide where sulfoxide is observed as the major product. Covalent attachment of neat catalysts 3 and 4 into the polymer chain enhances substrate conversion (%) and their catalytic efficiency increases many folds, both in the oxidative bromination and oxidation of thioether. Polymer supported catalysts 5 displayed 98.8% conversion with a TOF value of 1.127 × 104 h?1 whereas catalyst 6 showed 95.7% conversion with a TOF value of 4.675 × 103 h?1 for the oxidative bromination of salicylaldehyde. These TOF values are the highest among the supported vanadium catalysts available in the literature for the oxidative bromination of salicylaldehyde.
- Chaudhary, Nikita,Haldar, Chanchal,Kachhap, Payal,Kesharwani, Neha,Mahato, Arun Kumar,Maurya, Abhishek,Mishra, Vivek Kumar
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- Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
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4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
- AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
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p. 283 - 289
(2020/10/06)
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- Bioinspired catalysis and bromoperoxidase like activity of a multistimuli-responsive supramolecular metallogel: Supramolecular assembly triggered by pi-pi stacking and hydrogen bonding interactions
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We report the synthesis and characterization of a new self-assembled VO2-L metallogel. Gel formation was investigated by dissolving VO2-L in various solvents and it was found that water/methanol (1?:?9 (v/v) ratio) induces gel formation. The single crystal X-ray structure of the VO2-L metallogel exhibits C-H?O and N-H?O hydrogen bonding interactions and pi-pi stacking. The VO2-L xerogel obtained after removing the solvents was found to exhibit outstanding performance in catalysis. Bromoperoxidase-like activity of the VO2-L metallogel was also reported. The present catalytic studies are simple and proceed under mild conditions.
- Kurbah, Sunshine Dominic,Lal, Ram A.
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p. 5410 - 5418
(2020/04/17)
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- Stepwise mechanism for the bromination of arenes by a hypervalent iodine reagent
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A mild, metal-free bromination method of arenes has been developed using the combination of bis(trifluoroacetoxy)iodobencene and trimethylsilyl bromide. In situ-formed dibromo(phenyl)-λ3-iodane (PhIBr2) is proposed as the reactive intermediate. This methodology using PIFA/TMSBr has been applied with success to a great number of substrates (25 examples). The treatment of mono-substituted activated arenes led to para-brominated products (2u-z) in excellent 83-96% yields. Density functional theory calculations indicate a stepwise mechanism involving a double bromine addition followed by a type II dyotropic reaction with concomitant re-aromatization of the six-membered ring.
- Arrieta, Ana,Cossío, Fernando P.,Granados, Albert,Shafir, Alexandr,Vallribera, Adelina
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p. 2142 - 2150
(2020/03/11)
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- Synthesis and structure-activity relationship studies of hydrazide-hydrazones as inhibitors of laccase from trametes versicolor
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A series of hydrazide-hydrazones 1-3, the imine derivatives of hydrazides and aldehydes bearing benzene rings, were screened as inhibitors of laccase from Trametes versicolor. Laccase is a copper-containing enzyme which inhibition might prevent or reduce the activity of the plant pathogens that produce it in various biochemical processes. The kinetic and molecular modeling studies were performed and for selected compounds, the docking results were discussed. Seven 4-hydroxybenzhydrazide (4-HBAH) derivatives exhibited micromolar activity Ki = 24-674 μM with the predicted and desirable competitive type of inhibition. The structure-activity relationship (SAR) analysis revealed that a slim salicylic aldehyde framework had a pivotal role in stabilization of the molecules near the substrate docking site. Furthermore, the presence of phenyl and bulky tert-butyl substituents in position 3 in salicylic aldehyde fragment favored strong interaction with the substrate-binding pocket in laccase. Both 3- and 4-HBAH derivatives containing larger 3-tert-butyl-5-methyl- or 3,5-di-tert-butyl-2-hydroxy-benzylidene unit, did not bind to the active site of laccase and, interestingly, acted as non-competitive (Ki = 32.0 μM) or uncompetitive (Ki = 17.9 μM) inhibitors, respectively. From the easily available laccase inhibitors only sodium azide, harmful to environment and non-specific, was over 6 times more active than the above compounds.
- Giurg, Miros?aw,Maniak, Halina,Matyja, Konrad,Talma, Micha?,Trusek, Anna
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supporting information
(2020/03/23)
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- Peroxo–tungstate(VI) complexes: syntheses, characterization, reactivity, and DFT studies
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Abstract: Three new oxodiperoxo–tungsten(VI) complexes containing benzene core carboxylic acids, viz., benzoic acid, 2-chlorobenzoic acid, and 3-aminobenzoic acid as co-ligands have been synthesized from reaction of Na2WO6H4, 30% H2O2 and the corresponding co-ligands in aqueous medium. The compounds have been comprehensively characterized by elemental analyses, FT-IR, 1H NMR, UV–Vis spectral studies as well as by mass spectrometric and TGA analyses. The infrared spectra suggest occurrence of terminally bonded W=O as well as triangular bidentate peroxo groups (C2v) and monodentate carboxylate group bound to the WO4+ center. The mass spectra of the compounds are in good agreement with proposed molecular formulations. Thermogravimetric analyses indicate the existence of both lattice and coordinated water molecules in the complexes. Density functional theory (DFT) calculations were used to compute the frequencies of relevant vibrational modes, electronic properties and also to investigate structure of the compounds. Compound potassium(aquo)(2-chlorobenzoato)oxodiperoxo–tungstate(VI)dihydrate acts as an oxidant for bromide ion in aqueous phase bromination of chosen organic substrates to their corresponding bromo-organics. Graphical abstract: [Figure not available: see fulltext.]
- Das, Nandita,Chowdhury, Shubhamoy,Purkayastha, Ranendra N. Dutta
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p. 1255 - 1266
(2019/07/04)
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- Directed Structural Transformations of Coordination Polymers Supported Single-Site Cu(II) Catalysts to Control the Site Selectivity of C-H Halogenation
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A main difficulty in C-H bond functionalization is to undertake the catalyst control accurately where the reaction takes place. In this work, to achieve highly effective and regioselective single-site catalysts, a three-dimensional (3D) rhombus-like framework of {[Mn(Hidbt)DMF]·H2O}n (1) [H3idbt = 5,5′-(1H-imidazole-4,5-diyl)-bis(2H-tetrazole)] containing coordinated DMF molecules was constructed. For the dissolution-recrystallization structural transformation process, attractive structural transformations proceeded from 1 to a new crystalline species formulated as {[Mn3(idbt)2(H2O)2]·3H2O}n (2) with a 3D windowlike architecture, and then the Mn ions in 2 could be exchanged with Cu ions through cation exchange in a single-crystal to single-crystal fashion to produce the Cu-exchanged product {[Mn2Cu(idbt)2(H2O)2]·3H2O}n (2a), which had a windowlike framework like that of 2. Furthermore, 2 and 2a were used as heterogeneous catalysts for the regioselective C-H halogenation of phenols with N-halosuccinimides (NCS and NBS) to produce the site selective single monohalogenated products. It was found that the catalytic activity and site selectivity of 2a were much higher than those of 2, because the unique structural features of 2a with the uniformly dispersed CuII active centers served as a single-site catalyst with a site-isolated and well-defined platform to promote the C-H halogenation reaction in regiocontrol and guide an orientation that favored the para selectivity during the reaction process.
- Huang, Chao,Zhu, Kaifang,Zhang, Yingying,Shao, Zhichao,Wang, Dandan,Mi, Liwei,Hou, Hongwei
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supporting information
p. 12933 - 12942
(2019/10/11)
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- Synthesis, crystal structure and reactivity of homobimetallic vanadium(V) complexes derived from oxaloyldihydrazone ligands
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Treatment of V2O5 with dihydrazone ligands (H4L) (disalicylaldehydeoxaloyldihydrazone (H4L1 = H4slox), bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone (H4L2 = H4nph) and bis(5-bromosalicylaldehyde)oxaloyldihydrazone (H4L3 = H4sloxBr)) in methanol leads to the formation of homobimetallic vanadium(V) complexes of the composition [(CH3)2NH2]2[(VO2)2(L)]·nH2O, where n = 2 (1, 2) and n = 4 (3). The reaction of complexes 1–3 with H2O2 results in the formation of bis(monooxidoperoxidovanadate(V)) complexes[{VO(O2)}2(L)]2? and the reaction with HCl leads to the formation of oxidohydroxido species of the composition [(VO(OH)(L)]2?. The complexes show great potential for the oxidation of alcohols and the oxidative bromination of some organic substrates.
- Syiemlieh, Ibanphylla,Asthana, Mrityunjaya,Kurbah, Sunshine D.,Lal, Ram A.
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p. 202 - 216
(2019/06/19)
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- Reactivity and Catalytic Activity of Homobimetallic Vanadium(V) Complex Derived from Bis(5-chlorosalicylaldehyde)oxaloyldihydrazone Ligand
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Homobimetallic vanadium(V) complex of the composition [(CH3)2NH2+]2[(VO2)2(sloxCl)].4H2O was synthesized from the reaction of V2O5 with bis(5-chlorosalicylaldehyde)oxaloyldihydrazone ligand in a 1:1 molar ratio in methanol. The structure of the complex was established by X-ray crystallography. Reactivity of the complex with H2O2 leads to bis (monooxidoperoxidovanadate(V)) [{VO(O2)}2(sloxCl)]2? formation and with HCl, oxidohydroxido complex of composition [(VO (OH)(sloxCl)]2? was formed. Binding interaction of the complex was also investigated toward protein (BSA) and it was found to be 2.21 x 108?M?1. The catalytic activity of the complex in the oxidation of alcohols and oxidative bromination of some organic substrates was also studied, and it showed a great potent as a catalyst.
- Syiemlieh, Ibanphylla,Asthana, Mrityunjaya,Lal, Ram A.
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- Sequential Energy Transfer Catalysis: A Cascade Synthesis of Angularly-Fused Dihydrocoumarins
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An operationally simple one-pot protocol has been developed to enable the conversion of diversely substituted cinnamic acid derivatives into angularly-fused dihydrocoumarins (up to 94%). Inspired by coumarin biosynthesis, this reaction cascade harnesses photochemical E → Z alkene isomerization enabled by energy transfer catalysis using inexpensive thioxanthen-9-one (TX) under irradiation at 402 nm. Subsequent lactonization generates the heterocyclic core prior to a second photosensitization event to induce a [2 + 2] cycloaddition, again mediated by TX. The tetracyclic products are generated efficiently, and proof of the structure was established by X-ray crystallography. Mechanistic investigations, including structural probes and NMR reaction monitoring, support the postulated order of events. The study underscores the synthetic value of inexpensive small-molecule organic photocatalysts in the generation of structural complexity via sequential ?€-bond activation.
- Nevesely, Tomá?,Daniliuc, Constantin G.,Gilmour, Ryan
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supporting information
p. 9724 - 9728
(2019/11/29)
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- A phenol compound high regioselective bromination method
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The invention discloses a phenol compound high regioselective bromination of the method, the method to trimethyl silane as brominating agent, in order to aryl sulfoxide as activator, with the phenol compound in the 0 - 50 °C lower, in a solvent, the reaction is stirred under an atmosphere of nitrogen at 1 - 12 hours, to realize the phenol compound high regioselective bromination, filtered, extraction columns chromatography separation to obtain the bromo phenol compound. This invention adopts the aryl sulfoxide as activator, sulfoxide substituted Kiev, on the one hand so that the phenol compound bromo the higher selectivity of the reaction region, and when the phenol compound hydroxy alignment not substituted basetime, regional selective para - bromo product, when the phenol compound hydroxy position there is substituted basetime, selective ortho - bromo product obtained; on the other hand if it through the filter, the extraction can be realized at the same time the isolation and purification of the recycling of the by-product, compared with column chromatography, reduces the separation and purification cost.
- -
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Paragraph 0049; 0050; 0051
(2019/06/05)
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- Design, synthesis and preliminary biological evaluation of benzylsulfone coumarin derivatives as anti-cancer agents
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In this work, a series of benzylsulfone coumarin derivatives 5a-5o were synthesized and characterized. Kinase inhibitory activity assay indicated that most of the compounds showed considerable activity against PI3K. Anti-tumor activity studies of the active compounds were also carried out in vitro on the Hela, HepG2, H1299, HCT-116, and MCF-7 tumor cell lines by MTS assay. The structure-activity relationships (SARs) of these compounds were analyzed in detail. Compound 5h exhibited the most potent activities against the mentioned cell lines with IC50 values ranging from 18.12 to 32.60 μM, followed by 5m with IC50 values of 29.30-42.14 μM. Furthermore, 5h and 5m clearly retarded the migration of Hela cells in vitro. Next, an in silico molecular docking study was conducted to evaluate the binding models of 5h and 5m towards PI3Kαand PI3Kβ. Collectively, the above findings suggested that compounds 5h and 5m might be promising PI3K inhibitors deserving further investigation for cancer treatment.
- Wang, Tao,Peng, Tao,We, Xiaoxue,Wang, Gang,Sun, Yunbo,Liu, Shuchen,Zhang, Shouguo,Wang, Lin
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supporting information
(2019/11/20)
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- Mild and Regioselective Bromination of Phenols with TMSBr
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In this work, an unexpected promoting effect of by-product thioether was observed, leading to a mild and regioselective bromination of phenols with TMSBr. This method can tolerate a series of functional groups such as the reactive methoxyl, amide, fluoro, chloro, bromo, aldehyde, ketone and ester groups, and has the potential to recycle the by-product thioether and isolate the desired product under column chromatography-free conditions. Mechanism studies revealed that O–H···S hydrogen bond may be formed between phenol and by-product thioether. Possibly owing to the steric hindrance effect from by-product thioether, the electrophilic bromination at para-position of phenols is much favorable.
- Ma, Xiantao,Yu, Jing,Jiang, Mengyuan,Wang, Mengyu,Tang, Lin,Wei, Mengmeng,Zhou, Qiuju
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supporting information
p. 4593 - 4596
(2019/07/05)
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- Two dinuclear oxidovanadium(V) complexes of N2O2 donor amine-bis(phenolate) ligands with bromo-peroxidase activities: Kinetic, catalytic and computational studies
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Two dinuclear oxidovanadium(V) complexes [LiVVO(μ2-O)VVO(Li)] (i = 1, H2L1, complex 1 and i = 2 for H2L2, complex 2) of two ONNO donor amine-bis(phenolate) ligands have been synthesized and characterized by X-ray diffraction studies which exhibited distorted octahedral geometry around each V center. In MeCN the complexes exist as dimers as indicated by HRMS studies, however, in the presence of 2 or more equivalents of H+ the dimers turned into monomers, ([LiVV = O]+ which exists in equilibrium with ([LiVV = OH]2+ and evidenced from the shift in λmax from 685 nm to 765 nm for complex 1 and 600 to 765 nm for complex 2. The complexes 1 and 2 efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo-salicylaldehyde as the major product with TONs 405 and 450, respectively in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide ion oxidation reaction indicates a mechanism which is first order in peroxidovanadium complex and bromide ion and limiting first-order on [H+]. The evaluated kBr and kH values are (8.82 ± 0.35) and (65.0 ± 2.23) M?1 s?1 for complex 1 and (6.74 ± 0.19) and (61.87 ± 2.27) M?1 s?1 for complex 2, respectively. The Ka of protonated species ([LiVV = OH]2+ are: Ka = (4.3 ± 0.40) × 10?3 (pKa = 2.37) and (4.7 ± 0.50) × 10?3 (pKa = 2.33) for complex 1 and 2 respectively. On the basis of the chemistry displayed by these model compounds, a mechanism of bromide oxidation and a tentative catalytic cycle have been framed which might be relevant to vanadium haloperoxidase enzymes and supported by DFT calculations.
- Debnath, Mainak,Dolai, Malay,Pal, Kaberi,Dutta, Arpan,Lee, Hon Man,Ali, Mahammad
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p. 149 - 158
(2018/05/28)
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- Polymer-anchored [Fe(III)Azo] complex: An efficient reusable catalyst for oxidative bromination and multi-components reaction for the synthesis of spiropiperidine derivatives
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A heterogeneous catalyst was prepared by attaching Fe(III) into organically modified chloromethylated polytstyrene and characterized by AAS, IR, PXRD, TG-DTA, UV–Vis, and SEM studies. In presence of H2O2 and KBr as bromine source, the catalyst showed remarkably high conversion with para-selectivity towards the oxidative bromination reaction in acetic acid medium. The catalyst was also very active and highly efficient for the production of spiropiperidine derivatives through multi-component reaction in isopropyl alcohol at room temperature. The catalyst was not leached during the catalytic reactions, moreover, after five cycles the catalytic activity and selectivity of the catalyst were not decreased very significantly.
- Khatun, Resmin,Biswas, Surajit,Ghosh, Swarbhanu,Islam, Sk. Manirul
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- Dioxidomolybdenum(VI) complexes bearing sterically constrained aroylazine ligands: Synthesis, structural investigation and catalytic evaluation
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Seven new dioxidomolybdenum(VI) complexes [MoO2L1(X)].X (1) and [MoO2L2–7(X)] (2–7) [Where X = EtOH in case of 1 and 5 and X = DMSO in case of 2–4 and 6, 7] of aroylazines containing a bulky 3-hydroxy-2-naphthoic substituent, were isolated and structurally characterized. The aroylazine ligands H2L1–7 were derived from the condensation of 3-hydroxy-2-naphthoic acid hydrazide with several substituted aromatic aldehydes/ketones. All the synthesized ligands and metal complexes were successfully characterized by elemental analysis, IR, UV–Vis and NMR spectroscopy. X-ray structures of 1–6 revealed that the ligands coordinate to the metal center as a dibasic tridentate ligand. Cyclic voltammetry of the complexes shows two irreversible reductive responses within the potential window ?0.50 to ?1.36 V, due to MoVI/MoV and MoV/MoIV processes. The synthesized complexes 1–7 were used as catalysts for the oxidation of benzoin, and for the oxidative bromination of salicylaldehyde, as a functional mimic of haloperoxidase. It was found that the percentage of conversion increased significantly in the presence of catalysts 1–7 which contained bulky substituents, and showed high percentage of conversion (>90%) with high turnover frequency (>1100 h?1) than previously reported catalysts. Benzil, benzoic acid and benzaldehyde-dimethylacetal were formed selectively for the oxidation of benzoin. Formation of 5-bromosalicylaldehyde and 3,5-dibromosalicylaldehyde took place during the oxidative bromination of salicylaldehyde in presence of H2O2 as an oxidant and therefore 1–7 act as functional models of vanadium dependent haloperoxidases.
- Majumder, Sudarshana,Pasayat, Sagarika,Roy, Satabdi,Dash, Subhashree P.,Dhaka, Sarita,Maurya, Mannar R.,Reichelt, Martin,Reuter, Hans,Brzezinski, Krzysztof,Dinda, Rupam
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p. 366 - 378
(2017/10/06)
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- Co-immobilization of Laccase and TEMPO in the Compartments of Mesoporous Silica for a Green and One-Pot Cascade Synthesis of Coumarins by Knoevenagel Condensation
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Co-immobilization of bio- and chemocatalysts produces sustainable, recyclable hybrid systems that open new horizons for green cascade approaches in organic synthesis. Here, the co-immobilization of laccase and 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) in mesoporous silica was used for the one-pot aqueous synthesis of 30 coumarin-3-carboxylate derivatives under mild conditions through the condensation of in situ oxidized 2-hydroxybenzyl alcohols and malonate derivatives. A maximum yield was obtained after incubating at pH 6.0 and 45 °C for 24 h. An efficient organic synthesis was catalyzed by the hybrid catalyst in 10 % organic solvent. More than 95 % of the initial activity of the enzyme was preserved after 10 cycles, and no significant catalyst deactivation occurred after 10 runs. This new system efficiently catalyzed the in situ aerobic oxidation of salicyl alcohols, followed by Knoevenagel condensation, which confirmed the possibility of producing efficient hybrid catalysts by co-immobilization of catalytic species in mesoporous materials.
- Mogharabi-Manzari, Mehdi,Amini, Mohsen,Abdollahi, Mohammad,Khoobi, Mehdi,Bagherzadeh, Ghodsieh,Faramarzi, Mohammad Ali
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p. 1542 - 1546
(2018/02/28)
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- New dioxido-vanadium(V) complexes containing hydrazone ligands: Syntheses, crystal structure and their catalytic application toward C–H bond functionalization
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New dioxido-vanadium(V) complexes derived from hydrazone ligands have been synthesized in good yield. The complexes were characterized by elemental analysis, IR, UV–Visible and 1H NMR spectroscopies. The structure of both the complexes was established by Single Crystal X-ray crystallography. Complex 1 crystallized in monoclinic P21/n space group, with cell parameters a = 8.3725(5) ? b = 15.0475(17) ? c = 32.227(3) ? α = 90° β = 91.846(5)o, γ = 90°. Complex 2 crystallized in triclinic P-1 space group, a = 8.1871(7) ? b = 11.2605(17) ? c = 11.4031(18) ? α = 105.961(14)° β = 110.528(12)o and γ = 96.387(10)o. Both the complexes act as efficient catalyst which can catalyse the C–H bond functionalization reaction.
- Kurbah, Sunshine D.,Asthana,Syiemlieh,Lywait, Alzelia A.,Longchar,Lal
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- Ultrasonically assisted halogenation of aromatic compounds using isoquinolinium bound hypervalent chromium and tetrabutylammonium halides in PEG-600 solutions under acid free and solvent-free conditions
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Isoquinolinium bound Cr(VI) reagents like isoquinolinium dichromate (IQDC) and isoquinolinium chlorochromate (IQCC) have been successfully accomplished as efficient reagents for oxidative halogenation of aromatic compounds using tetrabutylammonium halide (TBAX) as halogenating agents in aqueous polyethylene glycol (PEG-600) under acid free conditions. Tetrabutylammonium bromide (TBAB) has been used for bromination and tetrabutylammonium iodide (TBAI) for iodination. The halogenation reactions that occurred smoothly in 2 to 7 h under conventional conditions are accelerated magnificently under sonication with few minutes (25 to 70 min) of reaction time and fairly good yields. The reactions occurred at moderate temperature under mild and environmentally safe conditions with simple work up.
- Sambashiva Rao,Ramesh, Kola,Rajanna,Chakrvarthi
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p. 1892 - 1896
(2018/07/10)
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- Cytotoxicity of new pyridazin-3(2H)-one derivatives orchestrating oxidative stress in human triple-negative breast cancer (MDA-MB-468)
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Triple-negative breast cancer (TNBC) is a complex and aggressive subtype of breast cancer characterized by high morbidity and mortality. In the absence of targeted therapy, only chemotherapy is available in this case of cancer. The current study investigated the antitumor effect of new pyridazin-3(2H)-one derivatives on the human TNBC cell line, MD-MB-468. The in vitro cytotoxic activities were investigated using the tetrazolium-based MTT assay. Lipid peroxidation, H2O2 content, and the specific activities of antioxidant enzymes were also determined. Two molecules, 6f and 7h, were found to be selectively highly active against tumor cells with IC50 values of 3.12 and 4.9 μM, respectively. Furthermore, cells exposed to 6f showed a significant increase in H2O2 and lipid peroxidation levels, accompanied by a decrease in the enzyme activities of glutathione reductase (GR) and thioredoxin reductase (TrxR). The cytotoxicity of the compound 6f may improve the therapeutic efficacy of the current treatment for TNBC via the inhibition of GR and TrxR activities.
- Bouchmaa, Najat,Ben Mrid, Reda,Boukharsa, Youness,Nhiri, Mohamed,Ait Mouse, Hassan,Taoufik, Jamal,Ansar, M'hammed,Zyad, Abdelmajid
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- Enantioselective Construction of Tetrahydroquinazoline Motifs via Palladium-Catalyzed [4 + 2] Cycloaddition of Vinyl Benzoxazinones with Sulfamate-Derived Cyclic Imines
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A palladium-catalyzed enantioselective [4 + 2] cycloaddition reaction of vinyl benzoxazinones with sulfamate-derived cyclic imines is described, affording the tetrahydroquinazolines bearing several functional rings in high yields (up to 99% yield) with good to excellent diastereoselectivities and excellent enantioselectivities (up to 96% ee). This reaction represents the first Pd-catalyzed asymmetric decarboxylative cycloaddition of vinyl benzoxazinones with imines.
- Wang, Chang,Li, Yan,Wu, Yang,Wang, Qijun,Shi, Wangyu,Yuan, Chunhao,Zhou, Leijie,Xiao, Yumei,Guo, Hongchao
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supporting information
p. 2880 - 2883
(2018/05/29)
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- Synthesis, characterization and cytotoxicity of platinum(II) complexes containing reduced amino acid ester Schiff bases
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Nine platinum(II) complexes containing reduced amino acid ester Schiff bases were synthesized and characterized using spectroscopy (1H NMR, 13C NMR, infrared), elemental analysis and molar conductivity. The interaction of these complexes with salmon sperm DNA was investigated by means of ultraviolet and circular dichroism spectroscopies. The potential antitumor activity of all compounds was tested in vitro on HeLa and A549 tumor cell lines. Almost all the complexes exhibited better cytotoxic activity than cisplatin against these cell lines.
- Yan, Qin-Qin,Yuan, Zhen,Liu, Guo-Jun,Lv, Zheng-Hua,Fu, Bin,Du, Jian-Long,Li, Li-Jun
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- Synthesis characterization and cytotoxicity studies of platinum(II) complexes with reduced amino pyridine schiff base and its derivatives as ligands
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A series of reduced amino pyridine Schiff base platinum(II) complexes were prepared as potential anticancer drugs, and characterized by NMR, IR spectroscopy, elemental analysis, and molar conductivity. UV and CD results showed the binding mode between these compounds and salmon sperm DNA may be intercalation. The cytotoxicity of these complexes was validated against A549, Hela, and MCF-7 cell lines by MTT assay. Some complexes exhibited better cytotoxic activity than cisplatin against Hela and MCF-7 cell lines.
- Li, Li-Jun,Yan, Qin-Qin,Liu, Guo-Jun,Yuan, Zhen,Lv, Zhen-Hua,Fu, Bin,Han, Yan-Jun,Du, Jian-Long
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p. 1081 - 1089
(2017/05/29)
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- Syntheses, Structural Characterization, Reactivity, and Theoretical Studies on Some Heteroligand Oxoperoxotungstate(VI)
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White microcrystalline diamagnetic oxoperoxotungstate(VI) complexes K[WO(O2)2F]·H2O, K2[WO(O2)2(CO3)]·H2O, [WO(O2)(SO4)(H2O)2] have been synthesized from reaction of Na2WO4·2H2O with aqueous HF, solid KHCO3, aqueous H2SO4 (W:F? 1:3; W: CO3 2 ? 1:1; and W: SO4 2 ? 1:3), and an excess of 30% H2O2 at pH 7.5–8. Precipitation was completed by the addition of precooled acetone. The occurrence of terminal W?O and triangular bidentate O2 2 ?(C 2 v) in the synthesized compounds was ascertained from IR spectra. The IR spectra also suggested that the F? and SO4 2 ? ions in K[WO(O2)2F]·H2O and [WO(O2)(SO4)(H2O)2] were bonded to the WO +4 center in monodentate manner, while CO3 2 ? ion in K2[WO(O2)2(CO3)]·H2O binds the metal center in bidentate chelating fashion. The complex [WO(O2)(SO4)(H2O)2] is stable upto 110°C. The water molecule in [WO(O2)(SO4)(H2O)2] is coordinated to the WO +4 center, whereas it occurs as water of crystallization in the corresponding peroxo(fluoro) and peroxo(carbonato) compounds. Mass spectra of the compounds are in good agreement with the molecular formulae of the complexes. K2[WO(O2)2(CO3)]·H2O acts as an oxidant for bromide in the aqueous-phase bromination of organic substrates to the corresponding bromo-organics, and the complex also oxidizes Hantzsch-1,4-dihydropyridine to the corresponding pyridine derivative in excellent yield at room temperature. Density functional theory computation was carried out to compute the frequencies of relevant vibrational modes and electronic properties, and the results are in agreement with the experimentally obtained data.
- Das, Nandita,Chowdhury, Shubhamoy,Dutta Purkayastha, Ranendra N.
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- Complexes of cis-dioxomolybdenum(VI) with a chiral tetradentate tripodal-like ligand system: Syntheses, structures and catalytic activities
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Racemic complexes with the general formula cis-[MoO2(bzacLn)] (1–4) (H2bzacLn?=?2-((4/5-R-2-hydroxyphenylamino)(pyridin-2-yl)methyl)-1-phenylbutane-1,3-dione, where n?=?1–4 for R?=?H, 5-Me, 5-Cl and 4-Me, respectively and 2Hs represent the dissociable phenolic proton and the active tertiary CH proton) have been synthesized in 75–82% yields by reacting [MoO2(bzac)2] (Hbzac?=?benzoylacetone) with the potentially N2O-donor 5,5-membered fused chelate rings forming Schiff bases 4/5-R-2-(2-pyridylaldimine)phenols (HLn; n?=?1–4 for R?=?H, 4-Me, 4-Cl and 5-Me, respectively) in hot methanol. The chiral ligand system (bzacLn)2?in 1–4 is formed via metal assisted Mannich-type addition of benzoylacetonate methine to the azomethine fragment of HLn. All four complexes have been characterized by elemental (CHN) analysis, solution conductivity, magnetic susceptibility, spectroscopic (IR, UV–Vis and NMR) and electrochemical measurements. The molecular structures of 1–3 have been established by single crystal X-ray crystallography. In each complex, the chiral (bzacLn)2?acts as a tetradentate, N2O2-donor, tripodal-like ligand system and along with the two mutually cis oxo groups forms a distorted octahedral N2O4coordination environment around the molybdenum(VI) center. All four complexes are diamagnetic and non-electrolytic. The infrared spectra are generally consistent with the structural formulas of 1–4. The electronic spectra of 1–4 in dimethylformamide display two strong absorption bands in the range 245–300?nm. The cyclic voltammograms of 1–4 in dimethylformamide exhibit a metal centered one-electron reduction response within ?0.64 to ?0.74?V. All these complexes (1–4) and the analogous cis-[MoO2(acacL1–4)] (5–8) synthesized from [MoO2(acac)2] (Hacac?=?acetylacetone) and HL1–4have been evaluated for their bromoperoxidase activities.
- Ghosh, Sabari,Kurapati, Sathish Kumar,Pal, Samudranil
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- Dual roles of sulfonyl hydrazides in the catalyst-free sulfonylation of unsaturated benzylic alcohols in water
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An atom-economical sulfonylation of unsaturated benzylic alcohols in water is described. In this transformation, dual roles of sulfonyl hydrazides serving as both a sulfonyl source and a reductant have been demonstrated, which enabled a facile and green method to synthesize alkyl sulfones from unsaturated benzylic alcohols. Moreover, this approach provides a practical access to deuterated alkanes from the corresponding alkenes by employing the combination of sulfonyl hydrazides and the solvent D2O.
- Xu, Kun,Li, Lijun,Yan, Wen,Wu, Yuanyuan,Wang, Zhiqiang,Zhang, Sheng
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supporting information
p. 4494 - 4497
(2017/10/13)
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- Phosphine-Catalyzed [4 + 2] Annulation of Allenoate with Sulfamate-Derived Cyclic Imines: A Reaction Mode Involving γ′-Carbon of α-Substituted Allenoate
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A phosphine-catalyzed [4 + 2] cycloaddition of cyclic α-substituted allenoates with sulfamate-derived cyclic imines has been reported. Using dibenzylphenylphosphine as the nucleophilic catalyst, the reaction worked efficiently to yield various fused multicyclic heterocyclic compounds in high yields with excellent diastereoselectivities. It undergoes a new reaction mode involving γ′-carbon of α-substituted allenoate.
- Mao, Biming,Shi, Wangyu,Liao, Jianning,Liu, Honglei,Zhang, Cheng,Guo, Hongchao
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supporting information
p. 6340 - 6343
(2017/12/08)
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- Pd-Catalyzed Ortho C-H Hydroxylation of Benzaldehydes Using a Transient Directing Group
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The direct Pd-catalyzed ortho C-H hydroxylation of benzaldehydes was achieved using 4-chloroanthranilic acid as the transient directing group, 1-fluoro-2,4,6-trimethylpyridnium triflate as the bystanding oxidant, and p-toluenesulfonic acid as the putative oxygen nucleophile. The unusual C-H chlorination and polyfluoroalkoxylation reactions signaled the importance of external nucleophiles to the outcome of Pd(IV) reductive eliminations.
- Chen, Xiao-Yang,Ozturk, Seyma,Sorensen, Erik J.
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supporting information
p. 6280 - 6283
(2017/12/08)
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- Cis-Dioxomolybdenum(VI) complexes with unsymmetric linear tetradentate ligands: Syntheses, structures and bromoperoxidase activities
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Reactions of [MoO2(acetylacetonate)2], 2-((2-(2-hydroxyethylamino)ethylamino)methyl)-4-R-phenols (H2Ln, n = 1-5 for R = H, Me, OMe, Cl and Br, respectively) and KOH in 1:1:2 mole ratio in methanol afford a series of complexes having the general formula cis-[MoO2(Ln)] (1, 2, 3, 4, 5) in 81-86% yields. The complexes have been characterized using elemental analysis, spectroscopy (infrared, UV-visible, and 1H NMR, 13C NMR and 13C-DEPT NMR) and electrochemical measurements. The molecular structures of 1, 2, 3, 4 have been determined using single-crystal X-ray crystallography. In each of 1, 2, 3, 4, the ONNO-donor 6,5,5-membered fused chelate rings forming (Ln)2- and the two mutually cis oxo groups assemble a distorted octahedral N2O4 coordination sphere around the metal centre. In the crystal lattice, each of 1, 2, 3, 4 forms a one-dimensional infinite chain structure via intermolecular N-H...O hydrogen bonding interactions. In cyclic voltammograms, the diamagnetic complexes display an irreversible metal-centred reduction in the potential range -0.73 to -0.88 V (vs Ag/AgCl). The physicochemical data are consistent with a very similar gross molecular structure for all of 1, 2, 3, 4, 5. All the complexes exhibit decent bromoperoxidase activities and are also able to effectively catalyse benzoin and methyl(phenyl)sulfide oxidation reactions.
- Kurapati, Sathish Kumar,Pal, Samudranil
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p. 116 - 124
(2016/02/18)
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- Isoquinolinium Dichromate and Chlorochromate as Efficient Catalysts for Oxidative Halogenation of Aromatic Compounds under Acid-Free Conditions
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Isoquinolinium dichromate and isoquinolinium chlorochromate were found as efficient catalysts to trigger oxidative bromination and iodination of aromatic hydrocarbons with KBr/KI and KHSO4 under acid-free conditions. Reaction times reduced highly significantly under sonication, followed by corresponding mono bromo derivatives in very good yield with high regioselectivity.
- Rao, A. Sambashiva,Rajanna,Reddy, K. Rajendar,Kulkarni, Subhash
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p. 832 - 837
(2016/02/12)
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- On the bromination of aromatics, alkenes and alkynes using alkylammonium bromide: Towards the mimic of bromoperoxidases reactivity
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This article describes an efficient method of bromination of organic substrates including aromatics, alkenes and alkynes with NH4VO3as a catalyst and H2O2as an oxidant agent using a non-toxic and easy-to-handle source of bromine, tetrabutylammonium bromide. The process was developed under mild reaction conditions and is an innovation from reported methods in aspects such as: i) short reaction times, ii) the ability to work at room temperature, iii) regioselectivity and good yields.
- Mendoza, Fabian,Ruíz-Guerrero, Rosario,Hernández-Fuentes, Carlos,Molina, Paulina,Norzagaray-Campos, Mariano,Reguera, Edilso
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supporting information
p. 5644 - 5648
(2016/11/28)
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- Complexes of cis-dioxomolybdenum(VI) with unsymmetrical tripodal NO3-donor ligands: Synthesis, characterization and catalytic applications
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A series of cis-dioxomolybdenum(VI) complexes of general formula cis-[MoO2(HLn)] (1-4) have been synthesized in 80-85% yields by reacting equimolar amounts of [MoO2(acac)2] (acac- = acetylacetonate) with 2,2′-(2-hydroxy-3,5-R1,R2-benzylazanediyl)diethanols (H3Ln, n = 1-4) in methanol. Characterization of the complexes has been performed by elemental analysis, spectroscopic (IR, UV-Vis, 1H and 13C NMR) and electrochemical measurements. The molecular structures of all four complexes have been determined by single-crystal X-ray diffraction studies. In each of these analogous complexes, the metal centre is in a distorted octahedral NO5 coordination sphere assembled by the single edge shared 5,5,6-membered chelate rings forming NO3-donor (HLn)2- and two cis oriented oxo groups. Crystal structures of the complexes reveal formation of discrete centrosymmetric dimeric species via a pair of reciprocal intermolecular O-HO hydrogen bonding interactions. Spectroscopic data of all the complexes are consistent with their molecular structures. In the cyclic voltammograms, the redox-active complexes display a quasi-reversible to irreversible metal centred reduction with the cathodic peak potential in the range -0.92 to -1.12 V (versus Ag/AgCl). All the complexes have been evaluated for their catalytic activities in oxidative bromination reactions of styrene and salicylaldehyde and in benzoin oxidation reaction.
- Kurapati, Sathish Kumar,Maloth, Swamy,Pal, Samudranil
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- Synthesis of para-aryl-substituted salicyldialdehydes
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para-Substituted salicyldialdehydes are versatile molecular building blocks for porous organic cages, fluorescent dyes, spirobenzopyrans, homooxacalixarenes, dinuclear metal complexes, macrocycles, and cryptands. To date, no procedures for the synthesis of para-aryl-substituted salicyldialdehydes have been reported, which would broaden the scope of the above-mentioned topics, especially in the field of sensors and dyes, because the aromatic π systems can be enlarged and absorption or fluorescent events can be fine-tuned by various substituents. Herein, two synthetic routes to para-aryl-substituted salicyldialdehydes with both electron-withdrawing and -donating aromatic units are reported.
- Reinhard, Dennis,Sch?ttner, Ludger,Brosius, Victor,Rominger, Frank,Mastalerz, Michael
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p. 3274 - 3285
(2015/05/20)
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- A new oxidovanadium(IV) complex containing an O, N-bidentate Schiff base ligand: Synthesis, characterization, crystal structure determination, thermal study and catalytic activity for an oxidative bromination reaction
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A new oxidovanadium(IV) schiff base complex (1) containing an ethyl bromide pendant group was synthesized by the reaction of the related bidentate O, N-Schiff base ligand and VO(acac)2 in a 2:1 ratio in methanol, under reflux conditions. The Schiff base ligand and its vanadyl Schiff base complex were characterized by 1H NMR and FT-IR spectra, and CHN analysis. The crystal structure of 1 was also determined by single crystal X-ray analysis. The vanadium center in this structure has a distorted tetragonal pyramidal N2O3 coordination sphere. The Schiff base ligand HL acts as a bidentate ligand by coordinating via the nitrogen atom of the imine group and the oxygen atom of the phenolic group, thereby forming a six-membered chelating ring. There are some non-classical inter- and intra-molecular hydrogen bonds of the type C-Ha?O and C-Ha?Br in 1. The catalytic activity of 1 was studied for the oxidative bromination of 2-nitrophenol as a model substrate. Different reaction parameters were studied in this reaction and the oxidative bromination of some organic compounds by a catalytic amount of 1 showed that it was an effective and selective catalyst under optimal conditions. Thermogravimeric analysis of 1 showed that it decomposed in two stages. In addition, complex 1 thermally decomposed in air at 660 C and the XRD pattern of the obtained solid showed the formation of V2O5 nanoparticles with an average size of 57 nm.
- Grivani, Gholamhossein,Tahmasebi, Vida,Khalaji, Aliakbar Dehno
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p. 144 - 150
(2013/12/04)
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- Synthesis, characterization, crystal structure, catalytic activity in oxidative bromination, and thermal study of a new oxidovanadium Schiff base complex containing O, N-bidentate Schiff base ligand
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A new oxidovanadium(IV) Schiff base complex, VOL2 (1), HL = 2-{(E)-[2-(bromoethyl)imino]methyl}-6-methoxy phenol, containing ethyl bromide pendant group was synthesized by direct reaction of HL and VO(acac)2 in the ratio of 2: 1 in methanol at reflux. The Schiff base ligand and its vanadyl complex were characterized by FT-IR spectra and CHN analysis. Additionally, the Schiff base ligand has been characterized by 1H NMR spectroscopy. The crystal structure of 1 was also determined by single-crystal X-ray analysis, showing the distorted square-pyramidal N2O3 coordination around vanadium(IV). The catalytic activity of 1 was studied in the oxidative bromination of 2-nitrophenol as a model substrate, and different reaction parameters were investigated. The oxidative bromination of some organic compounds in the presence of 1 in optimal conditions showed that it was an effective and selective catalyst in those optimal conditions. Thermogravimetric analysis of 1 showed that it decomposed in two stages. 1 was thermally decomposed in air at 660 °C, and the XRD pattern of the obtained solid showed the formation of the V2O5 nanoparticles with average size of 34 nm.
- Grivani, Gholamhossein,Tahmasebi, Vida,Khalaji, Aliakbar Dehno,Eigner, Václav,Du?ek, Michal
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p. 3664 - 3677
(2015/10/19)
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- Synthesis, characterization, X-ray crystal structure, DFT calculations, and catalytic properties of a dioxidovanadium(V) complex derived from oxamohydrazide and pyridoxal: A model complex of vanadate-dependent bromoperoxidase
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A vanadium(V) complex with the formula [Et3NH][VVO2(sox-pydx)] with a new tridentate ligand 2-[2-[[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl]methylene]hydrazinyl]-2-oxoacetamide (soxH-pydxH), obtained by condensation of oxamohydrazide and pyridoxal (one of the forms of vitamin B6), has been synthesized. The compound was characterized by various analytical and spectroscopic methods, and its structure was determined by single-crystal X-ray diffraction technique. Density functional theory (DFT) and time-dependent DFT calculations were used to understand the electronic structure of the complex and nature of the electronic transitions observed in UV-vis spectra. In the complex, vanadium(V) is found to be pentacoordinated with two oxido ligands and a bianionic tridentate ONO-donor ligand. The vanadium center has square-pyramidal geometry with an axial oxido ligand, and the equatorial positions are occupied by another oxido ligand and a phenolato oxygen, an imine nitrogen, and a deprotonated amide oxygen of the hydrazone ligand. A DFT-optimized structure of the complex shows very similar metrical parameters as determined by X-ray crystallography. The O4N coordination environment of vanadium and the hydrogen-bonding abilities of the pendant amide moiety have a strong resemblance with the vanadium center in bromoperoxidase enzyme. Bromination experiments using H2O2 as the oxidizing agent, with model substrate phenol red, and the vanadium complex as a catalyst show a remarkably high value of kcat equal to 26340 h-1. The vanadium compound also efficiently catalyzes bromination of phenol and salicylaldehyde as well as oxidation of benzene to phenol by H2O2.
- Das, Chandrima,Adak, Piyali,Mondal, Satyajit,Sekiya, Ryo,Kuroda, Reiko,Gorelsky, Serge I.,Chattopadhyay, Shyamal Kumar
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p. 11426 - 11437
(2015/02/18)
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- Synthesis, characterization and cytotoxicity studies of platinum(II) complexes with reduced amino acid ester Schiff-bases as ligands
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A series of platinum(II) complexes with reduced amino acid esters Schiff-bases as ligands were prepared as potential anticancer agents and characterized by NMR, IR spectroscopy, elemental analysis and molar conductivity. These compounds were tested for their stability and DNA interaction with salmon sperm DNA by ultraviolet spectrum. The cytotoxicities of these complexes were validated against HL-60, BGC-823, Hela, and HepG2 cell lines by the MTT test. The complexes 5e and 5f exhibited better cytotoxic activity than cisplatin against HepG2 and BGC-823 cell lines, respectively.
- Li, Li-Jun,Fu, Bin,Qiao, Yu,Wang, Cheng,Huang, Ying-Ying,Liu, Chuan-Chuan,Tian, Chao,Du, Jian-Long
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p. 135 - 140
(2014/06/23)
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- Aerobic oxidation and oxidative bromination in aqueous medium using polymer anchored oxovanadium complex
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Polymer anchored oxovanadium catalyst was synthesized and characterized. Its catalytic activity was evaluated for the oxidation of various primary and secondary alcohols with molecular oxygen under mild reaction conditions. This catalyst was also effective for the oxidative bromination reaction of organic substrates with 90-100% selectivity of mono substituted products with H 2O2/KBr at room temperature. The above reactions require low temperature, short time period and most importantly all the above reactions occur in aqueous medium. The developed catalyst can be facilely recovered and reused six times without significant decrease in activity and selectivity. 2014 Elsevier B.V. All rights reserved.
- Islam, Sk. Manirul,Molla, Rostam Ali,Roy, Anupam Singha,Ghosh, Kajari,Salam, Noor,Iqubal, Md. Asif,Tuhina
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p. 169 - 178
(2014/05/06)
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