• Archana

      Articles written in Journal of Chemical Sciences

    • Mössbauer and other spectral studies of Fe(III) complexes of benzothiazolines

      Archana Garg J P Tandon

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      Different molar reactions of Fe(OPr1)3, and FeCl3 with benzothiazolines having an NSH donor system. derived by the condensation ofo-aminothiophenol with heterocyclic aldehydes. viz. pyridine-2-aldehyde. furfuraldehyde and thiophene-2-aldehyde. lead to the formation of [Fe.Pr1(NS)2]2, [Fc(NS)3] and [Fe(NS)2Cl¦ type of complexes. The resulting derivatives have been characterized by elemental analysis, conductivity measurements, molecular weight determinations and magnetic studies. IR, electronic, Mössbauer and ESR spectral data have been used to deduce the structures of the resulting derivatives.

    • Synthesis and characterization of di- and triorganotin(IV) complexes of 2-tert-butyl-4-methyl phenol

      Neeraj Sharma Archana Maridula Thakur S S Bhatt S C Chaudhry

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      The di- and trialkyltin(IV) complexes of composition R2SnCl$_{2-x}$(OAr), and 𝑛-Bu3Sn(OAr) (R = 𝑛-Bu and Me; 𝑥 = 1 and 2; OAr = OC6H3Bu$^t$-2-Me-4) have been synthesized by the reactions of di-n-butyl and dimethyltin dichlorides and tri-n-butyltin(IV) chloride with 2-tert-butyl-4-methylphenol and triethylamine in tetrahydrofuran. The reaction of triphenyltin chloride with trimethylsilyl-2-t-butyl-4-methylphenoxide in the same solvent however, gives a complex of composition Ph3Sn(OAr). The complexes have been characterized by microanalyses, molar conductance measurements, molecular weight determinations and IR and 1H, 13C and 119Sn NMR and mass spectral studies. Thermal behaviour of the complexes has been studied by TGA and DTA techniques. From the non-isothermal TG data, the kinetic and thermodynamic parameters have been calculated employing Coats-Redfern equation and the mechanism of decomposition has been computed using non-isothermal kinetic method. Thermal investigations on the blends of poly(methylmethacrylate). PMMA, with organotin(IV)-2-tert-butyl-4-methylphenoxides have shown increased thermal stability compared to pure PMMA suggesting thereby their potential as additives towards PMMA.

    • Synthesis of Diphenyl Pyridazinone-based flexible system for conformational studies through weak noncovalent interactions: Application in DNA binding


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      This paper reports conformational studies of pyridazinone-based flexible dimer connected throughdiethylamine linker. The conformational studies have been done by X-ray crystal structure and DFT calculation.Further, after crystallization, the compound has shown two types of crystals, one is hydrated and anotherone is non-hydrated. The hydrated and non-hydrated crystals showed difference in their conformation due tothe presence of water in crystal lattice of hydrated crystal. The difference in their conformation has been provedby crystallographic studies, DSC curves and detailed analysis of Hirshfeld surfaces and fingerprint plots facilitatinga comparison of intermolecular interactions. Along with conformational studies, this compound alsoshowed DNA binding, as revealed in docking simulation studies.

    • Controlling the quantum rotational dynamics of a driven planar rotor by rebuilding barriers in the classical phase space


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      The present work aims to control the rotational excitations of an ac-driven planar rotor, a model for rigid diatomic molecules, by rebuilding barriers in the classical phase space. The barriers are invariant tori with irrational winding ratios which are perturbatively constructed at desired locations in the phase space. Weestablish that constructing such barriers, equivalent to additional weak fields, can efficiently suppress the chaos leading to the control of various processes. The phase space barriers are shown to be effective in controlling the quantum dynamics as well. In particular, the efficiency of the phase space barriers towards controlling dynamical tunneling in the system is explored. Our studies are relevant to understanding the role of the chaotic regions in dynamical tunneling and for molecular alignment using bichromatic fields.

    • Stannous chloride catalyzed synthesis of Schiff bases from hydroxybenzaldehydes and determination of their antioxidant activity by ABTS and DPPH assay


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      Phenolic compounds play a very important role in human life because of their antioxidant activity which can prevent harmful diseases caused by free radicals. In the present work, we have synthesized some Schiff bases by the reaction of different hydroxybenzaldehydes and primary aromatic diamines using StannousChloride (SnCl2·2H2O) as the catalyst. The products were characterized by FT-IR spectroscopy, GCMS and NMR spectroscopy. Furthermore, the antioxidant activity of the Schiff bases were determined by using DPPH assay and ABTS assay and the results were compared with a standard compound, trolox as well as with the parent aldehydes. The synthesized compounds were found to have better antioxidant activity than their corresponding parent aldehydes.

    • Study of photophysical behaviour of some Sm(III) complexes with 4- oxo-4H-1-benzopyran-3-carboxaldehyde and other N,N¢-donor pconjugated ligands


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      Trivalent lanthanide ions show interesting optical properties. Keeping this in view, five Sm(III) complexes were synthesized using 4-oxo-4H-1-benzopyran-3-carboxaldehyde (L) as primary ligand along with 1,10-Phenanthroline (Phen); Bipyridine (Bipy); Bathophenanthroline (Bathophen) and Neocuproine(Neo) as secondary ligands. Characterizations of prepared complexes were carried out by means of FTIR, elemental analysis, UV–vis, ESI-MS+, thermal studies, PXRD, FESEM, and luminescence studies. Thermal studies confirmed the good thermal stability of complexes. Sharp peaks in X-ray diffractograms suggest their crystalline nature. The photoluminescence process in complexes has been thoroughly studied and discussed in liquid and powder state. The complexes show 4G5/2®6Hj transitions where j = 5/2, 7/2, and 9/2, analogous tocharacteristic emission peaks of Sm(III) ion at ~ 566, 601, and 648 nm, respectively. The complexes demonstrate intense emission peaks at ~ 601 in liquid and ~ 648 nm in a powder state, which is responsiblefor bright orange and red emission, respectively. The synergistic effect of secondary ligands was responsible for longer luminescence lifetime and enhanced emission intensity in ternary complexes. Attractive photoluminescenceproperties of complexes could play a vital role in electroluminescent devices, bio-assays, liquid lasers, OLEDs, etc.

    • Synthesis, characterization, DNA-binding and biological studies of novel titanium (IV) complexes


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      A series of novel binuclear titanium (IV) complexes, [Ti(sal)LI-V(OBu)(l-OBu)]2, was synthesized by the reaction of salicylic acid (H2sal) and substituted indoles (LI = Tryptophol, LII = 5-Methoxyindole, LIII = Indole-5-Carboxaldehyde, LIV = 5-Cyanoindole, LV = 6-Nitroindole) with titanium(IV) tetrabutoxide in predetermined molar ratios under stirring and refluxing conditions in THF solvent.The chemical structure of synthesized complexes was found to be binuclear based on the FTIR, IH (proton) NMR and ESI-Mass (Electron-spray ionization) spectroscopic data. Each titanium metal was surrounded by two bridged butoxy groups and one terminal butoxy group along with bidentate salicylic acid and coordinated substituted indoles. These complexes were investigated for antioxidant potential using DPPH (2,2-diphenyl-1-picrylhydrazyl) assay where they exhibited moderate to good antioxidant activity. Gel electrophoresismethod was employed to study the ct-DNA (calf thymus DNA) cleavage efficiency of complexes using an agarose gel. Antimicrobial results stated that most of the complexes were ineffective against selected bacterial and fungal strains. Complexes were investigated for anticancer activity against two selected cancerous cell lines (L6 and L929). From MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay, it has been inferred that complexes 1 and 2 have better anticancer properties than their respective indoles. The DNAbinding study of synthesized complexes studied in order to check their efficacy to hinder DNA replication/transcription using electronic absorption and fluorescence spectroscopy revealed them as electrostatic/groove binder. The synthesized complexes were also evaluated for antidiabetic properties using alphaamylaseinhibition assay and complex 5 possessed better alpha-amylase inhibition activity than other complexes.

    • Pyruvic acid-catalyzed one-pot three-component green synthesis of isoxazoles in aqueous medium: a comparable study of conventional heating versus ultra-sonication


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      A mild and efficient route for the one-pot synthesis of isoxazole derivatives has been developedusing pyruvic acid as a catalyst under an aqueous medium. The reaction was carried out under conventional aswell as ultrasonic conditions to afford the desired product in good yield. The features of this protocol are theuse of environmental-friendly, commercially available, biodegradable catalyst, use of biologically safe solvent, simple experimental procedure and short reaction times. The given protocol can be a better alternativefor the synthesis of 4H-isoxazol-5-one derivatives as compared to traditional methods.

      Synopsis: A mild and efficient route for the one pot synthesis of isoxazole derivatives has been developed using pyruvic acid as a catalyst under aqueous medium. The reaction was carried out under conventional as well as ultrasonic condition to afford the desired product in good yield.

    • New cyclam based Zn(II) complexes: effect of flexibility and para substitution on DNA binding, in vitro cytotoxic studies and antimicrobial activities


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      A series of macrobicyclic binuclear Zn(II) complexes were synthesized from their macrocyclicligand (L1 and L2) by Schiff base condensation with appropriate aliphatic or aromatic diamines, ZnCl2.4H2O,and triethylamine. All the complexes were characterized by elemental and spectral analysis. The enhanced DNA binding affinity of complexes [Zn2L1a], [Zn2L1c], and [Zn2L1d] is due to the existence of the electron donating CH3 group, which leads to hydrophobic interaction with the hydrophobic DNA surface. The existence of electron-withdrawing Br atom in complex [Zn2L2a], [Zn2L2c], and [Zn2L2e] leads to lesser DNA binding affinity. The fluorescence quenching of the Zn(II) complex at 370 nm indicates the strong coordination of metal ions with N and O atoms of the ligand. The 3D fluorescence spectrum of [Zn2L2d] complexhas been quenched more compared to [Zn2L2a] due to the planarity of aromatic system. DNA cleavage of Zn(II) complexes begins at a low concentration (25 μM) and reaches the maximum cleavage with a successive increase in concentration (100 μM). All the complexes were screened for antimicrobial and anticancer activity.

      Macrobicyclic binuclear zinc(II) complexes synthesized from their macrocyclic ligands by Schiff base condensation were characterized by elemental and spectral analysis. The enhanced DNA binding affinity (CH3 group) and lesser DNA binding affinity (Br group) have been explained. The 3D fluorescence spectrum shows quenching due to the planarity of aromatic system. DNA cleavage and in vitro activities have been discussed.

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