Triphenylphosphine chalcogenides as efficient ligands for room temperature palladium(II)-catalyzed Suzuki-Miyaura reaction

A simple catalytic system based on PdCl₂ and triphenylphosphine chalcogenides (PPh₃X; X = O, S, Se) is found to be highly effective (up to 97% isolated yield) in the room temperature Suzuki-Miyaura reactions. Under the same experimental conditions, triphenylphosphine chalcogenides as ligands show superior activities compared to free triphenylphosphine.     

Computational studies on G-quadruplex DNA-stabilizing property of novel Wittig-based Schiff-Base ligands and their copper(II) complexes

A series of mono imine (C=N) group that contained Wittig-based Schiff-Base ligands was optimized using the DFT-based computational method and Gaussian 09 program package. These optimized molecules were docked with Quadruplex DNA (PDB ID: 1KF1) and duplex DNA (PDB ID: 1BNA) using AutoDock Vina program along with the reference molecules. Schiff-Base ligands derived from fused aromatic rings contained amines and precursor aldehyde (PA-5 both Z and E isomers) showed lower binding energy for G-quadruplex DNA among all and N-5 category both Z and E isomer Schiff-Base ligands have shown high selectivity for G-quadruplex DNA over duplex DNA which is a very important phenomenon to develop the G-quadruplex DNA stabilizers. For a few Schiff-Base molecules like Ligand-6 (1-{[2-Hydroxy-5-(2-pyren-1-yl-vinyl)-benzylidene]-amino}-naphthalen-2-ol) of N-5 category both Z and E isomers with groove binding and end stacking modes, molecular dynamic calculations were carried out. The study revealed that Ligand-6 of N-5 category E isomer with groove binding mode has higher stabilizing effect on G-quadruplex DNA in spite of having the higher binding energy value. Among Schiff-Base copper(II) complexes, Complex-3 (E-(1-{[2-Hydroxy-5-(2-pyren-1-yl-vinyl)-benzylidene]-amino}-naphthalen-2-ol)Cu) is having high binding affinity for G-quadruplex DNA as compared to others.

     

A novel tryptamine-appended rhodamine-based chemosensor for selective detection of Hg2+ present in aqueous medium and its biological applications

A novel rhodamine–tryptamine conjugate–based fluorescent and chromogenic chemosensor (RTS) for detection of Hg²⁺ present in water was reported. After gradual addition of Hg²⁺ in aqueous methanol solution of RTS, a strong orange fluorescence and deep-pink coloration were observed. The probe showed high selectivity towards Hg²⁺ compared to other competitive metal ions. The 1:1 binding stoichiometry between RTS and Hg²⁺ was established by Job’s plot analysis and mass spectroscopy. Initial studies showed that the synthesized probe RTS possessed fair non-toxicity and effectively passed through cell walls of model cell systems, viz., human neuroblastoma (SHSY5Y) cells and cervical cells (HeLa) to detect intercellular Hg²⁺ ions, signifying its utility in biological system. The limit of detection (LOD) was found to be 2.1 nM or 0.42 ppb by fluorescence titration. Additionally, the potential relevance of synthesized chemosensor for detecting Hg²⁺ ions in environmental water samples has been demonstrated.

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Existence of Extremizers for a Model Convolution Operator

The operator T, defined by convolution with the affine arc length measure on the moment curve parametrized by \(h(t)=(t,t^{2},\ldots ,t^{d})\) is a bounded operator from \(L^{p}\) to \(L^{q}\) if \((\frac{1}{p}, \frac{1}{q})\) lies on a line segment. In this article we prove that at non-end points there exist functions which extremize the associated inequality and any extremizing sequence is pre compact modulo the action of the symmetry of T. We also establish a relation between extremizers for T at the end points and the extremizers of an X-ray transform restricted to directions along the moment curve. Our proof is based on the ideas of Michael Christ on convolution with the surface measure on the paraboloid.

     

Synthesis of 1,2- and 1,3-dicarboxylic acids via Pd(II)-catalyzed carboxylation of aryl and vinyl C-H bonds

A Pd(II)-catalyzed reaction protocol for the direct carboxylation of benzoic and phenylacetic acid derivatives to form dicarboxylic acids has been developed. The reaction conditions are also applicable for the carboxylation of vinyl C-H bonds. The first C-H insertion Pd-aryl complex from carboxylic acids has been characterized by X-ray crystallography.     

Sigma-chelation-directed C-H functionalizations using Pd(II) and Cu(II) catalysts: regioselectivity, stereoselectivity and catalytic turnover

Recent progress in sigma-chelation directed C-H functionalization from the authors' group is described to illustrate the challenges and opportunities in the development of synthetically-useful catalytic reactions involving C-H activation as the key step. Emphasis is placed on strategies for developing catalysis under mild conditions and controlling regio- and stereoselectivity.     

Observation of Griffiths phase in antiferromagnetic La(0.32)Eu(0.68)MnO3

We report the Griffiths phase (GP) scenario for isovalent doping in antiferromagnetic La(0.32)Eu(0.68)MnO(3). Rietveld refinement of structural data displays strong crystal structural distortion. The dc and ac magnetic studies nicely demonstrate unambiguous aspects of robust GP. The presence of ferromagnetically correlated spin clusters is found above the transition temperature, T(N). The disorder-driven phase inhomogeneity is correlated to strong structural distortion, giving rise to the GP. This is an unique example in manganite where double exchange interaction does not play any role for the observed phenomenon.     

Synthesis of Indolo[2,3-a]quinolizidine-3-One

The title compound 1 has been synthesised through the intermediacy of the salt 5 obtained by acid hydrolysis of the obtically active β-carboline derivative 10,11-cyclohexylidene-12β-hydroxy-13β-(l-tetrahydro-β-carbolinyl)tetrahydrofuran (4).     

Dispersion corrected double high-hybrid and gradient-corrected density functional theory study of light cation–dihydrogen (M+–H2, where M = Li, Na, B and Al) van der Waals complexes

Structure, frequencies, H–H stretching frequency shifts, interaction energy, depth of the potential well and dissociation energy of the light cation–dihydrogen (M⁺–H₂, where M = Li, Na, B, and Al) van der Waals complexes have been studied in detail using dispersion corrected double-hybrid and gradient-corrected density functional methods in conjunction with correlation consistent valence triple-ζ basis set. Equilibrium bond distance and dissociation energy agree very well with the experimental and theoretical values wherever available. The dissociation energies of Li⁺–H₂, B⁺–H₂, Na⁺–H₂, and Al⁺–H₂ van der Waals complexes calculated from the potential energy curves at mPW2PLYP-D/cc-pVTZ level are 4.83, 3.68, 2.42, and 1.25 kcal/mol, respectively, at a distances of 1.95, 2.25, 2.40, and 2.95 Å. Among all these complexes, Al⁺–H₂ complex is comparatively less stable, as their dissociation energy as well as depth of the potential well are smaller compared to others complexes. The symmetry-adapted perturbation theory (SAPT) has been applied to quantify the nature of interactions. The SAPT results show that the contribution of dispersion and induction are significant, although electrostatic dominates.