Synthesis, DNA-binding, Cytotoxicity, Photo Cleavage, Antimicrobial and Docking Studies of Ru(II) Polypyridyl Complexes

Three Ruthenium(II) polypyridine complexes, [Ru(phen)₂(mipc)]²⁺(1), [Ru(bpy)₂(mipc)]²⁺ (2) and [Ru(dmb)₂(mipc)]²⁺(3) [mipc?=?2-(6-methyl-3-(1H-imidazo[4, 5-f][1,10]-phenanthroline-2-yl)-4H-chromene-4-one, phen?=?1,10-phenanthroline,bpy?=?2, 2′bipyridine,dmb?=?4, 4′-dimethyl-2, 2′-bipyridine] have been synthesized and characterized by elemental analysis, IR, UV–Vis, ¹H& ¹³C NMR and mass spectra. The DNA-binding properties of the Ruthenium(II) complexes were investigated by spectrophotometric methods, viscosity measurements and light switch studies. These three complexes have been focused on photo activated cleavage studies with pBR-322 and antimicrobial studies. Experimental results indicate that the three complexes intercalate into DNA base pairs and follows the order of 1?>?2?>?3 respectively. Molecular docking studies also support the DNA interactions with complexes through hydrogen bonding and vander Waal’s interactions. Cytotoxicity studies with Hela cell lines has been revealing about anti tumor activity of these complexes.     

Cu-Mn spinel oxide catalyzed regioselective halogenation of phenols and N-heteroarenes

A novel simple, mild chemo- and regioselective method has been developed for the halogenation of phenols using Cu-Mn spinel oxide as a catalyst and N-halosuccinimide as halogenating agent. In the presence of Cu-Mn spinel oxide B, both electron-withdrawing and electron-donating groups bearing phenols gave monohalogenated products in good to excellent yields with highest para-selectivity. The para-substituted phenol gave monohalogenated product with good yield and ortho-selectivity. N-Heteroarenes such as indoles and imidazoles also gave monohalogenated products with high selectivity. Unlike the copper-catalyzed halogenation, the present method works well with electron-withdrawing group bearing phenols and gives comparatively better yields and selectivity. The Cu-Mn spinel catalyst is robust and reused three times under optimized conditions without any loss in catalytic activity. Nonphenolics did not undergo this transformation.     

Al2O3(1120) surface as a template for the ordered growth of Ni and Co nanoclusters

The morphology and thermal stability of Ni and Co nanoclusters grown by physical vapour deposition on a reconstructed (1120) surface of α-Al(2)O(3) is investigated using non-contact atomic force microscopy (NC-AFM). NC-AFM images reveal that the clean α-Al(2)O(3)(1120) substrate adopts a characteristic (12 × 4) reconstruction when prepared in vacuum at high temperature. Subsequent deposition of Ni and Co onto this substrate at room temperature facilitates the growth of well-ordered metal nanocluster arrays with a preferred inter-cluster distance determined by the (12 × 4) periodicity of the substrate surface. The order in the cluster arrangement remains intact even upon annealing the system to temperatures up to 500 °C indicating a high resistance against sintering. The reconstructed α-Al(2)O(3)(1120) surface can, therefore, serve as an appropriate insulating template for studies of size-dependent magnetic or catalytic effects in a well-defined ensemble of metallic nanoclusters.     

A cubic spline approximation and application of TAGE iterative method for the solution of two point boundary value problems with forcing function in integral form

In this article, we report an efficient high order numerical method based on cubic spline approximation and application of alternating group explicit method for the solution of two point non-linear boundary value problems, whose forcing functions are in integral form, on a non-uniform mesh. The proposed method is applicable when the internal grid points of solution interval are odd in number. The proposed cubic spline method is also applicable to integro-differential equations having singularities. Computational results are given to demonstrate the utility of the method.     

Poly(isobornyl methacrylate‐co‐methyl acrylate): Synthesis and stereosequence distribution analysis by NMR spectroscopy

Copolymerization of isobornyl methacrylate and methyl acrylate ( I/M ) is performed by atom transfer radical polymerization using methyl‐2‐bromopropionate as an initiator and PMDETA/CuBr as catalyst under nitrogen atmosphere at 70 °C. The copolymer compositions determined from ¹H NMR spectra are used to determine reactivity ratios of the monomers. The reactivity ratio determined from linear Kelen–Tudos method and non‐linear error‐in‐variable method, are r_I = 1.25 ± 0.10, r_M = 0.84 ± 0.08 and r_I = 1.20, r_M = 0.82, respectively. 1D, distortion less enhancement by polarization transfer and 2D, heteronuclear single quantum coherence, and total correlation spectroscopy NMR experiments are employed to resolve highly overlapped and complex ¹H and ¹³C{¹H} NMR spectra of the copolymers. The carbonyl carbon of I and M units and methyl carbon of I unit are assigned up to triad compositional and configurational sequences, whereas β‐methylene carbons are assigned up to tetrad compositional and configurational sequences. Similarly, methine carbon of I unit is assigned up to triad level. The couplings of carbonyl carbon and quaternary carbon resonances are studied in detail using 2D hetero nuclear multiple bond correlation spectra. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Experimental study of shape transitions and energy scaling in thin non-Euclidean plates

We present the first quantitative measurements of shape and energy variation in non-Euclidean plates. Using environmentally responsive gel, we construct non-Euclidean disks of constant imposed Gaussian curvature, K(tar). We vary the disks' thickness t(0) and measure the dependence of configurations, surface curvature, and energy content on t(0). For K(tar)<0, configurations are of a single wavy mode and undergo a set of bifurcations that leads to their refinement with decreasing thickness. This leads to sharp increase in the amount of surface bending as t(0)→0, and to a slow decay of both bending and stretching energies. Both vary like t(0)(2), compared with t(0)(3) of the bending energy in disks with K(tar)>0.     

Shape selection in non-Euclidean plates

We investigate isometric immersions of disks with constant negative curvature into R³, and the minimizers for the bending energy, i.e. the L² norm of the principal curvatures over the class of W^2,2 isometric immersions. We show the existence of smooth immersions of arbitrarily large geodesic balls in H² into R³. In elucidating the connection between these immersions and the non-existence/singularity results of Hilbert and Amsler, we obtain a lower bound for the L^∞ norm of the principal curvatures for such smooth isometric immersions. We also construct piecewise smooth isometric immersions that have a periodic profile, are globally W^2,2, and numerically have lower bending energy than their smooth counterparts. The number of periods in these configurations is set by the condition that the principal curvatures of the surface remain finite and grow approximately exponentially with the radius of the disk. We discuss the implications of our results on recent experiments on the mechanics of non-Euclidean plates.     

Gold-catalyzed, intramolecular, oxygen-transfer reactions of 2-alkynyl-1,5-diketones or 2-alkynyl-5-ketoesters: scope, expansion, and mechanistic investigations on a new [4+2] cycloaddition

The gold-catalyzed intramolecular oxygen-transfer reactions of 2-alkynyl-1,5-diketones or 2-alkynyl-5-ketoesters-obtained from tetra-n-butylammonium fluoride mediated Michael addition of activated allenes to electron-deficient olefins-furnished cyclopentenyl ketones under very mild conditions. These reactions proceeded much easier and faster than similar reactions reported in literature, and the corresponding products were obtained in very good yields. Mechanistic investigations on the cycloisomerization were carried out by means of both (18) O isotopic experiments and quantum chemical calculations. The results from both, the designed isotopic experiments and theoretical calculations, satisfactorily supported the novel proposed intramolecular [4+2] cycloaddition of a gold-containing furanium intermediate to a carbonyl group, instead of the previous well-accepted [2+2] pathway.     

Optimization of Nanofluidic Devices for Geometry-Induced Electrostatic Trapping

Nanoparticle trapping in a nanofluidic device utilizing geometry-induced electrostatic (GIE) potential trap is an efficient and robust way to perform nano‑object confinement and single particle studies. The GIE‑trapping is a passive method that solely depends on the device geometry and device-particle surface interaction. Therefore, optimization of a nanofluidic device based on experimental requirements, helps to achieve stiffer single-particle trapping. The efficiency of a GIE‑trapping device is defined in terms of residence time and trapping stiffness of the nanoparticle inside a potential trap. The present study reveals all crucial parameters that affect the device efficiency, particle trapping stiffness, and particle residence time. Furthermore, the trends of particle trapping stiffness are presented as a function of crucial parameters and demonstrate two variants of simulations to estimate the particle trapping efficiency: (a) using charged particle, and (b) using point charge approximation. Simulations with charged particle give more realistic values related to particle trapping whereas simulations with point charge approximation is a faster approach which gives approximate values and a guideline for more rigorous simulations. The results demonstrate a good agreement with experimental observations and hold the key for future developments in this field, wherein a device geometry can be very precisely optimized.     

Recyclability of poly (N-isopropylacrylamide) microgel-based assemblies for organic dye removal from water

Poly (N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgels and their aggregates have been shown to effectively remove organic dye molecules from aqueous solutions. Here, we investigate the reusability of these microgel-based systems by exposing them to the organic azo dye molecule, 4-(2-hydroxy-1-naphthylazo) benzenesulfonic acid sodium salt (Orange II). Following exposure, the microgels are isolated, and added to methanol to extract the trapped Orange II from the microgels, followed by a subsequent isolation. The isolated microgels were then exposed to Orange II once again, and the uptake efficiency of the recycled microgels determined. We found that the microgels and their aggregates could be reused to remove the organic dye with little loss in extraction efficiency with the number of recycling cycles.