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Shiv Nadar University

(SoNS) School of Natural Sciences

The synthesis of a new library of 5-arylidenethiazolidinone compounds using an efficient three component reaction with thiazolidine-2,4-dione, piperidine and appropriate aldehydes is reported. This reaction is excellently high yielding, tolerant towards a variety of aldehydes and provides access to these compounds in a single step (in comparison to low yielding multistep syntheses reported in the literature). Once the reaction is complete, the desired product precipitates out of the reaction mixture and is isolated by filtration and purified by washing and recrystallization. These compounds revealed anti-proliferative activities against human breast cancer cells (MCF7 and MDA). Phenotypic profiling established the most active compound 17i (EC50 = 4.52 μM) as an apoptotic agent. A novel chemical proteomics approach identified β-actin-like protein 2, γ-enolase and macrophage migration inhibitory factor (MMIF) as putative cellular binding partners of 17i. © 2016 The Royal Society of Chemistry.

Chemistry

Fulltext

Organic and Biomolecular Chemistry

Synthesis of novel 5-arylidenethiazolidinones with apoptotic properties: Via a three component reaction using piperidine as a bifunctional reagent

A series of benzoxazine monomers with varied benzoxazine functionality from 1 to 3 (mono, bis, and tris) is prepared by reacting agrowaste-derived cardanol with higher functionality amines. The ring opening polymerization study of cardanol-based benzoxazine monomers is investigated by three modes, namely, solution (nuclear magnetic resonance and gel permeation chromatography), bulk (differential scanning calorimetry), and theoretical (B3LYP and 6–31+G**) calculations to analyze the role of number of benzoxazine functionality in curing behavior of the monomers. It is found that the presence of higher and close vicinity of benzoxazine functionality in the monomer promotes faster ring opening, rapid polymerization conversion, and enhancement in the average molecular weight buildup. The activation energy for the curing process is found to decrease from 144–113 kJ mol−1 from mono- to tris-benzo­xazine monomer. Thermodynamically, the presence of higher benzoxazine moiety reveals the curing process is highly exergonic as supported by theoretical calculations. Free energy for successive protonation varies from −9.54 to −24.68 eV for mono- to tris-functionalized monomer. The effect of number of functionality in monomer on its curing behavior – a complete study is reported to offer sustainable monomers/polymers for futuristic materials applications. (Figure presented.) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Macromolecular Chemistry and Physics

Kinetics behind a Strategy for Modulation of Sustainable Benzoxazines: Experimental Study and Its Theoretical Verification

Macromol. Chem. Phys. 12/2016

Several donor (D)-acceptor (A) based molecules are rationally designed by adopting three different schemes in which the conjugation length, strength of the donor and acceptor moieties, and planarity of the molecules are varied. These variations are made by introducing a π-conjugated linkage unit, terminating the ends of the moieties by different electron donating and accepting functional groups, and fusing the donor and acceptor moieties, respectively. Our DFT and TDDFT based calculations reveal that using the above-mentioned design schemes, the electronic and optical properties of the D-A based molecules can be largely tuned. While introduction of a linkage and fusing of moieties enhance the π-π interaction, addition of electron donating groups (-CH3, -OH, and -NH2) and electron accepting groups (-CF3, -CN, -NO2, and -NH3+) varies the strength of the donor and acceptor moieties. These factors lead to modulation of the HOMO and LUMO energy levels and facilitate the engineering of the HOMO-LUMO gap and the optical gap over a wide range of ∼0.7-3.7 eV. Moreover, on the basis of calculated ionization potential and reorganization energy, most of the investigated molecules are predicted to be air stable and to exhibit high electron mobility, with the possibility of the presence of ambipolar characteristics in a few of them. The results of our calculations not only demonstrate the examined molecules to be the potential materials for organic opto-electronic devices, but also establish an understanding of the composition-structure-property correlation, which will provide guidelines for designing and synthesizing new materials of choice. © the Owner Societies 2016.

Physics

Physical Chemistry Chemical Physics

Rationally designed donor-acceptor scheme based molecules for applications in opto-electronic devices

In this paper, effects of lattice strain on dielectric properties of Sr1-xCaxBi2Nb2O9 (x = 0.0-0.5 in steps of 0.1) ceramics are reported. High frequency dipolar polarization is observed to increase for 10\% calcium addition and suppresses thereafter on higher calcium concentrations. The dielectric loss values for all doped samples were lower compared to undoped one at frequencies beyond 1 kHz. The sample with x = 0.1 shows room temperature dielectric constant in the range (130±12) over a wide frequency range from 50 Hz to 1MHz also minimum dielectric loss among all other sample for the same frequeny range. Remarkable increase in Curie temperature (Tc) by 50°C is recorded in the present work by increasing 10\% calcium content in SBN compostion. All higher doped samples indicate increase in Tc by further higher amount. In addition, dc conductivity of all samples is measured for all samples and increase in calcium content is observed to generate more insulating compositions compared to undoped SBN with higher intrinsic activation energies. © The Author(s).

Journal of Advanced Dielectrics

Lattice strain driven dielectric insulation response of Sr1-xCaxBi2Nb2O9 ceramics

Spin-spin correlations and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14 have been investigated by powder neutron diffraction. The present study reveals a three-dimensional long-range magnetic ordering below 16 K where the magnetic structure consists of ferromagnetic trimers that are coupled ferromagnetically along the spin-chain direction (b axis). The moment components along the a and c axes arrange antiferromagnetically. Our study establishes that the uncompensated moment components along the b axis (mb) result in a net magnetization per unit cell. The magnetic structure, determined in the present study, is in agreement with the results of recent first-principles calculation; however, it is in contrast to a fascinating experimental prediction of ferrimagnetic ordering based on the periodicity of the exchange interactions in CaNi3P4O14. Our study also confirms the presence of broad diffuse magnetic scattering, due to one-dimensional short-range spin-spin correlations, over a wide temperature range below ∼50 K down to a temperature well below the Tc. Total neutron scattering analysis by the reverse Monte Carlo (RMC) method reveals that the dominating spin-spin correlation above Tc is ferromagnetic and along the b axis. The nearest-neighbor spin-spin correlations along the a and c axes are found to be weakly antiferromagnetic. The nature of the trimer spin structure of the short-range ordered state (above Tc) is similar to that of the 3D long-range ordered state (below Tc). The present investigation of microscopic nature of the magnetic ground state also explains the condition required for the 1/3 magnetization plateau to be observed in the trimer spin chains. In spite of the S=1 trimer chain system, the present compound CaNi3P4O14 is found to be a good realization of a three-dimensional magnet below Tc=16 K with full ordered moment values of ∼2 $\mu$B/Ni2+ (1.98 and 1.96$\mu$B/Ni2+ for two Ni sites, respectively) at 1.5 K.

Physical Review B

Long-range and short-range magnetic correlations and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3 P4 O14

We present a doubly parametric extension of the standard Froggatt-Nielsen (FN) mechanism. As is well known, mass matrices of the up- and down-type quark sectors and the charged lepton sector in the standard model can be parametrized well by a parameter λ which is usually taken to be the sine of the Cabibbo angle (λ = sin θc ≃ 0.225). However, in the neutrino sector, there is still room to realize the two neutrino mass squared differences δ m2sol δ m2atm, two large mixing angles θ12 and θ23, and non-zero θ13. Then we consider an extension with an additional parameter p in addition to λ. Taking the relevant FN charges for a power of λ (= 0.225) and additional FN charges for a power of p, which we assume to be less than one, we can reproduce the ratio of the two neutrino mass squared differences and three mixing angles. In the normal neutrino mass hierarchy, we show several patterns for taking relevant FN charges and the magnitude of p. We find that if sin θ23 is measured more precisely, we can distinguish each pattern. This is testable in the near future, for example in neutrino oscillation experiments. In addition, we predict the Dirac CP-violating phase for each pattern. © 2016 The Author(s).

Progress of Theoretical and Experimental Physics

Double froggatt-nielsen mechanism

We investigate a possibility for explaining the recently announced 750 GeV diphoton excess by the ATLAS and CMS experiments at the CERN Large Hadron Collider in a model with multiple doubly charged particles, that was originally suggested for explaining tiny neutrino masses through a three-loop effect in a natural way. The enhanced radiatively generated effective coupling of a new singlet scalar S with diphoton with multiple charged particles in the loop enlarges the production rate of S in pp → S +X via a photon fusion process and also the decay width Γ(S → γ γ ) even without assuming a tree-level production mechanism. We provide detailed analysis on the cases with or without allowing mixing between S and the standard model Higgs doublet. © The Author(s) 2016.

LHC 750 GeV diphoton excess in a radiative seesaw model

The iron(IV)-oxo (ferryl) intermediate has been amply established as the principal oxidant in nonheme enzymes and the key player in C-H bond activations and functionalizations. In contrast to this status, our present QM/MM calculations of the mechanism of fosfomycin biosynthesis (a broad range antibiotic) by the nonheme HppE enzyme rule out the iron(IV)-oxo as the reactive species in the hydrogen abstraction (H-abstraction) step of the pro-R hydrogen from the (S)-2-hydroxypropylphosphonic substrate. Moreover, the study reveals that the ferryl species is bypassed in HppE, while the actual oxidant is an HO• radical hydrogen-bonded to a ferric-hydroxo complex, resulting via the homolytic dissociation of the hydrogen peroxide complex, Fe(II)-H2O2. The computed energy barrier of this pathway is 12.0 kcal/mol, in fair agreement with the experimental datum of 9.8 kcal/mol. An alternative mechanism involves the iron-complexed hydroxyl radical (FeIII-(HO•)) that is obtained by protonation of the iron(IV)-oxo group via the O-H group of the substrate. The barrier for this pathway, 23.0 kcal/mol, is higher than the one in the first mechanism. In both mechanisms, the HO• radical is highly selective; its H-abstraction leading to the final cis-fosfomycin product. It appears that HppE is prone to usage of HO• radicals for C-H bond activation, because the ferryl oxidant requires a specific H-abstraction trajectory (-FeOH ∼ 180°) that cannot be met for intramolecular H-abstraction. Thus, this work broadens the landscape of nonheme iron enzymes and makes a connection to Fenton chemistry, with implications on new potential biocatalysts that may harness hydroxyl radicals for C-H bond functionalizations. © 2016 American Chemical Society.

Journal of the American Chemical Society

How do Enzymes Utilize Reactive OH Radicals? Lessons from Nonheme HppE and Fenton Systems

This work uses combined quantum mechanical/molecular mechanical and molecular dynamics simulations to investigate the mechanism and selectivity of H2O2-dependent hydroxylation of fatty acids by the P450SPα class of enzymes. H2O2 is found to serve as the surrogate oxidant for generating the principal oxidant, Compound I (Cpd I), in a mechanism that involves homolytic O-O bond cleavage followed by H-abstraction from the Fe-OH moiety. Our results rule out a substrate-assisted heterolytic cleavage of H2O2 en route to Cpd I. We show, however, that substrate binding stabilizes the resultant Fe-H2O2 complex, which is crucial for the formation of Cpd I in the homolytic pathway. A network of hydrogen bonds locks the HO· radical, formed by the O-O homolysis, thus directing it to exclusively abstract the hydrogen atom from Fe-OH, thereby forming Cpd I, while preventing the autoxoidative reaction, with the porphyrin ligand, and the substrate oxidation. The so formed Cpd I subsequently hydroxylates fatty acids at their α-position with S-enantioselectivity. These selectivity patterns are controlled by the active site: substrate's binding by Arg241 determines the α-regioselectivity, while the Pro242 residue locks the prochiral α-CH2, thereby leading to hydroxylation of the pro-S C-H bond. Our study of the mutant Pro242Ala sheds light on potential modifications of the enzyme's active site in order to modify reaction selectivity. Comparisons of P450SPα to P450BM3 and to P450BSβ reveal that function has evolved in these related metalloenzymes by strategically placing very few residues in the active site. © 2016 American Chemical Society.

Emergence of function in p450-proteins: A combined quantum mechanical/molecular mechanical and molecular dynamics study of the reactive species in the H2O2-dependent cytochrome P450SPα and its regio- and enantioselective hydroxylation of fatty acids