Enhanced Catalytic Activity and Unexpected Products from the Oxidation of Cyclohexene by Organic Nanoparticles of 5,10,15,20‐Tetrakis‐(2,3,4,5,6‐pentafluorophenyl)porphyrinatoiron(III) in Water by Using O2

The catalytic oxidation of alkenes by most iron porphyrins using a variety of oxygen sources, but generally not dioxygen, yields the epoxide with minor quantities of other products. The turnover numbers for these catalysts are modest, ranging from a few hundred to a few thousand depending on the porphyrin structure, axial ligands, and other reaction conditions. Halogenation of substituents increases the activity of the metalloporphyrin catalyst and/or makes it more robust to oxidative degradation. Oxidation of cyclohexene by 5,10,15,20‐tetrakis‐(2,3,4,5,6‐pentafluorophenyl)porphyrinato iron(III), ([Fe^III(tppf₂₀)]) and H₂O₂ is typical of the latter: the epoxide is 99 % of the product and turnover numbers are about 350. 1 – 4 Herein, we report that dynamic organic nanoparticles (ONPs) of [Fe^III(tppf₂₀)] with a diameter of 10 nm, formed by host–guest solvent methods, catalytically oxidize cyclohexene with O₂ to yield only 2‐cyclohexene‐1‐one and 2‐cyclohexene‐1‐ol with approximately 10‐fold greater turnover numbers compared to the non‐aggregated metalloporphyrin in acetonitrile/methanol. These ONPs facilitate a greener reaction because the reaction solvent is 89 % water and O₂ is the oxidant in place of synthetic oxygen sources. This reactivity is unexpected because the metalloporphyrins are in close proximity and oxidative degradation of the catalyst should be enhanced, thus causing a significant decrease in catalytic turnovers. The allylic products suggest a different oxidative mechanism compared to that of the solvated metalloporphyrins. These results illustrate the unique properties of some ONPs relative to the component molecules or those attached to supports.     

Computation-led design of pollutant gas sensors with bare and carbon nanotube supported rhodium alloys

Quantum chemical study has been performed on finite-sized bi-metallic Rh3M alloys, M = Ag, Ir, Pd, Pt, Au, derived from magic cluster, Rh4. Bond length of C–O and N–O are noticed to be elongated in the presence of rhodium alloy clusters. CO2 and NO2 gases are found to be highly adsorbed on Rh3M clusters, which is confirmed by stretching frequency of C–O and N–O. DFT evaluated dipole moment and electronic charge redistribution suggests the sensing capability of CO2 and NO2 gases by Rh3M clusters which is further confirmed by the calculated HOMO–LUMO gap. Mixed rhodium alloy clusters supported on single-wall carbon nanotube (SWCNT) exhibits much higher ability to sense CO2 and NO2. On the other hand, SWCNT@Rh3M shows higher catalytic activity for the activation of CO2 and NO2 in comparison to bare Rh3M because of the higher electronic charge redistribution in the case of SWCNT@Rh3M. In case of SWCNT-supported gas adsorbed clusters, p electrons play a major role in bonding.     

Highly Mesoporous Metal‐Organic Frameworks as Synergistic Multimodal Catalytic Platforms for Divergent Cascade Reactions

Rational engineering and assimilation of diverse chemo‐ and biocatalytic functionalities in a single nanostructure is highly desired for efficient multistep chemical reactions but has so far remained elusive. Here, we design and synthesize multimodal catalytic nanoreactors (MCNRs) based on a mesoporous metal‐organic framework (MOF). The MCNRs consist of customizable metal nanocrystals and stably anchored enzymes in the mesopores, as well as coordinatively unsaturated cationic metal MOF nodes, all within a single nanoreactor space. The highly intimate and diverse catalytic mesoporous microenvironments and facile accessibility to the active site in the MCNR enables the cooperative and synergistic participation from different chemo‐ and biocatalytic components. This was shown by one‐pot multistep cascade reactions involving a heterogeneous catalytic nitroaldol reaction followed by a [Pd/lipase]‐catalyzed chemoenzymatic dynamic kinetic resolution to yield optically pure (>99 % ee) nitroalcohol derivatives in quantitative yields.     

Self-immolative polymers

Smart polymers are special kinds of polymeric molecules that respond to external stimuli. We have developed a novel smart polymer designed to sequentially disassemble into its building blocks upon initiation by a triggering event at the polymer head. The polymer structure is based on a polyurethane backbone that disassembles through a domino-like, 1,6-elimination and decarboxylation reactions. We synthesized a self-immolative polymer that amplifies a single cleavage reaction into multiple release of fluorogenic molecules and confirmed the head-to-tail disassembly concept. These polymers can be used to prepare highly sensitive molecular sensors with large signal-to-noise ratios. The sensors should be useful for the detection of a wide range of biological and chemical activities through use of the appropriate trigger at the polymer head.     

Model Compounds for Iron Proteins. Structures and Magnetic, Spectroscopic, and Redox Properties of Fe(III)M(II) and [Co(III)Fe(III)](2)O Complexes with (&mgr;-Carboxylato)bis(&mgr;-phenoxo)dimetalate and (&mgr;-Oxo)diiron(III) Cores

A series of heterobimetallic complexes of the type [Fe(III)M(II)L(&mgr;-OAc)(OAc)(H(2)O)](ClO(4)).nH(2)O (2-5) and [{Fe(III)Co(III)L(&mgr;-OAc)(OAc)}(2)(&mgr;-O)](ClO(4))(2).3H(2)O (6) where H(2)L is a tetraaminodiphenol macrocyclic ligand and M(II) = Zn(2), Ni(3), Co(4), and Mn(5) have been synthesized and characterized. The (1)H NMR spectrum of 6 exhibits all the resonances between 1 and 12 ppm. The IR and UV-vis spectra of 2-5 indicate that in all the cases the metal ions have similar coordination environments. A disordered crystal structure determined for 3 reveals the presence of a (&mgr;-acetate)bis(&mgr;-phenoxide)-Ni(II)Fe(III) core, in which the two metal ions have 6-fold coordination geometry and each have two amino nitrogens and two phenolate oxygens as the in-plane donors; aside from the axial bridging acetate, the sixth coordination site of nickel(II) is occupied by the unidentate acetate and that of iron(III) by a water molecule. The crystal structure determination of 6 shows that the two heterobinuclear Co(III)Fe(III) units are bound by an Fe-O-Fe linkage. 6 crystallizes in the orthorhombic space group Ibca with a = 17.577(4) ?, b = 27.282(7) ?, c = 28.647(6) ?, and Z = 8. The two iron(III) centers in 6 are strongly antiferromagnetically coupled, J = -100 cm(-1) (H = -2JS(1).S(2)), whereas the other two S(1) = S(2) = (5)/(2) systems, viz. [Fe(2)(III)(HL)(2)(&mgr;-OH)(2)](ClO(4))(2) (1) and the Fe(III)Mn(II) complex (5), exhibit weak antiferromagnetic exchange coupling with J = -4.5 cm(-1) (1) and -1.8 cm(-1) (5). The Fe(III)Ni(II) (3) and Fe(III)Co(II) (4) systems, however, exhibit weak ferromagnetic behavior with J = 1.7 cm(-1) (3) and 4.2 cm(-1) (4). The iron(III) center in 2-5 exhibits quasi-reversible redox behavior between -0.44 and -0.48 V vs Ag/AgCl associated with reduction to iron(II). The oxidation of cobalt(II) in 4 occurs quasi-reversibly at 0.74 V, while both nickel(II) and manganese(II) in 3 and 5 undergo irreversible oxidation at 0.85 V. The electrochemical reduction of 6 leads to the generation of 4.     

Flexible software reliability growth model with testing effort dependent learning process

A lot of importance has been attached to the testing phase of the Software Development Life Cycle (SDLC). It is during this phase it is checked whether the software product meets user requirements or not. Any discrepancies that are identified are removed. But testing needs to be monitored to increase its effectiveness. Software Reliability Growth Models (SRGMs) that specify mathematical relationships between the failure phenomenon and time have proved useful. SRGMs that include factors that affect failure process are more realistic and useful. Software fault detection and removal during the testing phase of SDLC depend on how testing resources (test cases, manpower and time) are used and also on previously identified faults. With this motivation a Non-Homogeneous Poisson Process (NHPP) based SRGM is proposed in this paper which is flexible enough to describe various software failure/reliability curves. Both testing efforts and time dependent fault detection rate (FDR) are considered for software reliability modeling. The time lag between fault identification and removal has also been depicted. The applicability of our model is shown by validating it on software failure data sets obtained from different real software development projects. The comparisons with established models in terms of goodness of fit, the Akaike Information Criterion (AIC), Mean of Squared Errors (MSE), etc. have been presented.     

Lower bounds for adaptive locally decodable codes

An error‐correcting code is said to be locally decodable if a randomized algorithm can recover any single bit of a message by reading only a small number of symbols of a possibly corrupted encoding of the message. Katz and Trevisan 12 showed that any such code C : {0, 1}ⁿ → Σ^m with a decoding algorithm that makes at most q probes must satisfy m = Ω((n/log |Σ|)^q/(q?1)). They assumed that the decoding algorithm is non‐adaptive, and left open the question of proving similar bounds for adaptive decoders. We show m = Ω((n/log |Σ|)^q/(q?1)) without assuming that the decoder is nonadaptive. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2005     

Ultratrace Analysis of Dopamine Using a Combination of Imprinted Polymer-Brush-Coated SPME and Imprinted Polymer Sensor Techniques

A combination approach in solid-phase microextraction, based on a molecularly imprinted polymer-brush coating on an optical fiber coupled with a complementary molecularly imprinted polymer sensor, has been adopted for isolation, preconcentration, and analysis of dopamine at ultratrace levels in highly dilute aqueous samples. This combination enabled enhanced (up to 8.5-fold) preconcentration of the analyte, which is appropriate for achieving a stringent detection limit in clinical diagnosis of several neurodegenerative diseases. The detection limit of dopamine in biological samples was 0.018 ng mL^?1 with a relative standard deviation less than 2.1% and without any non-specific contributions.     

Zero-Sets of Quaternionic and Octonionic Analytic Functions with Central Coefficients

We prove that the zero set of any quaternionic (or octonionic)analytic function f with central (that is, real) coefficientsis the disjoint union of codimension two spheres in R⁴ or R⁸(respectively) and certain purely real points. In particular,for polynomials with real coefficients, the complete root-setis geometrically characterisable from the lay-out of the rootsin the complex plane. The root-set becomes the union of a finitenumber of codimension 2 Euclidean spheres together with a finitenumber of real points. We also find the preimages f^–1for any quaternion (or octonion) A. We demonstrate that this surprising phenomenon of complete spheresbeing part of the solution set is very markedly a special ‘real’phenomenon. For example, the quaternionic or octonionic Nthroots of any non-real quaternion (respectively octonion) turnout to be precisely N distinct points. All this allows us todo some interesting topology for self-maps of spheres.     

Minimally deformed anisotropic stars by gravitational decoupling in Einstein–Gauss–Bonnet gravity

The European Physical Journal C - Baryon inhomogeneities are generated early in the universe. These inhomogeneities affect the phase transition dynamics of subsequent phase transitions, they also...