Palladium-Catalyzed 8-Exo Trig Intramolecular Heck Reaction Under Microwave Irradiation in the Presence of Basic Alumina

The Heck cross-coupling reaction has been employed for efficient conversion of quinolines to benzoxocinoquinoline through a microwave-assisted palladium-catalyzed intramolecular cyclization in the presence of basic alumina.     

Biologically sustainable rubber resin and rubber‐filler promoter: a precursor study

Enthused by the ever growing demand for sustainable and green based materials in responding to applications based on macromolecules, an attempt was made in seeking a bio‐resin (Terpene). Herein, we report the functionalization of bio‐resin with natural rubber (NR) to produce new sustainable and greener functional polymer. Bio‐resin functionalized NR was prepared by melt mixing using di(2‐tert butyl peroxy isopropyl) benzene initiator. Structure elucidation of the bio‐resin functionalized NR was established by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy, respectively. Bio‐resin functionalized NR facilitates the augmented interaction with highly dispersible silica. Amended state of highly dispersible silica dispersion has been achieved in the absence of toxic process oil, expensive silane coupling agent and conventionally used zinc oxide. Remarkable improvement in overall properties corroborated with various meticulous characterization including nanoindentation, rheological, physico‐mechanical and small angle X‐ray scattering using Becauge model, etc. The dynamic mechanical properties of the greener polymer demonstrated low rolling resistance coupled with high traction. More decisively, the macromolecule system toned up sparingly in the presence of the bio‐resin. Our contribution facilitates a novel avenue to develop sustainable high‐performance elastomeric macromolecule. Copyright © 2017 John Wiley & Sons, Ltd.     

Protein adsorption capability of zinc ferrite nanoparticles formed by a low-temperature solution-based process

We report successful synthesis of zinc ferrite nanoparticles (ZFs) by a facile low-temperature (90 °C) solution-based process from ferric nitrate nonahydrate and zinc nitrate hexahydrate precursors in presence of hydrazine hydrate. X-ray diffraction analysis and transmission electron microscopy confirmed the presence of ZFs, which were further characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric measurements for identification of characteristic chemical bond vibrations and thermal weight loss behavior, respectively. Measurements of magnetic properties at room temperature revealed that the sample showed quite high saturation magnetization (22.0 emu/g at ~19,200 G), implying the presence of less impurities/surface defects in the ZFs. The material also showed zero coercivity as a soft-magnetic material. The protein adsorption performance of the ZFs was checked using bovine serum albumin (BSA) as model protein. Excellent protein adsorption capacity of 210 mg/g (close to the value of 218.81 mg/g calculated using the Langmuir model) for BSA concentration of 0.3 mg/mL was obtained at optimized solution pH of 5. This simple process could be adopted for synthesis of different magnetic nanomaterials for use in biomedical applications.     

Simultaneous Presence of Both Open Metal Sites and Free Functional Organic Sites in a Noncentrosymmetric Dynamic Metal–Organic Framework with Bimodal Catalytic and Sensing Activities

Assimilation of open metal sites (OMSs) and free functional organic sites (FOSs) with a framework strut has opened up a new route for the fabrication of novel metal–organic materials, thereby providing a unique opportunity to explore their multiple functionalities. A new metal–organic framework (MOF), {[Cu(ina)₂(H₂O)][Cu(ina)₂(bipy)]?2 H₂O}_n ( 1 ) (ina=isonicotinate, bipy=4,4′‐bipyridine), has been synthesized and characterized. Complex 1 is crystallized in the orthorhombic noncentrosymmetric space group Aba2 and consists of two different 2D coordination polymers, [Cu(ina)₂(H₂O)]_n and [Cu(ina)₂(bipy)]_n, with entrapped solvent water molecules. Hydrogen‐bonding interactions assemble these two different 2D coordination layers in a single‐crystal structure with interdigitation of pendant 4,4′‐bipy from one layer into the groove of another. Upon removal of guest molecules, 1 undergoes a structural transformation in single‐crystal‐to‐single‐crystal fashion with expansion of the effective void space. Each metal center is five‐coordinated and thus can potentially behave as an OMS, and the free pyridyl groups of pendant 4,4′‐bipy moieties and free ? C?O groups can act as free FOSs. Thus, owing to presence of both OMSs and free FOSs, the framework exhibits multifunctional properties. Owing to the presence of OMSs, the framework can act as a Lewis acid catalyst as well as a small‐molecule sensor material, and in a similar way, owing to the presence of free FOSs, it performs as a Lewis base catalyst and a cation sensor material. Furthermore, owing to noncentrosymmetry with large polarity along a particular direction, it shows strong second‐harmonic generation/nonlinear optical (SHG‐NLO) activity.     

Synthetic aspects, crystal structures and antibacterial activities of manganese(III) and cobalt(III) complexes containing a tetradentate Schiff base

Three new Schiff base complexes, namely [Mn(L)Cl] · H₂O (1), [Co(L)Cl]₂ · 2CH₃COCH₃ (2) and [Co(L)NCS]₂ (3), where H₂L = 2,2′-[propane-1,2-diylbis(nitriloeth-1-yl-1-ylidene)]diphenol, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by reacting equimolar amounts of the respective metal chloride and the tetradentate Schiff base ligand (H₂L). While the mononuclear Mn(III) complex 1 was obtained with MnCl₂ in acetone medium, the same synthetic system yielded the binuclear Co(III) complex 2 in the presence of CoCl₂. Dissolution of 1 and 2 followed by crystallization with ammonium thiocyanate in methanol yielded two isostructural phenoxo-bridged binuclear complexes, namely [Mn(L)NCS]₂ (previously reported by us) and a new complex [Co(L)NCS]₂ (3), respectively. All the complexes 1–3 have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 adopts a distorted tetragonal pyramidal geometry while 2 and 3 comprise dimeric Co(III) units with bridging phenolate oxygen atoms. All the complex units in 1–3 and the respective solvent molecules are held together by weak intermolecular H-bonding to constitute a supramolecular network in the solid state. The antibacterial activity of the complexes has been tested against some Gram(+) and Gram(?) bacteria.     

Synthesis, structure, photochromism and DFT calculations of copper(I)-triphenylphosphine halide complexes of thioalkylazoimidazoles

[Cu(SRaaiNR′)(PPh₃)X] complexes are synthesized by the reaction of CuX (X = Cl, Br, I), triphenylphosphine and 1-alkyl-2-[(o-thioalkyl)phenylazo]imidazole (SRaaiNR′). The single crystal X-ray structure of [Cu(SEtaaiNH)(PPh₃)I] (SEtaaiNH = 2-[(o-thioethyl)phenylazo]imidazole) shows a distorted tetrahedral geometry of the copper center with bidentate, N(azo), N(imidazole) chelation of SEtaaiNH and coordination from PPh₃ and iodine. These complexes show a trans-to-cis isomerization upon irradiation with UV light. The reverse transformation, cis-to-trans isomerization, is very slow with visible light irradiation and is thermally accessible. The quantum yields (?_t→c) of the trans-to-cis isomerization of [Cu(SRaaiNR′)(PPh₃)X] are lower than the free ligand values. This is due to the increased mass and rotor volume of the complexes compared to the free ligand data. The rate of isomerization follows the order: [Cu(SRaaiNR′)(PPh₃)Cl] < [Cu(SRaaiNR′)(PPh₃)Br] < [Cu(SRaaiNR′)(PPh₃)I]. The activation energy (E_a) of the cis-to-trans isomerization is calculated by a controlled temperature reaction. DFT computation of representative complexes has been used to determine the composition and energy of the molecular levels.     

Selective extraction of palladium(II) using hydrazone ligand: A novel fluorescent sensor

The acyclic tridentate blue luminescent ligand (λ_ex=300 nm, λ_em=415 nm) quinoline-2-carboxaldehyde 2-pyridylhydrazone, HL, 1, was recognized as a new fluorescent chemosensor for Pd²⁺. In alkaline methanol complete fluorescent quenching was observed in the presence of 2 equivalents of Pd²⁺ that was further reflected in the solid phase fluorescence microscopic study.Ligand formed 1:1 complexes with Ni²⁺, Cu²⁺, Zn²⁺, Pd²⁺ and 1:2 complexes with Co²⁺, Fe²⁺ as obtained from Job's plot of continuous variation. The binding constants of different metal complexes (Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pd²⁺) were estimated by fluorescence titrations. The ligand can selectively extract significant amount of Pd²⁺ from the aqueous mixture of metal ions, and the extraction efficiency was increased from 80% to 95% with increase in the molar ratio of HL, 1, to Pd²⁺ from 1 to 3. No significant interference was observed up to 2-fold excess addition of Cu²⁺ and Zn²⁺ and 100-fold excess addition of Co²⁺, Fe²⁺ and Ni²⁺over the Pd²⁺ ion concentration (1.0×10⁻³ M).     

Poisson convergence of eigenvalues of circulant type matrices

We consider the point processes based on the eigenvalues of the reverse circulant, symmetric circulant and k-circulant matrices with i.i.d. entries and show that they converge to a Poisson random measures in vague topology. The joint convergence of upper ordered eigenvalues and their spacings follow from this. We extend these results partially to the situation where the entries are come from a two sided moving average process.     

Supersymmetric quantum mechanics for two-dimensional disk

The infinite square well potential in one dimension has a smooth supersymmetric partner potential which is shape invariant. In this paper, we study the generalization of this to two dimensions by constructing the supersymmetric partner of the disk billiard. We find that the property of shape invariance is lost in this case. Nevertheless, the WKB results are significantly improved when SWKB calculations are performed with the square of the superpotential. We also study the effect of inserting a singular flux line through the center of the disk.     

Theoretical study on the ground and excited states of dicyanocarbene (C3N2) and its isomers: a low-temperature matrix emission spectrum attributable to 3-cyano-2H-azirenylidene

Ab initio calculations are used to characterize the ground and low lying excited electronic states of selected dicyanocarbene (C(3)N(2) or C(CN)2) isomers. Our calculated ground state geometries and the corresponding vibrational frequencies agree well with available experimental and theoretical data, thereby providing the reliability of the predicted quantities. The present calculations are used to identify the possible emitting species for some unidentified emission bands observed in certain low-temperature matrices. It is found that the 1(3)A' --> X(1)A' transition of 3-cyano-2H-azirenylidene, that is, cyclic C(2)N-CN (Figure 1c) satisfactorily explains all of the observed spectral features of these bands.