Exploration of Metal-Metal Charge Transfer (MMCT) and its Effect in Generating New Colored Compounds in Mixed Metal Oxides

Compounds belonging to the palmierite structure, (Zn_3−xM_x)A₂O₈ (M=Co, Ni, Cu and A=V, P) have been prepared employing solid state methods. The transition metal substituted compounds of Zn₃V₂O₈ exhibits colors that are unique varying from mint green to forest green for Co²⁺ ions. The observed colors were understood based on the allowed d-d transitions and metal to metal charge transfer (MMCT) transitions. The MMCT transitions involve partially filled d-orbitals of Co²⁺ (3d⁷), Ni²⁺ (3d⁸), and Cu²⁺ (3d⁹) ions and the V⁵⁺ ions (3d⁰). The spinel compounds, Zn_2−xCo_xMO₄ (M=Ti, Sn) were also prepared to understand the MMCT transitions in the compounds. Band structure calculations were carried out to understand the participating orbitals near the Fermi level and the band gap. The calculations support the idea that the substitution of transition elements in the palmierite structure reduces the overall band gap from 3.18 eV for Zn₃V₂O₈ to 2.61 eV Zn_2.5Co_0.5V₂O₈ compound. This indicates the substitution of transition elements provide a tool towards band gap engineering.     

A formal convergent synthesis of (+)-trans-solamin

A formal convergent synthesis of solamin is disclosed. The synthetic strategy exploits the potential of the sulfinyl group as an auxiliary, nucleophile and in C-C bond formation. The synthetic route can be adapted to the synthesis of stereoisomers of solamin, analogs with variable carbon side chains, and other members of mono-THF acetogenins.     

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Facile synthesis and magnetic properties of manganese doped ZnS nanorods

The synthesis of both Mn(II) doped and undoped ZnS nanorods were carried out using a simple soft-chemical route using mercaptoethanol as capping agent. Their morphological, structural and magnetic properties are presented. The crystal structures of the as obtained products were investigated through X-ray diffraction study reveals the formation of hexagonal wurtzite structure. The growth of the nanorods is achieved by careful control over the precursor addition, temperature and time duration. The nanorods are single crystalline and the diameter of the rods was found to vary in the range of 20-50 nm. Vibrating sample magnetometer measurements at room temperature show paramagnetic behavior for the doped nanorods.     

Mott localization nurtures several competing and coexisting orders

Band insulating diamond or metallic mercury differs in a fundamental fashion from materials containing Mott localized electrons. Proliferation of long range orders that compete and sometimes coexist is an important consequence of Mott localization. In this article we focus on how Mott localization creates a rich phase diagram and new physics. A projected nature of the low energy Hilbert space, as opposed to a Fermi gas like Hilbert space, underlies this. Spin, orbital and charge degree of freedom gain independence, but get quantum entangled among themselves and create novel phases. We focus on spin-half single orbital systems. Mott localization encourages entanglement of spin pairs via valence bond formation. We relate valence bond dynamics to emergent gauge fields. Emergent gauge fields in turn nurture and encourage a variety of orders, including topological orders: antiferromagnetism, spin liquids, charge, spin stripes, chiral order and robust superconducting order.     

Antimicrobial Lipids from the Hemolymph of Brachyuran Crabs

The potential of marine crabs as a source of biologically active products is largely unexplored. In the present study, antimicrobial activity of the hemolymph (plasma) and hemocytes (plasma cells) of six brachyuran crabs was investigated against 16 pathogenic strains. Among the 16 strains tested maximum zone of inhibition was recorded in the hemolymph of Hyas araneus against Shigella flexineri. Interestingly Staphylococcus aureus and Salmonella typhi were susceptible to all the hemolymph and hemocytes samples. Likewise, the highest zone of inhibition was exhibited by both hemolymph and hemocytes samples against Vibrio cholerae. On the basis of TLC, ¹HNMR, and ¹³CNMR it may be concluded that the antimicrobial activity in the hemolymph extract is due to the presence of lipids. This observation is further supported by the ESI-MS of the methanolic extract of hemolymph of H. araneus. ESI-MS shows cluster of peaks in the region m/z 445 to m/z 491 due to lysoglycerolipids/glycerides and cluster of signals between m/z 216 and 246, due to fatty acids/esters present in the sample.     

Synthesis and properties of thienopyrrole based heteroacenes--indolodibenzothienopyrrole and dicarbazolodithienopyrrole

We report the syntheses and properties of thienopyrrole based unsymmetrical and extended heteroacenes, which are isoelectronic with heptacene (30π) and nonacene (38π), respectively. Optical and electrochemical properties of these seven and nine rings fused systems are studied. The optoelectronic properties of the syn and anti-isomers of the unsymmetrical heteroacenes are also compared. The influence of the position of the heteroatoms in the fused corona, upon the optical and electrochemical properties, is rationalized based on the contributions from the benzenoid vs. quinonoid-type structures of these molecules.     

Synthesis and photovoltaic properties of a furan-diketopyrrolopyrrole-fluorene terpolymer

We report the synthesis of two solution-processable reduced band gap donor–acceptor conjugated polymers p(C8-DPP-F) and p(C12-DPP-F), composed from 9,9-dioctylfluorene as the donor moiety, diketopyrrolopyrrole (DPP) moiety as the acceptor moiety and furan bridges. Two different alkyl chains, n-dodecyl and n-octyl were used on the DPP moiety and the impact of this structural modification evaluated in detail. Both polymers exhibited similar optical and electrochemical properties with optical band gap of around 1.75 eV as result of LUMO levels near −3.4 eV and high-lying HOMO levels of ∼5.2 eV. Bulk heterojunction photovoltaic devices using these polymers electron donors along with PC₇₀BM as the electron acceptor, gave power conversion efficiency of 1.60% and 0.75% for p(C12-DPP-F) and p(C8-DPP-F) respectively.     

Cross-phase modulational instability in an elliptical birefringent fiber with higher order nonlinearity and dispersion

We obtain conditions for the occurrence of cross-phase modulational instability in the normal dispersion regime for the coupled higher order nonlinear Schrödinger equation with higher order dispersion and nonlinear terms.