Restriction theorems for Higgs principal bundles

We prove analogues of Grauert–Mülich and Flenner?s restriction theorems for semistable principal Higgs bundle over any smooth complex projective variety.     

Encapsulation of trivalent phosphate anion within a rigidified π-stacked dimeric capsular assembly of tripodal receptor

The tris(thiourea) receptor, L, in the presence of excess H(2)PO(4)(-) has been found to encapsulate a trivalent phosphate ion within a π-stacked dimeric capsular assembly of the receptor with twelve strong H-bonds via deprotonation, as evident from the origin of a new set of signals in the (1)H NMR titration experiments.     

An in vitro and in vivo study of a novel zinc complex, zinc N-(2-hydroxyacetophenone)glycinate to overcome multidrug resistance in cancer

Multiple drug resistance (MDR) remains a major clinical challenge for cancer treatment. P-glycoprotein is the major contributor and they exceed their role in the chemotherapy resistance of most of the malignancies. Attempts in several preclinical and clinical studies to reverse the MDR phenomenon by using MDR modulators have not yet generated promising results. In the present study, a co-ordination complex of zinc viz., Zn N-(2-hydroxyacetophenone)glycinate (ZnNG) has been synthesized, characterized and its antitumour activity was tested in vitro against drug sensitive and resistant human T-lymphoblastic leukemic cell lines (CCRF/CEM and CEM/ADR5000 respectively) and in vivo against Ehrlich ascites carcinoma (EAC) implanted in female Swiss albino mice. To evaluate the cytotoxic potential of ZnNG, we used sensitive CCRF/CEM and drug resistant CEM/ADR 5000 cell lines in vitro. Moreover, ZnNG also has the potential ability to reverse the multidrug resistance phenotype in drug resistant CEM/ADR 5000 cell line and induces apoptosis in combination with vinblastine. ZnNG remarkably increases the life span of Swiss albino mice bearing sensitive and doxorubicin resistant subline of EAC in presence and in absence of doxorubicin. In addition, intraperitoneal application of ZnNG in mice does not show any systemic toxicity in preliminary trials in normal mice. To conclude, a novel metal chelate of zinc viz., ZnNG, may be a promising therapeutic agent against sensitive as well as drug resistant cancers.     

Influence of heterogeneity of confined water on photophysical behavior of acridine with amines: a time-resolved fluorescence and laser flash photolysis study

The photophysical behavior of acridine (Acr) shows facilitated water-assisted protonation equilibrium between its deprotonted (Acr* ～ 10 ns) and protonated forms (AcrH(+*) ～ 28 ns) within confined region of ordered water molecules inside AOT/H(2)O/n-heptane reverse micelles (RMs). The time-resolved-area-normalized-emission spectra confirm both Acr* and AcrH(+*), while time-resolved-emission spectra depict time evolution between them. Quenching of AcrH(+*) with N,N-dimethylaniline (DMA) is a purely diffusion-controlled bimolecular quenching with linear Stern-Volmer (S-V) plot, while nonlinearity arises with triethylamine (TEA) that forms ground state complex with AcrH(+) (AcrH(+)··H(2)O··TEA) indicating both static and dynamic quenching. Transient intermediates, DMA(?+) and AcrH(?) infer photoinduced electron transfer from DMA to Acr, while those from AcrH(+)··H(2)O··TEA complex suggest water mediated excited-state proton transfer (ESPT) between AcrH(+) and TEA. The ESPT becomes faster in larger RMs due to enhanced mobility of hydronium ions in AcrH(+)··H(2)O··TEA, which reduces in smaller RMs as water becomes much more constrained owing to stronger complexation by excess confinement.     

Catalytic activity of an iron(III) Schiff base complex bound in a polymer resin

An iron(III)–ferrocene complex and its heterogeneous analogue bound in a polymer resin have been prepared and employed as catalysts for the oxidation of various organic substrates. Characterization of the heterogeneous and homogeneous complexes was done by SEM, EDAX, TGA, FT-IR, DRS-UV, and spectroscopy. The catalyst’s activity, stability, and reusability were investigated through industrially relevant oxidation reactions. The solid iron(III)–ferrocene Schiff base complex gave more effective results than the solid-supported ferrocene Schiff base ligand. The antimicrobial activities of the molecular complex and free ligand were studied for Gram-positive and Gram-negative bacteria.     

POM‐Catalyzed In Situ Ligand Synthesis for the Construction of Metal Complexes and Their Use in the Formation of Coordination Polymers

Six organic–inorganic hybrid materials were synthesized by the in situ oxidation of neocuproine by using MoO₃/Na₂MoO₄ as the catalyst in the presence of Cu(NO₃)₂. The crystal structures of Mo8‐Cu4‐PHEN and Mo8‐Cu2‐5(2PIC) are composed of [Mo₈O₂₆]^4? polyoxometalate (POM) units, whereas the crystal structure of Mo6‐Cu‐COPHEN is composed of a [Mo₆O₁₉]^2? POM unit; both POM units could be considered as the active form of the catalyst. Reaction of the hybrid materials with 1,3,5‐benzenetricarboxylic acid (BTC) resulted in the formation of two different coordination polymers (CPs) under different reaction conditions. These CPs, depending on their structural attributes, exhibit distinct differences in the adsorption of H₂, CO₂, and water. The use of 2‐methylpyridine instead of neocuproine does not give any oxidation products under the same reaction conditions due to the incorrect positioning of the methyl group with respect to the Cu^II center.     

Layer-by-layer electrostatic assembly with a control over orientation of molecules: anisotropy of electrical conductivity and dielectric properties

While forming layer-by-layer (LbL) electrostatic assembly of a magnetic organic molecule, namely, nickel phthalocyanine (NiPc), we apply a magnetic field. The field orients the magnetic moment of the molecules on a monolayer along the direction of magnetic field. Such an orientation of the molecules is then electrostatically immobilized with a monolayer of a polycation. By repeating the dipping cycle, we form LbL films with planar NiPc molecules facing a particular direction. With NiPc's moment perpendicular to the molecular plane, two types of LbL films were formed: (a) NiPc's molecular plane parallel to the substrate (moment is perpendicular) and (b) molecules perpendicular to the substrate and facing one particular direction, the direction of magnetic field. Such films, with the molecules lying either (a) parallel or (b) perpendicular to the substrate, provide unique systems to study anisotropy of optical, dielectric, and electrical characteristics in these planar organic molecules. The latter film responds to the polarization of incident beam in electronic absorption spectroscopy. Here we show methods to obtain an orientation of molecules in LbL films and study anisotropy of dielectric constant and conductivity of the molecules in ultrathin films.     

A multistate switchable [3]rotacatenane

Rotacatenanes are exotic molecular compounds that can be visualized as a unique combination of a [2]catenane and a [2]rotaxane, thereby combining both the circumrotation of the ring component (rotary motion) and the shuttling of the dumbbell component (translational motion) in one structure. Herein, we describe a strategy for the synthesis of a new switchable [3]rotacatenane and the investigation of its switching properties, which rely on the formation of tetrathiafulvalene (TTF) radical π-dimer interactions-namely, the mixed-valence state (TTF(2) )(+.) and the radical-cation dimer state (TTF(+.) )(2) -under ambient conditions. A template-directed approach, based on donor-acceptor interactions, has been developed, resulting in an improved yield of the key precursor [2]catenane, prior to rotacatenation. The nature of the binding between the [2]catenane and selected π-electron-rich templates has been elucidated by using X-ray crystallography and UV/Vis spectroscopy as well as isothermal titration microcalorimetry. The multistate switching mechanism of the [3]rotacatenane has been demonstrated by cyclic voltammetry and EPR spectroscopy. Most notably, the radical-cation dimer state (TTF(+.) )(2) has been shown to enter into an equilibrium by forming the co-conformation in which the two 1,5-dioxynaphthalene (DNP) units co-occupy the cavity of tetracationic cyclophane, thus enforcing the separation of TTF radical-cation dimer (TTF(+.) )(2) . The population ratio of this equilibrium state was found to be 1:1. We believe that this research demonstrates the power of constructing complex molecular machines using template-directed protocols, enabling us to make the transition from simple molecular switches to their multistate variants for enhancing information storage in molecular electronic devices.     

Ag nanoparticle mediated growth of CdS nanobelts

Catalytic growth of CdS have been carried out on large scale by evaporation of bulk CdS on Ag deposited Si (1 1 1) at atmospheric pressure. The as prepared CdS had wurtzite structure as evidenced by X-ray diffraction. The nanostructures were beltlike with several tens of micrometers length, several micrometers width and few nanometers to tens of nanometers thick as seen by scanning electron microscope and confirmed by TEM studies. The nanobelts were single crystalline in nature and showed reflection corresponding to (1 1 2) and (0 0 2) planes in SAED. The PL studies revealed the green band due to band gap emission and red band due to emission from the surface states. The higher intensity of the defect emission indicated the presence of considerable concentration of surface defects in the as prepared sample. The deposition of CdS could be explained on the basis of catalyst assisted vapor-liquid-solid and vapor-solid mechanism.