Synthesis and supramolecular assembly of the bifunctional borinic acid 1,2-fcB(OH)](2)

Treatment of the chloro-substituted diboradiferrocene derivative 1 with Me3SiOMe and subsequent hydrolysis resulted in formation of the novel organometallic bis(borinic acid) derivative 3. The assembly of 3 into supramolecular structures via hydrogen bonding and reversible covalent boron-oxygen bond formation was explored. Upon crystallization from acetone or THF one-dimensional chains form in which molecules of 3 alternately serve as hydrogen bond donors and acceptors. The additional OH hydrogens that are not involved in hydrogen bonding within the polymeric chains undergo hydrogen bonding to the solvent molecules. Removal of the solvent was achieved at moderate temperature under high vacuum. While the polymeric chains remain intact, in the absence of the solvent as a hydrogen bond acceptor, short contacts to the Cp rings of neighboring polymer strands lead to a network-like structure. At higher temperatures, further dehydration occurs with formation of B-O-B linkages as confirmed by MALDI-TOF mass spectrometry. Oligomers with up to 15 repeating units (30 ferrocenes) were detected.

Tetraethylammonium Tetraselenotungstate: A Versatile Selenium Transfer Reagent in Organic Synthesis

Organoselenium compounds have attracted intense research owing to their unique biological properties as well as pharmaceutical significance. Progress has been made in developing reagents for incorporation of selenium in an efficient and controlled manner. Herein, we present a review on the recently developed selenium reagent, tetraethylammonium tetraselenotungstate, Et4N](2)WSe4 as a versatile selenium transfer reagent in organic synthesis. Tetraselenotungstate has been successfully used for the synthesis of a number of functionalized diselenides, sugar- and nucleoside-derived diselenides, seleno-cystines, selenohomocystines, selenoamides, selenoureas and sugar- and nucleoside-based cyclic-selenide derivatives. Additionally, this reagent has been employed for the ring opening of aziridines to synthesize a variety of beta-aminodiselenides. A new selena-aza-Payne type rearrangement of aziridinemethanoltosylates mediated by tetraselenotungstate for the synthesis of allyl amines is also discussed.

Processing of enriched elemental boron (B-10 similar to 65 at. %)

Procedures were developed for purification and processing of electrodeposited enriched boron powder for control rod application in India's first commercial Proto Type Fast Breeder Reactor (PFBR). Methodology for removal of anionic (F-, Cl-, BF4-) and cationic (Fe2+, Fe3+, Ni2+) impurities was developed. Parameters for grinding boron flakes obtained after electrodeposition were optimized to obtain the boron powder having particle size less than 100 gm. The rate of removal of impurities was studied with respect to time and concentration of the reagents used for purification. Process parameters for grinding and removal of impurities were optimized. A flowsheet was proposed which helps in minimizing the purification time and concentration of the reagent used for the effective removal of impurities. The purification methodology developed in this work could produce boron that meets the technical specifications for control rod application in a fast reactor.

Six-membered C,N] cyclopalladated sym N,N `,N `'-tri(4-tolyl) guanidines: Synthesis, reactivity studies and structural aspects

Six-membered C,N] cyclopalladated sym N,N',N `'-tri(4-tolyl)guanidines, (ArNH)(2)C=NAr] (sym = symmetrical; Ar = 4-MeC6H4; LH24-tolyl) of the types (C,N)Pd(mu-OC(O)R)](2) (1 and 2), (C,N)Pd(mu-Br)](2) (3), cis-(C,N)PdLBr] (4-7), and (C,N)Pd(acac)] (8) were prepared in high yield by established methods with a view aimed at understanding the influence of the 4-tolyl substituent of the guanidine moiety upon the solution behaviour of 1-8. The composition of 1-8 was confirmed by elemental analysis, IR, and NMR spectroscopy, and mass spectrometry. The molecular structures of 1-6 were determined by single-crystal X-ray diffraction. Palladacycles 1-3 exist as a dimer in transoid conformation in the solid state while 4-6 exist as a monomer with cis configuration around the palladium atom as the Lewis base is placed cis to the Pd-C bond due to antisymbiosis. The NMR spectra of 1-8 revealed the presence of a single isomer in solution and this spectral feature is ascribed to the rapid inversion of the six-membered ``C,N]Pd'' ring due to the presence of sterically less hindered and more symmetrical 4-tolyl substituent in the =NAr unit of the guanidine moiety. (C) 2013 Elsevier B.V. All rights reserved.

Fe as Hydrogen/Halogen Bond Acceptor in Square Pyramidal Fe(CO)(5)

Hydrogen bonded complexes formed between the square pyramidal Fe(CO)(5) with HX (X = F, Cl, Br), showing X-H center dot center dot center dot Fe interactions, have been investigated theoretically using density functional theory (DFT) including dispersion correction. Geometry, interaction energy, and large red shift of about 400 cm(-1) in the FIX stretching frequency confirm X-H center dot center dot center dot Fe hydrogen bond formation. In the (CO)(5)Fe center dot center dot center dot HBr complex, following the significant red shift, the HBr stretching mode is coupled with the carbonyl stretching modes. This clearly affects the correlation between frequency shift and binding energy, which is a hallmark of hydrogen bonds. Atoms in Molecule (AIM) theoretical analyses show the presence of a bond critical point between the iron and the hydrogen of FIX and significant mutual penetration. These X-H center dot center dot center dot Fe hydrogen bonds follow most but not all of the eight criteria proposed by Koch and Popelier (J. Phys. Chem. 1995, 99, 9747) based on their investigations on C-H center dot center dot center dot O hydrogen bonds. Natural bond orbital (NBO) analysis indicates charge transfer from the organometallic system to the hydrogen bond donor. However, there is no correlation between the extent of charge transfer and interaction,energy, contrary to what is proposed in the recent IUPAC recommendation (Pure Appl.. Chem. 2011, 83, 1637). The ``hydrogen bond radius'' for iron has been determined to be 1.60 +/- 0.02 angstrom, and not surprisingly it is between the covalent (127 angstrom) and van der Waals (2.0) radii of Fe. DFT and AIM theoretical studies reveal that Fe in square pyramidal Fe(CO)(5) can also form halogen bond with CIF and ClH as ``halogen bond donor''. Both these complexes show mutual penetration as well, though the Fe center dot center dot center dot Cl distance is closer to the sum of van der Waals radii of Fe and Cl in (CO)5Fe center dot center dot center dot ClH, and it is about 1 angstrom less in (CO)(5)Fe center dot center dot center dot ClF.

Gene Transfection in High Serum Levels: Case Studies with New Cholesterol Based Cationic Gemini Lipids

Background: Six new cationic gemini lipids based on cholesterol possessing different positional combinations of hydroxyethyl (-CH2CH2OH) and oligo-oxyethylene -(CH2CH2O)(n)- moieties were synthesized. For comparison the corresponding monomeric lipid was also prepared. Each new cationic lipid was found to form stable, clear suspensions in aqueous media. Methodology/Principal Findings: To understand the nature of the individual lipid aggregates, we have studied the aggregation properties using transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements and X-ray diffraction (XRD). We studied the lipid/DNA complex (lipoplex) formation and the release of the DNA from such lipoplexes using ethidium bromide. These gemini lipids in presence of a helper lipid, 1, 2-dioleoyl phophatidyl ethanol amine (DOPE) showed significant enhancements in the gene transfection compared to several commercially available transfection agents. Cholesterol based gemini having -CH2-CH2-OH groups at the head and one oxyethylene spacer was found to be the most effective lipid, which showed transfection activity even in presence of high serum levels (50%) greater than Effectene, one of the potent commercially available transfecting agents. Most of these geminis protected plasmid DNA remarkably against DNase I in serum, although the degree of stability was found to vary with their structural features. Conclusions/Significance: -OH groups present on the cationic headgroups in combination with oxyethylene linkers on cholesterol based geminis, gave an optimized combination of new genera of gemini lipids possessing high transfection efficiency even in presence of very high percentage of serum. This property makes them preferential transfection reagents for possible in vivo studies.

Developments in Biotechnology for Environmentally Benign Iron Ore Beneficiation

Biomineralization and biogenesis of iron ore deposits are illustrated in relation to indigenous microorganisms inhabiting iron ore mines. Aerobic and anaerobic microorganisms indigenous to iron oxide mineralization are analyzed. Microbially-induced flotation and flocculation of iron ore minerals such as hematite, alumina, calcite and quartz are discussed with respect to use of four types of microorganisms, namely, Paenibacillus polymyxa, Bacillus subtilis, Saccharomyces cerevisiae and Desulfovibrio desulfuricans. The role of the above organisms in the removal of silica, alumina, clays and apatite from hematite is illustrated with respect to mineral-specific bioreagents, surface chemical changes and microbe-mineral interaction mechanisms. Silica and alumina removal from real iron ores through biobeneficiation is outlined. Environmental benefits of biobeneficiation are demonstrated with respect to biodegradation of toxic reagents and environmentally-safe waste disposal and processing.

Microbially induced selective flotation of sphalerite from galena using mineral-adapted strains of Bacillus megaterium

The selective flotation of sphalerite from a sphalerite-galena mineral mixture has been achieved using cells and extracellular secretions of Bacillus megaterium after adaptation to the chosen minerals. The extracellular secretions obtained after thermolysis of bacterial cells adapted to sphalerite yield the highest flotation recovery of sphalerite with a selectivity index value of 24.5, in comparison to the other cellular and extra-cellular bio-reagents studied. The protein profile for the unadapted and mineral-adapted cells has been found to differ distinctly, attesting to variation in the yield and nature of extra-cellular polymeric substances (EPS). The changes induced in the bacterial cell wall components after adaptation to sphalerite or galena with respect to the contents of phosphate, uronic acid and acetylated sugars of B. megaterium have been quantified. The role of the dissolved metal ions from the minerals as well as that of the constituents of extracellular secretions in modulating the surface charge of the bacterial cells as well as the minerals under study has been confirmed using various enzymatic treatments of the bacterial cells. It has been demonstrated that the induction of additional molecular weight protein fractions as well as the higher amount of extracellular proteins and phosphate secreted after adaptation to sphalerite vis-A-vis galena are contributory factors for the selective separation of sphalerite from galena. (C) 2013 Elsevier B.V. All rights reserved.

Self-assembly of discrete metallamacrocycles employing half-sandwich octahedral diruthenium(II) building units and imidazole-based ligands

Equimolar combination of a series of binuclear half-sandwich p-cymene ruthenium(II) building units Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1a](OTf)(2), Ru-2(mu-eta(4)-N,N'-diphenyloxamidato)( MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1b](OTf)(2) and Ru-2(mu-eta(4)-C6H2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1c](OTf)(2) separately with imidazole-based ditopic ligands (L-1-L-2) in methanol yielded a series of tetranuclear metallamacrocycles 2-7](OTf)(4), respectively L-1 = 1,4-bis(imidazole-1-yl)benzene; L-2 = 4,4'-bis(imidazole-1-yl)biphenyl; OTf- = O3SCF3-]. Similarly, the reaction of Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)2](OTf)(2) 1a](OTf)(2) with a triazine-based tritopic ligand 1,3,5-tris(imidazole-1-yl) triazine (L3) in 3: 2 M ratio afforded an unexpected tetranuclear macrocycle 8](OTf)(4) instead of an expected trigonal prismatic cage 8a](OTf)(6). All the self-assembled macrocycles 2-8](OTf)(4) were isolated in moderate to high yields and were fully characterized by multinuclear H-1, F-19] NMR, IR and electrospray ionization mass spectrometry (ESI-MS). In addition, X-ray diffraction study on the single crystals of 3](OTf)(4) and 8](OTf)(4) also indicated the formation 2 + 2] self-assembled macrocycles. Despite the possibility of formation of different conformational isomeric macrocycles (syn-and anti) and polymeric product due to free rotation of ligand sites of imidazole linkers, the selective formation of single conformational isomer (anti) as the only product is quite interesting. Furthermore, the photo-and electrochemical properties of these assemblies have been studied using UV/Vis absorption and cyclic voltammetry analysis. (c) 2013 Elsevier B.V. All rights reserved.

A cationic cholesterol based nanocarrier for the delivery of p53-EGFP-C3 plasmid to cancer cells

The p53 protein mediated anti-tumor strategy is limited due to the lack of suitable delivery agent with insignificant immunogenic response, serum compatibility, and early and easy detection of the transfected cell population. To overcome these problems, we generated a p53-EGFP-C3 fusion construct which expressed easily detectable green fluorescence protein (GFP) and allowed an estimation of p53 mediated anti-tumor activity. A mixture of cationic cholesterol gemini (Choi-5L) with natural lipid, DOPE (molar ratio 1:4), acronymed as Chol-5LD, formed a nano-liposome as characterized by various physical methods. The prepared clone was evaluated for the expression of GFP and functional p53 in HeLa and two additional cell lines with varied p53 status namely, H1299 (p53(-/-)) and HEK293T (p53(+/+)). Transfected cells were screened using RT-PCR, Western blotting, FACS analysis, MTT, Trypan blue assay and visualized under a fluorescence microscope. The p53-EGFP-C3 fusion protein induced apoptosis in cancer cells as evident from DNA fragmentation, cell cycle analysis, Annexin-V staining and PARP cleavage assays. The transfection and apoptosis induction efficiency of Chol-5LD was significantly higher than commercial reagents Lipofectamine2000 and Effectene irrespective of the cell lines examined. Further it significantly decreases the xenograft tumor volume in nude mice tumors via apoptosis as observed in H&E staining. (C) 2013 Elsevier Ltd. All rights reserved.

Titanium promoted reduction of imines with Grignards, silanes, and zinc: identification of a new mechanism with silanes

Aldimines react with reducing agents, such as Grignards, phenylsilane or zinc in the presence of titanium(IV) isopropoxide to form amines and reductively coupled imines (diamines). Using deuterium labeled reagents, the mechanism of reduction to form amines is described. Reducing agents, such as the Grignard and zinc result in the formation of low valent titanium (LVT), which in turn reduces the imine. On the other hand, phenylsilane reacts by a distinctly different mechanism and where a hydrogen atom from silicon is directly transferred to the titanium coordinated imine. (c) 2014 Elsevier Ltd. All rights reserved.

A Modified Fluorimetric Method for Determination of Hydrogen Peroxide Using Homovanillic Acid Oxidation Principle

Hydrogen peroxide (H2O2) level in biological samples is used as an important index in various studies. Quantification of H2O2 level in tissue fractions in presence of H2O2 metabolizing enzymes may always provide an incorrect result. A modification is proposed for the spectrofluorimetric determination of H2O2 in homovanillic acid (HVA) oxidation method. The modification was included to precipitate biological samples with cold trichloroacetic acid (TCA, 5% w/v) followed by its neutralization with K2HPO4 before the fluorimetric estimation of H2O2 is performed. TCA was used to precipitate the protein portions contained in the tissue fractions. After employing the above modification, it was observed that H2O2 content in tissue samples was >= 2 fold higher than the content observed in unmodified method. Minimum 2 h incubation of samples in reaction mixture was required for completion of the reaction. The stability of the HVA dimer as reaction product was found to be > 12 h. The method was validated by using known concentrations of H2O2 and catalase enzyme that quenches H2O2 as substrate. This method can be used efficiently to determine more accurate tissue H2O2 level without using internal standard and multiple samples can be processed at a time with additional low cost reagents such as TCA and K2HPO4.

Approaches toward (eta(2)-HX) (X = H, SiR (R = Me-3 or Me2Ph), CH3) sigma-complexes of ruthenium

Two new Ru(II)-complexes RuH(Tpms)(PPh3)(2)] 1 (Tpms - (C3H3N2)(3)CSO3, tris-(pyrazolyl) methane sulfonate) and Ru(OTf)(Tpms)(PPh3)(2)] 2 (OTf = CF3SO3) have been synthesized and characterized wherein Ru-H and Ru-OTf are the key reactive centers. Reaction of 1 with HOTf results in the Ru(eta(2)-H-2)(Tpms)(PPh3)(2)]OTf] complex 3, whereas reaction of 1 with Me3SiOTf affords the dihydrogen complex 3 and complex 1 through an unobserved sigma-silane intermediate. In addition, an attempt to characterize the sigma methane complex via reaction of complex 1 with CH3OTf yields complex 2 and free methane. On the other hand, reaction of Ru(OTf)(Tpms)(PPh3)(2)] 2 with H-2 and PhMe2SiH at low temperature resulted in sigma-H-2, 3 and a probable sigma-silane complexes, respectively. However, no sigma-methane complex was observed for the reaction of complex 2 with methane even at low temperature. (C) 2014 Elsevier B. V. All rights reserved.

SELECTIVE ALDEHYDE REDUCTION IN KETOALDEHYDES WITH NaBH4-Na2CO3-H2O AT ROOM TEMPERATURES

A variety of aliphatic and aromatic ketoaldehydes were reduced to the corresponding ketoalcohols with a mixture of sodium borohydride (1.2 equivalents) and sodium carbonate (sixfold molar excess) in water. Reactions were performed at room temperatures over (typically) 2 h, and yields of isolated products generally ranged from 70% to 85%. A biscarbonate-borane complex, (BH3)(2)CO2](2-) 2Na(+), possibly formed from the reagent mixture, is likely the active reductant. The moderated reactivity of this acylborane species would explain the chemoselectivity observed in the reactions. The readily available reagents and the mild aqueous conditions make for ease of operation and environmental compatibility, and make a useful addition to available methodology.

Mitigating UVA light induced reactivity of 6-thioguanine through formation of a Ru(II) half-sandwich complex

The organometallic complex of (eta(6)-cymene)Ru(II)Br with 6-thioguanine (6-TG) shows better photostability than the biologically active 6-thioguanine which is used as an immunosuppressant and as an anticancer agent.