A self-powered "sense-act-treat" system that is based on a biofuel cell and controlled by boolean logic

Bio-logic-al: an autonomous, integrated "sense-act-treat" system that is based on an enzymatic biofuel cell has been developed. The system couples a biocomputing logic-detection method with a drug-release system to provide a logic-activated therapeutic intervention in response to a simulated abnormal physiological state, without the need for an external power source, control electronics, or microelectromechanical actuators.     

Complexation behavior of trivalent actinides and lanthanides with 1,10-phenanthroline-2,9-dicarboxylic acid based ligands: insight from density functional theory

We have investigated the complexation behavior of preorganized 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) based ligands with trivalent lanthanides and actinides using density functional theory with various GGA type exchange-correlation functionals and different basis sets. New ligands have been designed from PDA through functionalization with soft donor atoms such as sulfur, resulting in mono-thio-dicarboxylic acids (TCA/TCA1) and di-thio-dicarboxylic acid (THIO). It has been found that selectivity in terms of complexation energy of actinides over lanthanides is the maximum with TCA1 where the metal-ligand binding is through the O atoms. This unusual feature where a softer actinide metal ion is bonded strongly with hard donor oxygen atoms has been explained using the popular chemical concepts, viz., Pearson's Hard-Soft-Acid-Base (HSAB) principle and the frontier orbital theory of chemical reactivity as proposed by Fukui. Detailed analysis within the framework of the HSAB principle indicates that the presence of softer nitrogen atoms in the phenanthroline moiety (which also act as donors to the metal ion) has a profound influence in changing the soft nature of the actinide ion, which in turn binds with the hard oxygen atoms in a stronger way as compared to the valence isoelectronic lanthanide ion. Also, the trends in the variation of calculated values of the metal-ligand bond distances and the corresponding complex formation energies have been rationalized using the Fukui reactivity indices corresponding to the metal ions and the donor sites. All the calculations have also been done in the presence of solvent. The "intra-ligand synergistic effect" demonstrated here for PDA or TCA1 with soft and hard donor centers might be very important in designing new ligands for selective extraction of various metal ions in a competitive environment. However, for TCA and THIO ligands with only soft donor centers, "intra-ligand synergism" may not be very efficient although reports are available demonstrating soft-soft inter-ligand synergism. Nevertheless, in the case of TCA and THIO complexes, a shorter Am-S bond distance in conjunction with lower metal ion charge and a higher percentage of orbital interaction energy corroborate the presence of a higher degree of covalency in Am-S bonds, which in turn may be responsible for selectivity towards Am(3+).     

Dioxygen Reactivity of Biomimetic Iron-Catecholate and Iron-o-Aminophenolate Complexes of a Tris(2-pyridylthio)methanido Ligand: Aromatic CC Bond Cleavage of Catecholate versus o-Iminobenzosemiquinonate Radical Formation

An iron(III)-catecholate complex [L(1) Fe(III) (DBC)] (2) and an iron(II)-o-aminophenolate complex [L(1) Fe(II) (HAP)] (3; where L(1) =tris(2-pyridylthio)methanido anion, DBC=dianionic 3,5-di-tert-butylcatecholate, and HAP=monoanionic 4,6-di-tert-butyl-2-aminophenolate) have been synthesised from an iron(II)-acetonitrile complex [L(1) Fe(II) (CH(3) CN)(2) ](ClO(4) ) (1). Complex 2 reacts with dioxygen to oxidatively cleave the aromatic C?C bond of DBC giving rise to selective extradiol cleavage products. Controlled chemical or electrochemical oxidation of 2, on the other hand, forms an iron(III)-semiquinone radical complex [L(1) Fe(III) (SQ)](PF(6) ) (2(ox) -PF(6) ; SQ=3,5-di-tert-butylsemiquinonate). The iron(II)-o-aminophenolate complex (3) reacts with dioxygen to afford an iron(III)-o-iminosemiquinonato radical complex [L(1) Fe(III) (ISQ)](ClO(4) ) (3(ox) -ClO(4) ; ISQ=4,6-di-tert-butyl-o-iminobenzosemiquinonato radical) via an iron(III)-o-amidophenolate intermediate species. Structural characterisations of 1, 2, 2(ox) and 3(ox) reveal the presence of a strong iron?carbon bonding interaction in all the complexes. The bond parameters of 2(ox) and 3(ox) clearly establish the radical nature of catecholate- and o-aminophenolate-derived ligand, respectively. The effect of iron?carbon bonding interaction on the dioxygen reactivity of biomimetic iron-catecholate and iron-o-aminophenolate complexes is discussed.     

Correspondence of Ru(III) Ru(II) and Ru(IV) Ru(III) mixed valent states in a small dinuclear complex

The diruthenium(III) compound [(μ-oxa){Ru(acac)(2)}(2)] [1, oxa(2-) =oxamidato(2-), acac(-) =2,4-pentanedionato] exhibits an S=1 ground state with antiferromagnetic spin-spin coupling (J=-40 cm(-1)). The molecular structure in the crystal of 1?2 C(7)H(8) revealed an intramolecular metal-metal distance of 5.433 ? and a notable asymmetry within the bridging ligand. Cyclic voltammetry and spectroelectrochemistry (EPR, UV/Vis/NIR) of the two-step reduction and of the two-step oxidation (irreversible second step) produced monocation and monoanion intermediates (K(c) =10(5.9)) with broad NIR absorption bands (ε ca. 2000 M(-1)cm(-1)) and maxima at 1800 (1(-)) and 1500 nm (1(+)). TD-DFT calculations support a Ru(III)Ru(II) formulation for 1(-) with a doublet ground state. The 1(+) ion (Ru(IV)Ru(III)) was calculated with an S=3/2 ground state and the doublet state higher in energy (ΔE=694.6 cm(-1)). The Mulliken spin density calculations showed little participation of the ligand bridge in the spin accommodation for all paramagnetic species [(μ-oxa){Ru(acac)(2)}(2)](n), n=+1, 0, -1, and, accordingly, the NIR absorptions were identified as metal-to-metal (intervalence) charge transfers. Whereas only one such NIR band was observed for the Ru(III)Ru(II) (4d(5)/4d(6)) system 1(-), the Ru(IV)Ru(III) (4d(4)/4d(5)) form 1(+) exhibited extended absorbance over the UV/Vis/NIR range.     

Rheological signatures of ethylene methyl acrylate‐multiwalled carbon nanotube nanocomposites

The rheological behavior of nanocomposites based on multiwalled carbon nanotube (MWNT) with three commercial grades of ethylene methyl acrylate (EMA) copolymers containing 9, 24, and 30 wt% methyl acrylate (MA) was investigated under dynamic and steady shear flow (in a capillary) conditions. Storage modulus (in dynamic shear) value increases especially at higher frequency levels due to increased polymer‐filler interactions. Both the unfilled and filled composites exhibit rheological behavior of non‐Newtonian fluids. In both steady shear and capillary flow, the nanocomposites register a slightly higher viscosity than neat EMAs, with dependence on the MWNTs content. All systems with various loading of MWNTs represent an increase in elastic response with increasing frequency. The die swell decreases with the MWNTs loading. Dynamic and steady shear rheological properties register a good correlation in regard to the viscous versus elastic response of such systems inline with the Cox–Merz concept. Increased MA content leads to inferior dispersion of MWNTs in EMA matrix. Morphological studies exhibit that MWNTs become more aligned along longitudinal direction after extrusion leading to improved dispersion. Copyright © 2010 John Wiley & Sons, Ltd.     

Hybrid porous tin(IV) phosphonate: an efficient catalyst for adipic acid synthesis and a very good adsorbent for CO2 uptake

A new porous organic-inorganic hybrid tin phosphonate material has been synthesized hydrothermally, which shows a Brunauer-Emmett-Teller surface area of 723 m(2) g(-1) and it adsorbs 4.8 mmol g(-1) CO(2) at 273 K and 5 bar pressure. The material also shows remarkable catalytic activity in one-pot liquid phase oxidation of cyclohexanone to adipic acid under eco-friendly conditions.     

Porphyrin based porous organic polymers: novel synthetic strategy and exceptionally high CO2 adsorption capacity

Iron containing porous organic polymers (Fe-POPs) have been synthesized by a facile one-pot bottom-up approach to porphyrin chemistry by an extended aromatic substitution reaction between pyrrole and aromatic dialdehydes in the presence of small amount of Fe(III). The Fe-POPs possess very high BET surface area, large micropores and showed excellent CO(2) capture (~19 wt%) at 273 K/1 bar.     

A new colorimetric chemodosimeter for mercury ion via specific thioacetal deprotection in aqueous solution and living cells

A sensitive and selective new chemodosimeteric chemosensor (DIBT) for mercury ions was successfully devised and characterized. Upon addition of Hg²⁺ to DIBT, a red-edge absorption band at 972 nm was observed. An important feature for the new chemodosimeter is its high selectivity toward mercury ions over the other competitive species due to Hg²⁺-triggered specific C–S cleavage, making the ‘naked-eye’ detection of mercury ions possible in aqueous solution and living cells such as Candida albicans.     

Semiempirical quantum mechanical calculations of dipolar interaction between dipyridamole and dipalmitoyl phosphatidyl choline in Langmuir monolayers

Recent studies have shown that dipalmitoyl phosphatidyl choline (DPPC) monolayers respond cooperatively to the presence of dipyridamole (DIP) guest molecules even at small concentrations, which is a signature of molecular recognition. Using semiempirical quantum mechanical calculations for the DIP-DPPC system, we show that the incorporation of DIP causes large changes in the vertical dipole moment of the DIP-DPPC system, which can explain why measurable changes in surface potential are observed experimentally even at very low DIP concentrations. The calculations are also consistent with the anomalous concentration dependence of the surface pressure and surface potential isotherms for DIP-DPPC monolayers. Rather than saturation or a continuous increase in the effects caused by the incorporation of increasing amounts of DIP, the experimentally observed inversion in the behavior of the surface potential as the DIP concentration reaches 0.5 mol % would be caused by a change in DIP conformation, from a vertical arrangement for the DIP rings to a horizontal or intermediate arrangement. The strong dipolar interactions indicated in the calculations may also be the origin of the drastic changes in monolayer morphology seen in fluorescence microscopy images, with triskellion-shaped domains being formed for condensed DIP-DPPC monolayers.