A study of the interaction between inverted cucurbit[7]uril and symmetric viologens

The interaction between inverted cucuribit[7]uril (iQ[7]) and a series of symmetric viologen derivatives bearing aliphatic substituents of variable length, namely dicationic dialkyl-4,4′-bipyridinium guests where the alkyl is CH₃(CH₂)n with n = 0 to 6, has been studied in aqueous solution by ¹H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. In the case of both n = 5 (HV ²⁺) and 6 (SV²⁺), single crystal X-ray diffraction revealed the composition to be [(iQ[7])₂(HV)₂][CdCl₃Br][H₃O+]₂[H₂O]₁₂.₅ and (iQ[7])₂(C7-SV)₁.₅[CdCl₄]₄(H₃O⁺)₅(H₂O)₈, respectively, with both adopting an external B-type structure (the alkyl chains of the viologen reside within the iQ[7])

Membrane electrochemical reactors (MER) for NADH regeneration in HLADH-catalysed synthesis: comparison of effectiveness

Two membrane electrochemical reactors(MER) were designed and applied to HLADH-catalysed reduction of cyclohexanone to cyclohexanol. The regeneration of the cofactor NADH was ensured electrochemically, using either methyl viologen or a rhodium complex as electrochemical mediator. A semipermeable membrane (dialysis or ultra-filtration) was integrated in the filter-press electrochemical reactor to confine the enzyme(s) as close as possible to the electrode surface. When methyl viologen was used, the transformation ratio of cyclohexanone varied from 0 to 65% depending on the internal arrangement of the reactor. Matching the reactor configuration to the reaction system was essential in this case. With the rhodium complex, the ultra-filtration MER was tested in continuous and recycling configurations. The best conditions led to 100% transformation of 0.1 L volume of 0.1 M cyclohexanone after 70 h with the recycling mode. Finally, the performances of the reactors are discussed with respect to different evaluations of the production yields

Reversible intercalation of methyl viologen as a dicationic charge carrier in aqueous batteries.

The interactions between charge carriers and electrode structures represent one of the most important considerations in the search for new energy storage devices. Currently, ionic bonding dominates the battery chemistry. Here we report the reversible insertion of a large molecular dication, methyl viologen, into the crystal structure of an aromatic solid electrode, 3,4,9,10-perylenetetracarboxylic dianhydride. This is the largest insertion charge carrier when non-solvated ever reported for batteries; surprisingly, the kinetic properties of the (de)insertion of methyl viologen are excellent with 60% of capacity retained when the current rate is increased from 100 mA g-1 to 2000 mA g-1. Characterization reveals that the insertion of methyl viologen causes phase transformation of the organic host, and embodies guest-host chemical bonding. First-principles density functional theory calculations suggest strong guest-host interaction beyond the pure ionic bonding, where a large extent of covalency may exist. This study extends the boundary of battery chemistry to large molecular ions as charge carriers and also highlights the electrochemical assembly of a supramolecular system

Selective superoxide generation within mitochondria by the targeted redox cycler MitoParaquat

Superoxide is the proximal reactive oxygen species (ROS) produced by the mitochondrial respiratory chain and plays a major role in pathological oxidative stress and redox signaling. While there are tools to detect or decrease mitochondrial superoxide, none can rapidly and specifically increase superoxide production within the mitochondrial matrix. This lack impedes progress, making it challenging to assess accurately the roles of mitochondrial superoxide in cells and in vivo. To address this unmet need, we synthesized and characterized a mitochondria-targeted redox cycler, MitoParaquat (MitoPQ) that comprises a triphenylphosphonium lipophilic cation conjugated to the redox cycler paraquat. MitoPQ accumulates selectively in the mitochondrial matrix driven by the membrane potential. Within the matrix, MitoPQ produces superoxide by redox cycling at the flavin site of complex I, selectively increasing superoxide production within mitochondria. MitoPQ increased mitochondrial superoxide in isolated mitochondria and cells in culture ~a thousand-fold more effectively than untargeted paraquat. MitoPQ was also more toxic than paraquat in the isolated perfused heart and in Drosophila in vivo. MitoPQ enables the selective generation of superoxide within mitochondria and is a useful tool to investigate the many roles of mitochondrial superoxide in pathology and redox signaling in cells and in vivo

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Department of Chemical EngineeringUtilizing carbon dioxide to valuable chemicals is attractive technology for reducing CO2 emission. Among the chemicals converted from CO2, formic acid is one of the most valuable chemicals. Efficient conversion of CO2 to formic acid by electro-biocatalytic system was reported without expensive cofactor and noble metals. In this study, Shewanella oneidensis MR-1 (S. oneidensis MR-1) and encapsulated Formate dehydrogenase1 from Methylobacterium extorquens AM1 (MeFDH1) were applied to electro-biocatalytic reaction as a whole cell and encapsulated biocatalyst, respectively. First, S. oneidensis MR-1, when aerobically grown in Luria-Bertani (LB) medium, exhibited its ability for the conversion of CO2 into formic acid with productivity of 0.59 mM???hr-1 for 24 hr. In addition, CO2 reduction reaction catalyzed by S. oneidensis MR-1, when anaerobically grown in newly optimized LB medium supplemented with fumarate and nitrate, exhibited 3.2-fold higher productivity (1.9 mM???hr-1 for 72 hr). Second, previous study has demonstrated that electro-biocatalytic conversion of CO2 to formic acid by engineered MeFDH1 shows higher productivity than wild type. To increase physical strength, stability, reusability of MeFDH1, MeFDH1 was encapsulated in pure alginate and alginate silica hybrid beads. Michaelis-Menten kinetic constants demonstrated that binding affinity and maximum reaction rate of both encapsulated MeFDH1 were declined. Compared with pure alginate beads (5.4%), alginate-silica hybrid beads (67.4%) exhibited more higher recycling productivity after 4 cycles. These results show that the immobilization of MeFDH1 through encapsulation of by alginate-silica hybrid is a more suitable method to recycle formate production and prevent leakage of MeFDH1.ope

Rational Design of Pore Size and Functionality in a Series of Isoreticular Zwitterionic Metal-Organic Frameworks

The isoreticular expansion and functionalization of charged-polarized porosity has been systematically explored by the rational design of 11 isostructural zwitterionic metal-organic frameworks (ZW-MOFs). This extended series of general structural composition {[M3F(L1)3(L2)1.5]·guests}n was prepared by employing the solvothermal reaction of Co and Ni tetrafluoroborates with a binary ligand system composed of zwitterionic pyridinium derivatives and traditional functionalized ditopic carboxylate auxiliary ligands (HL1·Cl = 1-(4-carboxyphenyl)-4,4′-bipyridinium chloride, Hcpb·Cl; or 1-(4-carboxyphenyl-3-hydroxyphenyl)-4,4′-bipyridinium chloride, Hchpb·Cl; and H2L2 = benzene-1,4-dicarboxylic acid, H2bdc; 2-aminobenzene-1,4-dicarboxylic acid, H2abdc; 2,5-dihydroxy-1,4-benzenedicarboxylic acid, H2dhbdc; biphenyl-4,4′-dicarboxylic acid, H2bpdc; or stilbene-4,4′-dicarboxylic acid, H2sdc). Single-crystal structure analyses revealed cubic crystal symmetry (I-43m, a = 31-36 Å) with a 3D pore system of significant void space (73-81%). The pore system features three types of pores being systematically tunable in size ranging from 17.4 to 18.8 Å (pore I), 8.2 to 12.8 Å (pore II), and 4.8 to 10.4 Å (pore III) by the choice of auxiliary ligands. All members of this series have noninterpenetrating structures and exhibit robust architectures, as evidenced by their permanent porosity and high thermal stability (up to 300 °C). The structural integrity and specific surface areas could be systematically optimized using supercritical CO2 exchange methods for framework activation resulting in BET surface areas ranging from 1250 to 2250 m2/g. Most interestingly, as a structural landmark, we found the pore surfaces lined with charge gradients employed by the pyridinium ligands. This key feature results in significant adsorption of carbon dioxide and methane which is attributed to polarization effects. With this contribution we pioneer the reticulation of pyridinium building blocks into extended zwitterionic networks in which specific properties can be targeted