Photocatalytic redox reactions at the surface of liposomes

Current energy-sources in the form of fossil fuels are quickly being depleted, while the demand of energy by society is increasing. In order to sustain this growth in energy demand, alternatives for the production of energy in a usable form are needed. One of such alternatives is to employ photocatalysis in order to use sunlight for the production of chemical fuels such as for example H2 or methanol. For the production of fuels, electrons are required that can be obtained by oxidizing water, as done by nature in a process called photosynthesis. The work in this thesis was inspired by this natural process; photosensitizers and water-oxidation catalysts were bound to lipid bilayers and their ability to photocatalytically oxidize water was studied in different conditions. The anchoring of compounds to a lipid bilayer leads to large differences in reactivity compared to homogeneous systems. In some cases, even the mechanism of the photocatalytic reaction changed upon membrane-anchoring of the constituents. In general, detailed experiments are described that fully characterize photocatalytic systems, because the mechanism of a reaction involving two different catalytic species is not straight-forward, and cannot be described by a single set of turn-over numbers.NRSC-Catalysi

Tetrahedral zinc in tetrakis(1-methyl-1H-imidazole-kappa N-3)zinc bis(tetrafluoridoborate)

Peer reviewe

Charge-state dependent vibrational relaxation in a single-molecule junction

The interplay between nuclear and electronic degrees of freedom strongly influences molecular charge transport. Herein, we report on transport through a porphyrin dimer molecule, weakly coupled to graphene electrodes, that displays sequential tunneling within the Coulomb-blockade regime. The sequential transport is initiated by current-induced phonon absorption and proceeds by rapid sequential transport via a non-equilibrium vibrational distribution. We demonstrate this is possible only when the vibrational dissipation is slow relative to sequential tunneling rates, and obtain a lower bound for the vibrational relaxation time of 8 ns, a value that is dependent on the molecular charge state.Comment: 8 pages, 7 figure

Long-lived charged states of single porphyrin-tape junctions under ambient conditions

The ability to control the charge state of individual molecules wired in two-terminal single-molecule junctions is a key challenge in molecular electronics, particularly in relation to the development of molecular memory and other computational componentry. Here we demonstrate that single porphyrin molecular junctions can be reversibly charged and discharged at elevated biases under ambient conditions due to the presence of a localised molecular eigenstate close to the Fermi edge of the electrodes. In particular, we can observe long-lived charge-states with lifetimes upwards of 1–10 seconds after returning to low bias and large changes in conductance, in excess of 100-fold at low bias. Our theoretical analysis finds charge-state lifetimes within the same time range as the experiments. The ambient operation demonstrates that special conditions such as low temperatures or ultra-high vacuum are not essential to observe hysteresis and stable charged molecular junctions

Bias-driven conductance increase with length in porphyrin tapes

A key goal in molecular electronics has been to find molecules that facilitate efficient charge transport over long distances. Normally molecular wires become less conductive with increasing length. Here we report a series of fused porphyrin oligomers for which the conductance increases substantially with length by > 10-fold at a bias of 0.7 V. This exceptional behavior can be attributed to the rapid decrease of the HOMO-LUMO gap with the length of fused porphyrins. In contrast, for butadiyne-linked porphyrin oligomers with moderate inter-ring coupling, a normal conductance decrease with length is found for all bias voltages explored (± 1 V), although the attenuation factor (β) decreases from ca. 2 nm-1 at low bias to < 1 nm-1 at 0.9 V, highlighting that β is not an intrinsic molecular property. Further theoretical analysis using density functional theory underlines the role of inter-site coupling and indicates that this large increase in conductance with length at increasing voltages can be generalized to other molecular oligomers

Reduced costs with bisoprolol treatment for heart failure - An economic analysis of the second Cardiac Insufficiency Bisoprolol Study (CIBIS-II)

Background Beta-blockers, used as an adjunctive to diuretics, digoxin and angiotensin converting enzyme inhibitors, improve survival in chronic heart failure. We report a prospectively planned economic analysis of the cost of adjunctive beta-blocker therapy in the second Cardiac Insufficiency BIsoprolol Study (CIBIS II). Methods Resource utilization data (drug therapy, number of hospital admissions, length of hospital stay, ward type) were collected prospectively in all patients in CIBIS . These data were used to determine the additional direct costs incurred, and savings made, with bisoprolol therapy. As well as the cost of the drug, additional costs related to bisoprolol therapy were added to cover the supervision of treatment initiation and titration (four outpatient clinic/office visits). Per them (hospital bed day) costings were carried out for France, Germany and the U.K. Diagnosis related group costings were performed for France and the U.K. Our analyses took the perspective of a third party payer in France and Germany and the National Health Service in the U.K. Results Overall, fewer patients were hospitalized in the bisoprolol group, there were fewer hospital admissions perpatient hospitalized, fewer hospital admissions overall, fewer days spent in hospital and fewer days spent in the most expensive type of ward. As a consequence the cost of care in the bisoprolol group was 5-10% less in all three countries, in the per them analysis, even taking into account the cost of bisoprolol and the extra initiation/up-titration visits. The cost per patient treated in the placebo and bisoprolol groups was FF35 009 vs FF31 762 in France, DM11 563 vs DM10 784 in Germany and pound 4987 vs pound 4722 in the U.K. The diagnosis related group analysis gave similar results. Interpretation Not only did bisoprolol increase survival and reduce hospital admissions in CIBIS II, it also cut the cost of care in so doing. This `win-win' situation of positive health benefits associated with cost savings is Favourable from the point of view of both the patient and health care systems. These findings add further support for the use of beta-blockers in chronic heart failure

Decoding key transient inter-catalyst interactions in a metallaphotoredox-catalysed cross-electrophile coupling reaction

Metallaphotoredox chemistry has recently witnessed a renaissance through the use of abundant first-row transition metals combined with suitable photocatalysts. The intricate details arising from the combination of two (or more) catalytic components during the reaction and specially the inter-catalyst interactions remain poorly understood. As a representative example of a catalytic process featuring such intricacies, we here present a meticulous study of the mechanism of a cobalt-organophotoredox catalysed allylation of aldehydes. Importantly, the commonly proposed elementary steps in reductive metallaphotoredox chemistry are more complex than previously assumed. After initial reductive quenching, a transient charge-transfer complex forms that interacts with both the transition-metal catalyst, as well as the catalytic base. Surprisingly, the former interaction leads to deactivation due to induced charge recombination, while the latter promotes deprotonation of the electron donor, which is a crucial step in order to promote productive catalysis, but is often neglected. Due to the low efficiency of this process, the overall catalytic reaction is photon-limited and the cobalt catalyst remains in a dual resting state awaiting photoinduced reduction. These new insights are of general importance to the synthetic community, as photoredox chemistry has become a powerful tool used in the creation of elusive compounds through carbon-carbon bond formations. Understanding the underlying factors that determine the efficiency of such reactions provides a conceptually stronger reactivity paradigm to empower future approaches to synthetic challenges that rely on dual metallaphotoredox catalysis

Asymmetric Synthesis of Homoallylic Alcohols Featuring Vicinal Tetrasubstituted Carbon Centers via Dual Pd/Photoredox Catalysis

Dual palladium/photoredox-catalysis provides an effective method for the asymmetric synthesis of vicinal a,b-tri/tetra- or a,b-tetra-substituted homoallylic alcohols. Regio- and enantioselective decarboxylative allylic alkylation of vinyl cyclic carbonates is reported using Hantzsch type esters as radical precursors. The developed methodology combines the use of versatile and accessible reagents and can be operated under mild reaction conditions giving the target molecules in appreciable to good yields, high branch-selectivity and appreciable enantiomeric ratios of up to 94:6. This protocol marks a rare example of the use of prochiral electrophiles for the creation of vicinal congested carbon centers