11 research outputs found
Photophysics of cage/guest assemblies : photoinduced electron transfer between a coordination cage containing osmium(II) luminophores, and electron-deficient bound guests in the central cavity
An octanuclear cubic Os4Zn4 coordination cage, containing Os(II) tris-diimine units at four of the eight vertices which are good photoelectron donors from their 3MLCT excited state, performs photoinduced electron transfer to electron-accepting organic guests which bind in the central cavity in water via the hydrophobic effect: the resulting charge-separated states have lifetimes of ca. 200 ps and have been characterized by transient absorption spectroscopy
Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.
BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden
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Solvent-dependent modulation of metal–metal electronic interactions in a dinuclear cyanoruthenate complex: a detailed electrochemical, spectroscopic and computational study
The dinuclear complex [{Ru(CN)4}2(μ-bppz)]4− shows a strongly solvent-dependent metal–metal
electronic interaction which allows the mixed-valence state to be switched from class 2 to class 3 by
changing solvent from water to CH2Cl2. In CH2Cl2 the separation between the successive Ru(II)/Ru(III)
redox couples is 350 mVand the IVCT band (from the UV/Vis/NIR spectroelectrochemistry) is
characteristic of a borderline class II/III or class III mixed valence state. In water, the redox separation is
only 110 mVand the much broader IVCT transition is characteristic of a class II mixed-valence state.
This is consistent with the observation that raising and lowering the energy of the d(π) orbitals in CH2Cl2
or water, respectively, will decrease or increase the energy gap to the LUMO of the bppz bridging ligand,
which provides the delocalisation pathway via electron-transfer. IR spectroelectrochemistry could only be
carried out successfully in CH2Cl2 and revealed class III mixed-valence behaviour on the fast IR
timescale. In contrast to this, time-resolved IR spectroscopy showed that the MLCTexcited state, which is
formulated as RuIII(bppz˙−)RuII and can therefore be considered as a mixed-valence Ru(II)/Ru(III)
complex with an intermediate bridging radical anion ligand, is localised on the IR timescale with
spectroscopically distinct Ru(II) and Ru(III) termini. This is because the necessary electron-transfer via the
bppz ligand is more difficult because of the additional electron on bppz˙− which raises the orbital through
which electron exchange occurs in energy. DFT calculations reproduce the electronic spectra of the
complex in all three Ru(II)/Ru(II), Ru(II)/Ru(III) and Ru(III)/Ru(III) calculations in both water and CH2Cl2
well as long as an explicit allowance is made for the presence of water molecules hydrogen-bonded to the
cyanides in the model used. They also reproduce the excited-state IR spectra of both [Ru(CN)4(μ-bppz)]2–
and [{Ru(CN)4}2(μ-bppz)]4− very well in both solvents. The reorganization of the water solvent shell
indicates a possible dynamical reason for the longer life time of the triplet state in water compared to
CH2Cl2
Catalysis in a Cationic Coordination Cage Using a Cavity-Bound Guest and Surface-Bound Anions: Inhibition, Activation, and Autocatalysis
The
Kemp elimination (reaction of benzisoxazole with
base to give 2-cyanophenolate) is catalyzed in the cavity of a cubic
M<sub>8</sub>L<sub>12</sub> coordination cage because of a combination
of (i) benzisoxazole binding in the cage cavity driven
by the hydrophobic effect, and (ii) accumulation of hydroxide ions
around the 16+ cage surface driven by ion-pairing. Here we show how
reaction of the cavity-bound guest is modified by the presence of
other anions which can also accumulate around the cage surface and
displace hydroxide, inhibiting catalysis of the cage-based reaction.
Addition of chloride or fluoride inhibits the reaction with hydroxide
to the extent that a new autocatalytic pathway becomes apparent, resulting
in a sigmoidal reaction profile. In this pathway the product 2-cyanophenolate
itself accumulates around the cationic cage surface, acting as the
base for the next reaction cycle. The affinity of different anions
for the cage surface is therefore 2-cyanophenolate (generating autocatalysis)
> chloride > fluoride (which both inhibit the reaction with
hydroxide
but cannot deprotonate the benzisoxazole guest) > hydroxide
(default reaction pathway). The presence of this autocatalytic pathway
demonstrates that a reaction of a cavity-bound guest can be induced
with different anions around the cage surface in a controllable way;
this was confirmed by adding different phenolates to the reaction,
which accelerate the Kemp elimination to different extents depending
on their basicity. This represents a significant step toward the goal
of using the cage as a catalyst for bimolecular reactions between
a cavity-bound guest and anions accumulated around the surface
Catalysis in a Cationic Coordination Cage Using a Cavity-Bound Guest and Surface-Bound Anions: Inhibition, Activation, and Autocatalysis
The
Kemp elimination (reaction of benzisoxazole with
base to give 2-cyanophenolate) is catalyzed in the cavity of a cubic
M<sub>8</sub>L<sub>12</sub> coordination cage because of a combination
of (i) benzisoxazole binding in the cage cavity driven
by the hydrophobic effect, and (ii) accumulation of hydroxide ions
around the 16+ cage surface driven by ion-pairing. Here we show how
reaction of the cavity-bound guest is modified by the presence of
other anions which can also accumulate around the cage surface and
displace hydroxide, inhibiting catalysis of the cage-based reaction.
Addition of chloride or fluoride inhibits the reaction with hydroxide
to the extent that a new autocatalytic pathway becomes apparent, resulting
in a sigmoidal reaction profile. In this pathway the product 2-cyanophenolate
itself accumulates around the cationic cage surface, acting as the
base for the next reaction cycle. The affinity of different anions
for the cage surface is therefore 2-cyanophenolate (generating autocatalysis)
> chloride > fluoride (which both inhibit the reaction with
hydroxide
but cannot deprotonate the benzisoxazole guest) > hydroxide
(default reaction pathway). The presence of this autocatalytic pathway
demonstrates that a reaction of a cavity-bound guest can be induced
with different anions around the cage surface in a controllable way;
this was confirmed by adding different phenolates to the reaction,
which accelerate the Kemp elimination to different extents depending
on their basicity. This represents a significant step toward the goal
of using the cage as a catalyst for bimolecular reactions between
a cavity-bound guest and anions accumulated around the surface
Catalysis in a Cationic Coordination Cage Using a Cavity-Bound Guest and Surface-Bound Anions: Inhibition, Activation, and Autocatalysis
The
Kemp elimination (reaction of benzisoxazole with
base to give 2-cyanophenolate) is catalyzed in the cavity of a cubic
M<sub>8</sub>L<sub>12</sub> coordination cage because of a combination
of (i) benzisoxazole binding in the cage cavity driven
by the hydrophobic effect, and (ii) accumulation of hydroxide ions
around the 16+ cage surface driven by ion-pairing. Here we show how
reaction of the cavity-bound guest is modified by the presence of
other anions which can also accumulate around the cage surface and
displace hydroxide, inhibiting catalysis of the cage-based reaction.
Addition of chloride or fluoride inhibits the reaction with hydroxide
to the extent that a new autocatalytic pathway becomes apparent, resulting
in a sigmoidal reaction profile. In this pathway the product 2-cyanophenolate
itself accumulates around the cationic cage surface, acting as the
base for the next reaction cycle. The affinity of different anions
for the cage surface is therefore 2-cyanophenolate (generating autocatalysis)
> chloride > fluoride (which both inhibit the reaction with
hydroxide
but cannot deprotonate the benzisoxazole guest) > hydroxide
(default reaction pathway). The presence of this autocatalytic pathway
demonstrates that a reaction of a cavity-bound guest can be induced
with different anions around the cage surface in a controllable way;
this was confirmed by adding different phenolates to the reaction,
which accelerate the Kemp elimination to different extents depending
on their basicity. This represents a significant step toward the goal
of using the cage as a catalyst for bimolecular reactions between
a cavity-bound guest and anions accumulated around the surface