Magnetic exchange interactions in symmetric lanthanide dimetallics

Multi-frequency EPR spectra and CASSCF-SO calculations on two symmetric homo-dimetallic lanthanide complexes are used to determine the magnetic exchange coupling in the low-lying states.

Accessing γ-Ga2S3 by solventless thermolysis of gallium xanthates: a low-temperature limit for crystalline products

Alkyl-xanthato gallium(iii) complexes of the form [Ga(S₂COR)₃], where R = Me (1), Et (2), ⁱPr (3), ⁿPr (4), ⁿBu (5), ^sBu (6) and ⁱBu (7), have been synthesized and fully characterised. The crystal structures for 1 and 3-7 have been solved and examined to elucidate if these structures are related to their decomposition. Thermogravimetric analysis was used to gain insight into the decomposition temperatures for each complex. Unlike previously explored metal xanthate complexes which break down at low temperatures (<250 °C), to form crystalline metal chalcogenides, powder X-ray diffraction measurements suggest that when R ≥ Et these complexes did not produce crystalline gallium sulfides until heated to 500 °C, where γ-Ga₂S₃ was the sole product formed. In the case of R = Me, Chugaev elimination did not occur and amorphous Ga_xS_y products were formed. We conclude therefore that the low-temperature synthesis route offered by the thermal decomposition of metal xanthate precursors, which has been reported for many metal sulfide systems prior to this, may not be appropriate in the case of gallium sulfides.

Correlating blocking temperatures with relaxation mechanisms in monometallic single-molecule magnets with high energy barriers (Ueff > 600 K)

Correlating blocking temperatures with relaxation mechanisms in single-molecule magnets.

A large barrier single-molecule magnet without magnetic memory

We report a six coordinate Dy^III single-molecule magnet (SMM) with an energy barrier of 1110 K for thermal relaxation of magnetization, but no magnetic hysteresis above 2 K.

The effects of remote ischaemic preconditioning on coronary artery function in patients with stable coronary artery disease

Background

Remote ischaemic preconditioning (RIPC) is a cardioprotective intervention invoking intermittent periods of ischaemia in a tissue or organ remote from the heart. The mechanisms of this effect are incompletely understood. We hypothesised that RIPC might enhance coronary vasodilatation by an endothelium-dependent mechanism.

Methods

We performed a prospective, randomised, sham-controlled, blinded clinical trial. Patients with stable coronary artery disease (CAD) undergoing elective invasive management were prospectively enrolled, and randomised to RIPC or sham (1:1) prior to angiography. Endothelial-dependent vasodilator function was assessed in a non-target coronary artery with intracoronary infusion of incremental acetylcholine doses (10^− 6, 10^− 5, 10^− 4 mol/l). Venous blood was sampled pre- and post-RIPC or sham, and analysed for circulating markers of endothelial function. Coronary luminal diameter was assessed by quantitative coronary angiography. The primary outcome was the between-group difference in the mean percentage change in coronary luminal diameter following the maximal acetylcholine dose (Clinicaltrials.gov identifier: NCT02666235).

Results

75 patients were enrolled. Following angiography, 60 patients (mean ± SD age 57.5 ± 8.5 years; 80% male) were eligible and completed the protocol (n = 30 RIPC, n = 30 sham). The mean percentage change in coronary luminal diameter was − 13.3 ± 22.3% and − 2.0 ± 17.2% in the sham and RIPC groups respectively (difference 11.32%, 95%CI: 1.2– 21.4, p = 0.032). This remained significant when age and sex were included as covariates (difference 11.01%, 95%CI: 1.01– 21.0, p = 0.035). There were no between-group differences in endothelial-independent vasodilation, ECG parameters or circulating markers of endothelial function.

Conclusions

RIPC attenuates the extent of vasoconstriction induced by intracoronary acetylcholine infusion. This endothelium-dependent mechanism may contribute to the cardioprotective effects of RIPC.

A sub-Kelvin cryogen-free EPR system

We present an EPR instrument built for operation at Q band below 1K. Our cryogen-free Dewar integrates with a commercial electro-magnet and bridge. A description of the cryogenic and RF systems is given, along with the adaptations to the standard EPR experiment for operation at sub-Kelvin temperatures. As a first experiment, the EPR spectra of powdered Cr₁₂O₉(OH)₃ [Formula: see text] were measured. The sub-Kelvin EPR spectra agree well with predictions, and the performance of the sub-Kelvin system at 5K is compared to that of a commercial spectrometer.

Redox-State Dependent Spectroscopic Properties of Porous Organic Polymers Containing Furan, Thiophene, and Selenophene

A series of electroactive triarylamine porous organic polymers (POPs) with furan, thiophene, and selenophene (POP-O, POP-S, and POP-Se) linkers have been synthesised and their electronic and spectroscopic properties investigated as a function of redox state. Solid state NMR provided insight into the structural features of the POPs, while in situ solid state Vis-NIR and electron paramagnetic resonance spectroelectrochemistry showed that the distinct redox states in POP-S could be reversibly accessed. The development of redox-active porous organic polymers with heterocyclic linkers affords their potential application as stimuli responsive materials in gas storage, catalysis, and as electrochromic materials.

Spectroelectrochemical properties of a Ru(ii) complex with a thiazolo[5,4-d]thiazole triarylamine ligand

A new electroactive bridging ligand based on the donor (triarylamine) and acceptor (thiazolothiazole) units has been designed and incorporated into a diruthenium complex.

Redox state manipulation of a tris(p-tetrazolylphenyl)amine ligand and its Mn2+ coordination frameworks

Two new Mn²⁺-based metal–organic frameworks containing the tris(p-tetrazolylphenyl)amine (H₃TTPA) ligand exhibit multiple redox-accessible states which have been interrogated using in situ solid state spectroelectrochemical methods.

In Situ Spectroelectrochemical Investigations of RuII Complexes with Bispyrazolyl Methane Triarylamine Ligands

The synthesis and characterization of two triarylamine ligands, 4-(di(1H-pyrazol-1-yl)methyl)-N-(4-(di(1H-pyrazol-1-yl)methyl)phenyl)-N-phenylaniline (TPA-2bpm) and tris(4-(di(1H-pyrazol-1-yl)methyl)phenyl)amine (TPA-3bpm), containing the bispyrazolylmethane moiety and its RuII terpyridine complexes are presented. The redox properties of the ligands and RuII complexes are explored in detail through cyclic and square-wave voltammetry in addition to in situ UV-vis-near infrared, electron paramagnetic resonance, and fluorescence spectroelectrochemistry. It was demonstrated that the triarylamine radical cation was able to be generated, and further, TPA-2bpm underwent an electrochemically induced dimerization process.

In Situ Spectroelectrochemical Investigations of the Redox-Active Tris[4-(pyridin-4-yl)phenyl]amine Ligand and a Zn(2+) Coordination Framework

An investigation of the redox-active tris[4-(pyridin-4-yl)phenyl]amine (NPy3) ligand in the solution state and upon its incorporation into the solid-state metal-organic framework (MOF) [Zn(NPy3)(NO2)2·xMeOH·xDMF]n (MeOH = methanol and DMF = N,N-dimethylformamide) was conducted using in situ UV/vis/near-IR, electron paramagentic resonance (EPR), and fluorescence spectroelectrochemical experiments. Through this multifaceted approach, the properties of the ligand and framework were elucidated and quantified as a function of the redox state of the triarylamine core, which can undergo a one-electron oxidation to its radical cation. The use of pulsed EPR experiments revealed that the radical generated was highly delocalized throughout the entire ligand backbone. This combination of techniques provides comprehensive insight into electronic delocalization in a framework system and demonstrates the utility of in situ spectroelectrochemical methods in assessing electroactive MOFs.

Income Inequality and Child Mortality in Wealthy Nations

This chapter presents evidence of a relationship between child mortality data and socio-economic factors in relatively wealthy nations. The original study on child mortality that is reported here, which first appeared in a UK medical journal, was undertaken in a school of business by academics with accounting and finance backgrounds. The rationale explaining why academics from such disciplines were drawn to investigate these issues is given in the first part of the chapter. The findings related to child mortality data were identified as a special case of a wide range of social and health indicators that are systematically related to the different organisational approaches of capitalist societies. In particular, the so-called Anglo-American countries show consistently poor outcomes over a number of indicators, including child mortality. Considerable evidence has been adduced in the literature to show the importance of income inequality as an explanation for such findings. An important part of the chapter is the overview of a relatively recent publication in the epidemiological literature entitled The Spirit Level: Why Equality Is Better for Everyone, which was written by Wilkinson and Pickett.

Dinuclear Ruthenium Complex Based on a π-Extended Bridging Ligand with Redox-Active Tetrathiafulvalene and 1,10-Phenanthroline Units

The synthesis of a π-extended bridging ligand with both redox-active tetrathiafulvalene (TTF) and 1,10-phenanthroline (phen) units, namely, bis(1,10-phenanthro[5,6-b])tetrathiafulvalene (BPTTF), was realized via a self-coupling reaction. Using this ligand and Ru(tbbpy)2Cl2 (tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine), the dinuclear ruthenium(II) compound [{Ru(tbbpy)2}2(BPTTF)](PF6)4 (1) has been obtained by microwave-assisted synthesis. Structural characterization of 1 revealed a crossed arrangement of the TTF moieties on adjacent dimers within the crystal structure. The optical and redox properties of 1 were investigated using electrochemical, spectroelectrochemical, electron paramagnetic resonance (EPR), and absorption spectroscopic studies combined with theoretical calculations. One exhibits a rich electrochemical behavior owing to the multiple redox-active centers. Interestingly, both the ligand BPTTF and the ruthenium compound 1 are EPR-active in the solid state owing to intramolecular charge-transfer processes. The results demonstrate that the TTF-annulated bis(phen) ligand is a promising bridging ligand to construct oligomeric or polymeric metal complexes with multiple redox-active centers.

Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn

The spin dynamics of Cr₈Mn, a nine‐membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr₈Mn is a rare example of a large odd‐membered AF ring, and has an odd‐number of 3d‐electrons present. Odd‐membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated‐spin ground states. The chemical synthesis and structures of two Cr₈Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground‐spin‐state crossing from S=1/2 to S=3/2 in Cr₈Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin‐pair correlations and scalar‐spin chirality, shows a non‐collinear spin structure that fluctuates between non‐planar states of opposite chiralities.

A monometallic lanthanide bis(methanediide) single molecule magnet with a large energy barrier and complex spin relaxation behaviour

We report a dysprosium(iii) bis(methanediide) single molecule magnet (SMM) where stabilisation of the highly magnetic states and suppression of mixing of opposite magnetic projections is imposed by a linear arrangement of negatively-charged donor atoms supported by weak neutral donors. Treatment of [Ln(BIPMTMS)(BIPMTMSH)] [Ln = Dy, 1Dy; Y, 1Y; BIPMTMS = {C(PPh2NSiMe3)2}2-; BIPMTMSH = {HC(PPh2NSiMe3)2}-] with benzyl potassium/18-crown-6 ether (18C6) in THF afforded [Ln(BIPMTMS)2][K(18C6)(THF)2] [Ln = Dy, 2Dy; Y, 2Y]. AC magnetic measurements of 2Dy in zero DC field show temperature- and frequency-dependent SMM behaviour. Orbach relaxation dominates at high temperature, but at lower temperatures a second-order Raman process dominates. Complex 2Dy exhibits two thermally activated energy barriers (U eff) of 721 and 813 K, the largest U eff values for any monometallic dysprosium(iii) complex. Dilution experiments confirm the molecular origin of this phenomenon. Complex 2Dy has rich magnetic dynamics; field-cooled (FC)/zero-field cooled (ZFC) susceptibility measurements show a clear divergence at 16 K, meaning the magnetic observables are out-of-equilibrium below this temperature, however the maximum in ZFC, which conventionally defines the blocking temperature, T B, is found at 10 K. Magnetic hysteresis is also observed in 10% 2Dy@2Y at these temperatures. Ab initio calculations suggest the lowest three Kramers doublets of the ground 6H15/2 multiplet of 2Dy are essentially pure, well-isolated |±15/2, |±13/2 and |±11/2 states quantised along the C[double bond, length as m-dash]Dy[double bond, length as m-dash]C axis. Thermal relaxation occurs via the 4th and 5th doublets, verified experimentally for the first time, and calculated U eff values of 742 and 810 K compare very well to experimental magnetism and luminescence data. This work validates a design strategy towards realising high-temperature SMMs and produces unusual spin relaxation behaviour where the magnetic observables are out-of-equilibrium some 6 K above the formal blocking temperature.

Electronic Structure of a Mixed-Metal Fluoride-Centered Triangle Complex: A Potential Qubit Component

A novel fluoride-centered triangular-bridged carboxylate complex, [Ni2Cr(μ3-F)(O2C(t)Bu)6(HO2C(t)Bu)3] (1), is reported. Simple postsynthetic substitution of the terminal pivalic acids in 1 with pyridine and 4-methylpyridine led to the isolation of [Ni2Cr(μ3-F)(O2C(t)Bu)6(C5H5N)3] (2) and [Ni2Cr(μ3-F)(O2C(t)Bu)6((4-CH3)C5H4N)3] (3). Structural and magnetic characterizations carried out on the series reveal a dominating antiferromagnetic interaction between the nickel and chromium centers leading to an S = (1)/2 ground state with a very unusual value of geff = 2.48.