What Controls the Magnetic Exchange and Anisotropy in a Family of Tetranuclear {Mn2IIMn2III} Single-Molecule Magnets?

© 2017 American Chemical Society.Twelve heterovalent, tetranuclear manganese(II/III) planar diamond or “butterfly” complexes, 1-12, have been synthesized and structurally characterized, and their magnetic properties have been probed using experimental and theoretical techniques. The 12 structures are divided into two distinct “classes”. Compounds 1-8 place the Mn(III), S = 2, ions in the body positions of the butterfly metallic core, while the Mn(II), S = 5/2, ions occupy the outer wing sites and are described as “Class 1”. Compounds 9-12 display the reverse arrangement of ions and are described as “Class 2”. Direct current susceptibility measurements for 1-12 reveal ground spin states ranging from S = 1 to S = 9, with each complex displaying unique magnetic exchange parameters (J). Alternating current susceptibility measurements found that that slow magnetic relaxation is observed for all complexes, except for 10 and 12, and display differing anisotropy barriers to magnetization reversal. First, we determined the magnitude of the magnetic exchange parameters for all complexes. Three exchange coupling constants (Jbb, Jwb, and Jww) were determined by DFT methods which are found to be in good agreement with the experimental fits. It was found that the orientation of the Jahn-Teller axes and the Mn-Mn distances play a pivotal role in determining the sign and strength of the Jbb parameter. Extensive magneto-structural correlations have been developed for the two classes of {MnII2MnIII2} butterfly complexes by varying the Mnb-O distance, Mnw-O distance, Mnb-O-Mnb angle (α), Mnb-O-Mnb-O dihedral angle (γ), and out-of-plane shift of the Mnw atoms (β). For the magnetic anisotropy the DFT calculations yielded larger negative D value for complexes 2, 3, 4, and 6 compared to the other complexes. This is found to be correlated to the electron-donating/withdrawing substituents attached to the ligand moiety and suggests a possible way to fine tune the magnetic anisotropy in polynuclear Mn ion complexes

New examples of triangular terbium(iii) and holmium(iii) and hexagonal dysprosium(iii) single molecule toroics

© 2019 The Royal Society of Chemistry. The structural, magnetic and theoretical aspects are described for three triangular lanthanide complexes, [TbIII3(OH)(teaH2)3(paa)3]Cl2 (1), [DyIII3(OH)(teaH2)3(paa)3]Cl2 (2) and [HoIII3(OH)(teaH2)3(paa)3]Cl2 (3), and a hexanuclear wheel of formula [DyIII6(pdeaH)6(NO3)6] (4) [teaH3 = triethanolamine, paaH = N-(2-pyridyl)-acetoacetamide and pdeaH3 = 3-[bis(2-hydroxyethyl)amino]propan-1-ol]. Each complex displays single molecule toroidal behaviour as rationalised using high-level ab initio calculations. Complexes 2 and 3 are the first examples of mixed moment single molecule toroidal complexes featuring non-Kramers ions

Rationalizing the sign and magnitude of the magnetic coupling and anisotropy in dinuclear manganese(iii) complexes

© 2018 The Royal Society of Chemistry. We have synthesised twelve manganese(iii) dinuclear complexes, 1-12, in order to understand the origin of magnetic exchange (J) between the metal centres and the magnetic anisotropy (D) of each metal ion using a combined experimental and theoretical approach. All twelve complexes contain the same bridging ligand environment of one μ-oxo and two μ-carboxylato, that helped us to probe how the structural parameters, such as bond distance, bond angle and especially Jahn-Teller dihedral angle affect the magnetic behaviour. Among the twelve complexes, we found ferromagnetic coupling for five and antiferromagnetic coupling for seven. DFT computed the J and ab initio methods computed the D parameter, and are in general agreement with the experimentally determined values. The dihedral angle between the two Jahn-Teller axes of the constituent MnIII ions are found to play a key role in determining the sign of the magnetic coupling. Magneto-structural correlations are developed by varying the Mn-O distance and the Mn-O-Mn angle to understand how the magnetic coupling changes upon these structural changes. Among the developed correlations, the Mn-O distance is found to be the most sensitive parameter that switches the sign of the magnetic coupling from negative to positive. The single-ion zero-field splitting of the MnIII centres is found to be negative for complexes 1-11 and positive for complex 12. However, the zero-field splitting of the S = 4 state for the ferromagnetic coupled dimers is found to be positive, revealing a significant contribution from the exchange anisotropy-a parameter which has long been ignored as being too small to be effective

Improving the oral health of older people in care homes (TOPIC): a protocol for a feasibility study

BACKGROUND: Evidence for interventions promoting oral health amongst care home residents is weak. The National Institute for Health and Care Excellence (NICE) guideline NG48 aims to maintain and improve the oral health of care home residents. A co-design process that worked with residents and care home staff to understand how the NG48 guideline could be best implemented in practice has been undertaken to refine a complex intervention. The aim of this study is to assess the feasibility of the intervention to inform a future larger scale definitive trial. METHODS: This is a protocol for a pragmatic cluster randomised controlled trial with a 12-month follow-up that will be undertaken in 12 care homes across two sites (six in London, six in Northern Ireland). Care homes randomised to the intervention arm (n = 6) will receive the complex intervention based on the NG48 guideline, whilst care homes randomised to the control arm (n = 6) will continue with routine practice. The intervention will include a training package for care home staff to promote knowledge and skills in oral health promotion, the use of the Oral Health Assessment Tool on residents by trained care home staff, and a 'support worker assisted' daily tooth-brushing regime with toothpaste containing 1500 ppm fluoride. An average of ten residents, aged 65 years or over who have at least one natural tooth, will be recruited in each care home resulting in a recruited sample of 120 participants. Assessments will be undertaken at baseline, 6 months and 12 months, and will include a dental examination and questionnaires on general health and oral health administered by a research assistant. A parallel process evaluation involving semi-structured interviews will be undertaken to explore how the intervention could be embedded in standard practice. Rates of recruitment and retention, and intervention fidelity will also be recorded. A cost-consequence model will determine the relevance of different outcome measures in the decision-making context. DISCUSSION: The study will provide valuable information for trialists, policymakers, clinicians and care home staff on the feasibility and associated costs of oral health promotion in UK care homes. TRIAL REGISTRATION: ISRCTN10276613. Registered on 17th April 2020. http://www.isrctn.com/ISRCTN10276613

Financial considerations in the conduct of multi-centre randomised controlled trials: evidence from a qualitative study.

National Coordinating Centre for Research Methodology; Medical Research Council, UK Department of Health; Chief Scientist OfficeNot peer reviewedPublisher PD

On misunderstanding Heraclitus: The justice of organisation structure

Writers on organisational change often refer to the cosmology of Heraclitus in their work. Some use these references to support arguments for the constancy and universality of organisational change and the consignment to history of organisational continuity and stability. These writers misunderstand the scope of what Heraclitus said. Other writers focus exclusively on the idea that originated with Heraclitus that the universe is composed of processes and not of things. This idea, which has been particularly associated with Heraclitus’s thought from the time of Plato, does indeed provide a rich source of insights into organisational analysis, not least the current trends towards giving proper attention to processual studies of organisational change. Yet there is some uncertainty as to whether Heraclitus actually said that the universe was composed exclusively of processes rather than things, and even if that was what he thought, he intended his ideas on flux to be understood not in isolation but in the context of other aspects of his cosmology. Writers on organisational change seldom make reference to this wider context. Heraclitus was a rational but also a religious thinker. A central element in his thought was the notion of divine Justice, which to a Greek of his era meant the order of the universe. Remote as his Olympian theology may seem today, it sets a crucial and entirely rational context for understanding his ideas about flux. It means that ideas about continuity and stability were quite as important in Heraclitus’s cosmology as his more commonly quoted ideas about change. This paper sets out an overview of Heraclitus’s philosophy, insofar as it appears to have potential relevance to organisational analysis, and discusses how far it supports or contradicts the ideas that organisational change scholars have drawn from it

Bursaries, writing grants and fellowships: a strategy to develop research capacity in primary health care

BACKGROUND: General practitioners and other primary health care professionals are often the first point of contact for patients requiring health care. Identifying, understanding and linking current evidence to best practice can be challenging and requires at least a basic understanding of research principles and methodologies. However, not all primary health care professionals are trained in research or have research experience. With the aim of enhancing research skills and developing a research culture in primary health care, University Departments of General Practice and Rural Health have been supported since 2000 by the Australian Government funded 'Primary Health Care Research Evaluation and Development (PHCRED) Strategy'. A small grant funding scheme to support primary health care practitioners was implemented through the PHCRED program at Flinders University in South Australia between 2002 and 2005. The scheme incorporated academic mentors and three types of funding support: bursaries, writing grants and research fellowships. This article describes outcomes of the funding scheme and contributes to the debate surrounding the effectiveness of funding schemes as a means of building research capacity. METHODS: Funding recipients who had completed their research were invited to participate in a semi-structured 40-minute telephone interview. Feedback was sought on acquisition of research skills, publication outcomes, development of research capacity, confidence and interest in research, and perception of research. Data were also collected on demographics, research topics, and time needed to complete planned activities. RESULTS: The funding scheme supported 24 bursaries, 11 writing grants, and three research fellows. Nearly half (47%) of all grant recipients were allied health professionals, followed by general practitioners (21%). The majority (70%) were novice and early career researchers. Eighty-nine percent of the grant recipients were interviewed. Capacity, confidence, and level of research skills in ten core areas were generally considered to have improved as a result of the award. More than half (53%) had presented their research and 32% had published or submitted an article in a peer-reviewed journal. CONCLUSION: A small grant and mentoring scheme through a University Department can effectively enhance research skills, confidence, output, and interest in research of primary health care practitioners