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

To what extent is behaviour a problem in English schools?:Exploring the scale and prevalence of deficits in classroom climate

The working atmosphere in the classroom is an important variable in the process of education in schools, with several studies suggesting that classroom climate is an important influence on pupil attainment. There are wide differences in the extent to which classroom climate is considered to be a problem in English schools. Some ‘official’ reports suggest that behaviour in schools is ‘satisfactory or better’ in the vast majority of schools; other sources have pointed to behaviour being a serious and widespread problem. The paper details four studies conducted over the past decade which aimed to explore these disparities. The aim of the research was to gain a more accurate insight into the extent to which deficits in classroom climate limit educational attainment and equality of educational opportunity in English schools. The findings question the suggestion that behaviour is satisfactory or better in 99.7% of English schools and the concluding section suggests ways in which deficits in classroom climate might be addressed. Although the study is limited to classrooms in England, OECD studies suggest that deficits in the working atmosphere in classrooms occur in many countries. The study therefore has potential relevance for education systems in other countries

Analysis of Multi-Element Airfoil High Lift Improvement by Efficient Upper Surface Suction

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A Multidisciplinary Preoperative Teaching Session for Women Awaiting Breast Cancer Surgery: A Quality Improvement Initiative

Purpose: Most of the breast cancer diagnoses are recommended for breast surgery. Unfortunately, many patients report preoperative anxiety, which can affect postoperative recovery. Preoperative teaching sessions have been shown to reduce anxiety and improve recovery for the patients with breast cancer. To better support the patients at our cancer center, a multidisciplinary preoperative teaching session was developed and delivered as a quality improvement initiative. Methods: Participants scheduled for breast surgery were invited to attend a group-delivered preoperative teaching session, either for breast-conserving surgery or mastectomy. The sessions were presented by a nurse, occupational therapist, and physiotherapist. Data were collected through a researcher-developed 2-item questionnaire administered before and after sessions to compare self-reported anxiety and knowledge levels, along with qualitative feedback. Results: A total of 94 participants attended the preoperative sessions, piloted over a year. The majority were scheduled for breast-conserving surgery. Wilcoxon signed rank tests showed that after session, self-reported levels of anxiety decreased, whereas levels of knowledge increased. Most participants found the session to be very helpful and would recommend it to other patients/families awaiting surgery. Conclusions: Patients awaiting surgery for breast cancer may be better supported through a multidisciplinary group teaching session by decreasing anxiety and improving knowledge related to the procedure. Future directions could explore the effect of specific session elements on anxiety, knowledge, and postoperative complications using psychometrically sound instruments and additional time points. Implications for cancer survivors: Standardization of these preoperative teaching sessions may enhance breast cancer care, reduce postoperative complications, and improve patient recovery