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- Karim, A., et al.
(author)
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The three-center-four-electron tetrel bond
- 2018
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Conference paper (peer-reviewed)abstract
- We present a thermodynamically stable complex that possesses a three-center-four-electron (3c4e) tetrel bond [1,2], formed by capturing a reactive carbenium ion with a bidentate Lewis base. We report NMR spectroscopic, titration calorimetric and reaction kinetic evidences for the structure of this pentacoordinate species and discuss the properties of its tetrel bond, [N˜˜˜∙∙∙C∙∙∙˜˜˜N]+, in comparison with the analogous halogen, [N˜˜˜∙∙∙X∙∙∙˜˜˜N]+ and hydrogen, [N∙∙∙˜˜˜H∙∙∙˜˜˜N]+, bonds [3]. The necessity of the involvement of a bidentate Lewis base for the formation of a stable 3c4e tetrel bond is demonstrated by providing spectroscopic and crystallographic evidence, that a monodentate Lewis base induces a reaction rather than stabilizing the reactive species. A vastly decreased Lewis basicity of the bidentate ligand or reduced Lewis acidity of the carbenium ion weakens — or even prohibits — the formation of the pentacoordinate species, whereas synthetic modifications facilitating attractive orbital overlaps promote it. As the geometry of the pentacoordinate complex resembles the SN2 transition state, it may provide a model system for the investigation of fundamental reaction mechanisms and chemical bonding theories [4].References1. G.C. Pimentel J. Chem. Phys. 1951, 19, 446-4482. R.H. Crabtree Chem. Soc. Rev. 2017, 46, 1720-1729.3. S.B. Hakkert, M. Erdelyi J. Phys. Org. Chem. 2015, 95, 2572-25784. Karim, N. Schultz, H. Andersson, B. Nekoueishahraki et al, 2018, submitted.
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- Atilaw, Yoseph, et al.
(author)
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Prenylated Flavonoids from the Roots of Tephrosia rhodesica
- 2020
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In: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 83:8, s. 2390-2398
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Journal article (peer-reviewed)abstract
- Five new compounds-rhodimer (1), rhodiflavan A (2), rhodiflavan B (3), rhodiflavan C (4), and rhodacarpin (5)-along with 16 known secondary metabolites, were isolated from the CH2Cl2-CH3OH (1:1) extract of the roots of Tephrosia rhodesica. They were identified by NMR spectroscopic, mass spectrometric, X-ray crystallographic, and ECD spectroscopic analyses. The crude extract and the isolated compounds 2-5, 9, 15, and 21 showed activity (100% at 10 mu g and IC50 = 5-15 mu M) against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.
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- Shkolnikov, Vladimir M., et al.
(author)
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Increasing absolute mortality disparities by education in Finland, Norway and Sweden, 1971-2000
- 2012
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In: Journal of Epidemiology and Community Health. - : BMJ. - 0143-005X .- 1470-2738. ; 66:4, s. 372-378
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Journal article (peer-reviewed)abstract
- Background and objectives Studies on socioeconomic health disparities often suffer from a lack of uniform data and methodology. Using high quality, census-linked data and sensible inequality measures, this study documents the changes in absolute and relative mortality differences by education in Finland, Norway and Sweden over the period 1971 to 2000.Methods The age-standardised mortality rates and the population exposures for three educational categories were computed from detailed data provided by the national statistical offices. Mortality disparities by education were assessed using two range measures (rate differences and rate ratios), and two Gini-like measures (the average inter-group difference (AID) and the Gini coefficient (G)). The formulae for the decomposition of the change in the AID into (1) the contribution of change in population composition by education, and (2) the contribution of mortality change were introduced.Results Mortality decreases were often greater for high than for medium and low education. Both relative and absolute mortality disparities tend to increase over time. The magnitude and timing of the increases in absolute disparities vary by country. Both the rate differences and the AIDs have increased since the 1970s in Norway and Sweden, and since the 1980s in Finland. The contributions of the changes in population composition to the total AID increase were substantial in all countries, and for both sexes. The mortality contributions were substantial for males in Norway and Sweden.Conclusions The study reports increases in absolute mortality disparity, and its components. This trend needs to be further studied and addressed by policies.
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