Density-Functional Theory Study of the Stereochemistry of Chloroiron(III) and Chloromanganese(III) Complexes of a Bridled Chiroporphyrin

Transition metal complexes of chiroporphyrins, in which two adjacent meso substituents are linked by a strap of eight methylene groups, [M(BCP8)], can exist as either an αααα or αβαβ atropisomer depending on the nature of the coordinated metal cation. This remarkable conformational versatility was investigated by density-functional theory calculations for the d5 chloroiron(III) complex in the low-spin and high-spin states and for the d4 high-spin chloromanganese(III) complex. The lowest-lying electronic state of all of the conformers of the chloroiron(III) bridled chiroporphyrin is found to be the high-spin state. For the chloroiron(III) complex in the low-spin or the high-spin state and for the high-spin chloromanganese(III) complex, the most stable form is predicted to be the αααα conformer in which the chloride axial ligand is located within the cavity provided by the bridles. The predicted stereochemistries are compared with those similarly obtained (i) for the chloroiron(III) and chloromanganese(III) complexes of the tetramethylchiroporphyrin, which is devoid of straps, and (ii) for the d10 zinc(II) and low-spin d8 nickel(II) BCP8 complexes, on the basis of the effects tied to the occupancy of the stereochemically active dx2−y2-type antibonding orbital level, to the restraints imposed by the straps, and to the presence of the axial chloride ligand

Chiroptical and Computational Studies of a Bridled Chiroporphyrin and of Its Nickel(II), Copper(II), and Zinc(II) Complexes

Circular dichroism (CD) spectra and density functional theory (DFT) calculations are reported for a series of conformationally bistable chiroporphyrins with 8-methylene bridles MBCP-8, which can display either an αααα or an αβαβ orientation of their meso substituents. From DFT geometry optimizations, the most stable form of ZnBCP-8 is found to be the αααα conformer. By passing to NiBCP-8, there is a strong stabilization of the αβαβ conformation with respect to the αααα conformation, consistent with the X-ray structures of αααα-ZnBCP-8 and αβαβ-NiBCP-8. A correlation between the sign of the CD signal in the Soret region and the conformation of the BCP-8 compounds is reported: the αααα conformers H2BCP-8 and ZnBCP-8 show a positive CD signal, whereas the αβαβ conformers NiBCP-8 and CuBCP-8 exhibit a negative signal. The possible contributions to the rotational strengths of αβαβ-NiBCP-8 and αααα-ZnBCP-8, calculated on the basis of their crystal structures, have been analyzed. The CD signals are found to result from a combination of both the inherent chirality of the porphyrin and of extrinsic contributions due to the chiral bridles. These results may have a broad significance for understanding the chiroptical properties of chiral porphyrins and hemoproteins and for monitoring stimuli-responsive, conformationally bistable chiroporphyrin compounds

Photoswitching of the Dielectric Constant of the Spin-Crossover Complex [Fe(L)(CN)2]H2O

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Barriers and facilitators to development and implementation of a rural primary health care intervention for dementia: a process evaluation

Abstract Background With rural population aging there are growing numbers of people with dementia in rural and remote settings. The role of primary health care (PHC) is critical in rural locations, yet there is a lack of rural-specific PHC models for dementia, and little is known about factors influencing the development, implementation, and sustainability of rural PHC interventions. Using a community-based participatory research approach, researchers collaborated with a rural PHC team to co-design and implement an evidence-based interdisciplinary rural PHC memory clinic in the Canadian province of Saskatchewan. This paper reports barriers and facilitators to developing, implementing, and sustaining the intervention. Methods A qualitative longitudinal process evaluation was conducted over two and half years, from pre- to post-implementation. Data collection and analyses were guided by the Consolidated Framework for Implementation Research (CFIR) which consists of 38 constructs within five domains: innovation characteristics, outer setting, inner setting, individual characteristics, and process. Data were collected via focus groups with the PHC team and stakeholders, smaller team workgroup meetings, and team member interviews. Analysis was conducted using a deductive approach to apply CFIR codes to the data and an inductive analysis to identify barriers and facilitators. Results Across all domains, 14 constructs influenced development and implementation. Three domains (innovation characteristics, inner setting, process) were most important. Facilitators were the relative advantage of the intervention, ability to trial on a small scale, tension for change, leadership engagement, availability of resources, education and support from researchers, increased self-efficacy, and engagement of champions. Barriers included the complexity of multiple intervention components, required practice changes, lack of formal incentive programs, time intensiveness of modifying the EMR during iterative development, lack of EMR access by all team members, lack of co-location of team members, workload and busy clinical schedules, inability to justify a designated dementia care manager role, and turnover of PHC team members. Conclusions The study identified key factors that supported and hindered the development and implementation of a rural-specific strategy for dementia assessment and management in PHC. Despite challenges related to the rural context, the researcher-academic partnership was successful in developing and implementing the intervention

Risques climatiques et agriculture en Afrique de l’Ouest

Le futur de l’Afrique de l’Ouest dépend de la capacité du secteur de l’agriculture à s’adapter pour garantir la sécurité alimentaire dans un contexte de changement climatique et de croissance démographique. Pour faciliter cette adaptation, la recherche a déployé d’importants efforts pour améliorer les connaissances sur les mécanismes climatiques et leurs impacts sur les systèmes agropastoraux. Or, ces avancées issues de la recherche ne sont que rarement prises en compte dans la planification et la prise de décision. Partant de ce constat, un projet de recherche « Agriculture et gestion des risques climatiques : outils et recherches en Afrique », soutenu par le ministère français des Affaires étrangères et du Développement international est mené entre 2016 et 2018 dans plusieurs pays d’Afrique de l’Ouest. Il a pour objectif d’élaborer des outils efficaces de gestion du risque climatique pour les agriculteurs, en co-construisant avec des réseaux de chercheurs et d’acteurs directement impliqués dans l’accompagnement de l’agriculture des stratégies innovantes basées sur les résultats de la recherche. Cet ouvrage restitue les principales avancées de cette recherche-action sur trois thématiques prioritaires : les services climatiques pour l’agriculture, la gestion des ressources en eau et l’intensification écologique. Il permet aux acteurs du secteur agricole (organisations paysannes, filières, secteur privé agricole, banques de développement agricole, fournisseurs d’intrants, services agricoles et de météorologie) de s’approprier de nouvelles connaissances et de nouveaux outils pour une meilleure prise en compte des risques climatiques dans la gestion des systèmes de production