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11.
Marie-Louise Wind Santina Hoof Dr. Christian Herwig Dr. Beatrice Braun-Cula Prof. Christian Limberg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(22):5743-5750
In recent years, it has become clear that the presence of redox-inactive Lewis acidic metal ions can decisively influence the reactivity of metal–dioxygen moieties that are formed in the course of O2 activation, in molecular complexes, and metalloenzymes. Superoxide species are often formed as the primary intermediates but they are mostly too unstable for a thorough investigation. We report here a series of chromium(III) superoxide complexes [L2Cr]M2O2(THF)y (L=−OSiPh2OSiPh2O−, M+=Li+, Na+, K+ and y=4, 5), which could be accessed, studied spectroscopically and partly crystallized at low temperatures. They only differ in the two incorporated Lewis acidic alkali metal counterions (M+) and it could thus be shown that the nature of M+ determines considerably its interaction with the superoxide ligand. This interaction, in turn, has a significant influence on the stability and reactivity of these complexes towards substrates with OH groups. Furthermore, we show that stability and reactivity are also highly solvent dependent (THF versus nitriles), as donor solvents coordinate to the alkali metal ions and thus also influence their interaction with the superoxide moiety. Altogether, these results provide a comprehensive and detailed picture concerning the correlation between spectroscopic properties, structure, and behavior of such superoxides, that may be exemplary for other systems. 相似文献
12.
Tomy Abhishek Razzanelli Matteo Di Lauro Francesco Rus Daniela Della Santina Cosimo 《Nonlinear dynamics》2022,109(1):249-263
When an epidemic spreads into a population, it is often impractical or impossible to continuously monitor all subjects involved. As an alternative, we propose using algorithmic solutions that can infer the state of the whole population from a limited number of measures. We analyze the capability of deep neural networks to solve this challenging task. We base our proposed architecture on Graph Convolutional Neural Networks. As such, it can reason on the effect of the underlying social network structure, which is recognized as the main component in spreading an epidemic. The proposed architecture can reconstruct the entire state with accuracy above 70%, as proven by two scenarios modeled on the CoVid-19 pandemic. The first is a generic homogeneous population, and the second is a toy model of the Boston metropolitan area. Note that no retraining of the architecture is necessary when changing the model.
相似文献13.
Matthias Keck Santina Hoof Varun Rawat Arkadi Vigalok Christian Limberg 《无机化学与普通化学杂志》2020,646(13):904-908
A calix[4]arene, in which two of the phenol functions are replaced by pyrazole units, [H2(bpzCal)], was investigated as a ligand for Cu+, Ag+ and Au+ ions. Using [Cu(MeCN)4]BF4 and AgSbF6 as the precursors, complexes [MH2(bpzCal)]X (M = Cu, X = BF4; M = Ag, X = SbF6) were formed, where the calixarene ligands adopt a 1,3-alternate structure and the metal ions are coordinated linearly by the two pyrazolyl donors. [CuH2(bpzCal)]BF4 displayed a – for copper(I) complexes – unusual stability towards O2, which is due to the steric protection of the CuI center. By contrast a dinuclear copper(I) complex [Cu2(bpzCal)] that was obtained through treatment of [H2(bpzCal)] with two equivalents of Cu(HMDS) is rather sensitive towards O2. The preparation of a gold complex required the employment of a gold precursor, which contains one labile and one stabilizing neutral ligand, namely [(PPh3)Au(NCMe)]SbF6, which led to the formation of [(PPh3)AuH2(bpzCal)]SbF6. In this complex [H2(bpzCal)] acts only as a monodentate ligand for the gold center. Taken together, the results demonstrate the potential of [H2(bpzCal)] in providing rather different coordination spheres for metal ions. 相似文献
14.
Aiming at structural and functional mimics of the active site of the NiII containing quercetin‐2,4‐dioxygenase NiII flavonolate complexes Tp*NiX [Tp* = hydrotris(3,5‐dimethyl)pyrazolylborate, X = 3‐hydroxy flavonolate (Fla), 3‐hydroxy thioflavonolate (SFla), 3‐hydroxy selenoflavonolate (SeFla)] were synthesized and characterized by spectroscopic methods and X‐ray crystallography. The complex Tp*NiFla reacts with O2 via dioxygenation of bound flavonolate to benzoic acid and salicylic acid as one should expect for a functional model of the enzyme. Modification of the carbonyl function of the flavonolate to the corresponding C=S and C=Se compounds retained dioxygenase like reactivity, but did not lead to an increase of reaction rate as had been anticipated due to a weaker interaction of S/Se with the central nickel atom. 相似文献