One of the main drawbacks of metal-supported materials, traditionally prepared by the impregnation of metal salts onto pre-synthesized porous supports, is the formation of large and unevenly dispersed particles. Generally, the larger are the particles, the lower is the number of catalytic sites. Maximum atom exposure can be reached within single-atom materials, which appear therefore as the next generation of porous catalysts. ExperimentsHerein, we designed single iron atom-supported silica materials through sol-gel hydrothermal treatment using mixtures of a non-ionic surfactant (Pluronic P123) and a metallosurfactant (cetyltrimethylammoniumtrichloromonobromoferrate, CTAF) as porogens. The ratio between the Pluronic P123 and the CTAF enables to control the silica structural and textural properties. More importantly, CTAF acts as an iron source, which amount could be simply tuned by varying the non-ionic/metallo surfactants molar ratio. FindingsThe fine distribution of iron atoms onto the silica mesopores results from the iron distribution within the mixed micelles, which serve as templates for the polymerization of the silica matrix. Several characterization methods were used to determine the structural and textural properties of the silica material (XRD, N 2 sorption isotherms and TEM) and the homogeneous distribution and lack of clustering of iron atoms in the resulting materials (elemental analysis, magnetic measurements, pair distribution function (PDF), MAS-NMR and TEM mapping).The oxidation and spin state of single-iron atoms determined from their magnetic properties were confirmed by DFT calculations. This strategy might find straightforward applications in preparing versatile single atom catalysts, with improved efficiency compared to nanosized ones.
Charge density studies on a few octahedrally coordinated Fe(II) complexes will be presented. The spin state of Fe(II) exhibits either high spin (HS) or low spin (LS) depending upon the ligand field strength of the coordinated ligands. Electron density distribution around the metal should be greatly different for the two spin states, namely a quintet 5 T 2 and a singlet 1 A 1 states. In order to eliminate any possible experimental differences, we choose a few systems where a HS and a LS state coexist in the same lattice. The comparison of these two spin states are quite clear, it gives a good example for the illustration of the d-orbital distributions of the 3d-transition metal as well as the metal-ligand bond for HS and LS state respectively in Fe(II) complexes. Complimentary x-ray absorption spectroscopy and the IR stretching frequency are also measured to monitor the spin transition. A DFT calculation is studied on one of the isolated molecules, comparable electron density distribution as well as the topological properties associated with the bond critical point with respect to the experimental observations will be discussed. The analysis of chemical bonding in real space can be performed using different position dependent functionals. Recently proposed Electron Localizability Indicator (ELI) is based on integrals over specially designed micro-cells [1]. Loosely speaking, ELI is proportional to the charge that is needed to form a same-spin electron pair. Thus, ELI is connected with the correlation of electronic motion of same-spin electrons [2]. In regions of space, where the bonding occurs, the same-spin electron try to avoid each other. The examination of metal-ligand bonds is complicated by the participation of the inner shell metal orbitals [3]. Some strategies, how to approach this difficult task will be presented. MS10 O2 Metal-ligand bonds in coordination compounds[1] Kohout M., Int. J. Quantum Chem., 2004, 97, 651. [2] Kohout M., Pernal K., Wagner F.R., Grin, Yu., Theor. Chem. Acc. 2004, 112, 453. [3] Kohout M., Wagner F.R., Grin, Yu., Theor. Chem. Acc. 2002, 108, 150. . Experimental deformation densities allow a first qualitative view of the non-spherical density and reveal fine details, coherent with the chemistry of the molecule, as for instance lack of electron density in the C-F bond [4][5][6], and larger density accumulation on imidazole moiety C-N and C-O bonds. The topological analysis of the total electron density performed using the VMoPro program [7] will be discussed. As the electrostatic properties are of major importance in numerous biological processes, accurate electrostatic potential and interaction energies calculations of the human aldose reductase complex with fidarestat will also be discussed. This will enable to give useful insight on the specific inhibition activity. Phys. Chem. B. 108,[3663][3664][3665][3666][3667][3668][3669][3670][3671][3672] [7] Jelsch, C., Guillot, B., Lagoutte, A. & Lecomte, C. (2005 The nature of the metal-metal bond in polynuclear transition me...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.