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Triosmium Clusters on a Support: Determination of Structure by X‐ray Absorption Spectroscopy and High‐Resolution Microscopy
Author(s) -
Mehraeen Shareghe,
Kulkarni Apoorva,
Chi Miaofang,
Reed Bryan W.,
Okamoto Norihiko L.,
Browning Nigel D.,
Gates Bruce C.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000860
Subject(s) - extended x ray absorption fine structure , scanning transmission electron microscopy , cluster (spacecraft) , spectroscopy , absorption (acoustics) , chemistry , radius , resolution (logic) , crystallography , absorption spectroscopy , analytical chemistry (journal) , surface extended x ray absorption fine structure , materials science , transmission electron microscopy , optics , physics , nanotechnology , computer security , chromatography , quantum mechanics , artificial intelligence , computer science , composite material , programming language
The structures of small, robust metal clusters on a solid support were determined by a combination of spectroscopic and microscopic methods: extended X‐ray absorption fine structure (EXAFS) spectroscopy, scanning transmission electron microscopy (STEM), and aberration‐corrected STEM. The samples were synthesized from [Os 3 (CO) 12 ] on MgO powder to provide supported clusters intended to be triosmium. The results demonstrate that the supported clusters are robust in the absence of oxidants. Conventional high‐angle annular dark‐field (HAADF) STEM images demonstrate a high degree of uniformity of the clusters, with root‐mean‐square (rms) radii of 2.03±0.06 Å. The EXAFS OsOs coordination number of 2.1±0.4 confirms the presence of triosmium clusters on average and correspondingly determines an average rms cluster radius of 2.02±0.04 Å. The high‐resolution STEM images show the individual Os atoms in the clusters, confirming the triangular structures of their frames and determining OsOs distances of 2.80±0.14 Å, matching the EXAFS value of 2.89±0.06 Å. IR and EXAFS spectra demonstrate the presence of CO ligands on the clusters. This set of techniques is recommended as optimal for detailed and reliable structural characterization of supported clusters.