Reversible M?M Bonding by Alkaline Earth Metals (Mg,Ca, Sr,Ba) in Graphite Intercalation Compounds |
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Authors: | Wei Xu Dr Karoly Kozma Tianxiang Sha Yi-Jen Wu Prof May Nyman Prof Michael M Lerner |
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Institution: | Department of Chemistry, Oregon State University, Corvallis, Oregon, 97331-4003 United States |
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Abstract: | The alkaline earth metals (M=Mg, Ca, Sr, and Ba) exhibit a +2 oxidation state in nearly all known stable compounds, but MI dimeric complexes with M?M bonding, M2(en)2]2+, (en=ethylenediamine) of all these metals can be stabilized within the galleries of donor-type graphite intercalation compounds (GICs). These metals can also form GICs with more conventional metal (II) ion complexes, M(en)2]2+. Here, the facile interconversion between dimeric-MI and monomeric-MII intercalates upon the addition/removal of en are reported. Thermogravimetry, powder X-ray diffraction, and pair distribution function analysis of total scattering data support the presence of either M2(en)2]2+ or M(en)2]2+ guests. This phase conversion requires coupling graphene and metal redox centers, with associated reversible M?M bond formation within graphene galleries. This chemistry allows the facile isolation of unusual oxidation states, reveals M0→M2+ reaction pathways, and present new opportunities in the design of hybrid conversion/intercalation materials for applications such as charge storage. |
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Keywords: | alkaline earth metals amines graphite intercalations non-covalent interactions |
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