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Creators/Authors contains: "Maiola, Michela L."

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  1. Abstract

    We employ a metal‐metal salt metathesis strategy to access low‐valent tantalum‐copper heterometallic architectures (Ta−μ2‐H2−Cu and Ta−μ3‐H2−Cu3) that emulate structural elements proposed for surface alloyed nanomaterials. Whereas cluster assembly with carbonylmetalates is well precedented, the use of the corresponding polyarene transition metal anions is underexplored, despite recognition of these highly reactive fragments as storable sources of atomic Mn−. Our application of this strategy provides structurally unique early‐late bimetallic species. These complexes incorporate bridging hydride ligands during their syntheses, the origin of which is elucidated via detailed isotopic labelling studies. Modification of ancillary ligand sterics and electronics alters the mechanism of bimetallic assembly; a trinuclear complex resulting from dinuclear C−H activation is demonstrated as an intermediateen routeto formation of the bimetallic. Further validating the promise of this rational, bottom‐up approach, a unique tetranuclear species was synthesized, featuring a Ta centre bearing three Ta−Cu interactions.

     
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  2. Abstract

    We employ a metal‐metal salt metathesis strategy to access low‐valent tantalum‐copper heterometallic architectures (Ta−μ2‐H2−Cu and Ta−μ3‐H2−Cu3) that emulate structural elements proposed for surface alloyed nanomaterials. Whereas cluster assembly with carbonylmetalates is well precedented, the use of the corresponding polyarene transition metal anions is underexplored, despite recognition of these highly reactive fragments as storable sources of atomic Mn−. Our application of this strategy provides structurally unique early‐late bimetallic species. These complexes incorporate bridging hydride ligands during their syntheses, the origin of which is elucidated via detailed isotopic labelling studies. Modification of ancillary ligand sterics and electronics alters the mechanism of bimetallic assembly; a trinuclear complex resulting from dinuclear C−H activation is demonstrated as an intermediateen routeto formation of the bimetallic. Further validating the promise of this rational, bottom‐up approach, a unique tetranuclear species was synthesized, featuring a Ta centre bearing three Ta−Cu interactions.

     
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  3. Abstract

    Lindqvist polyoxovanadate‐alkoxide (POV‐alkoxide) clusters are excellent candidates for applications in energy storage and conversion due to their rich electrochemical profiles. One approach to tune the redox properties of these cluster complexes is through substitutional cationic doping within the hexavanadate core. Here, we report the synthesis of a series of tungsten‐substituted POV‐alkoxide clusters with one and two tungsten atoms. Soft landing of mass‐selected ions was used to purify heterometal POV‐alkoxides that cannot be readily separated using conventional approaches. The soft landed POV‐alkoxides are characterized using infrared reflection‐absorption spectroscopy and electrospray ionization mass spectrometry. The redox properties of the isolated ions are examined using an in situ electrochemical cell which enables traditional in vacuo electrochemical measurements inside of an ion soft landing instrument. Although the overall cluster core retains redox activity after tungsten doping, vanadium‐based redox couples (VV/VIV) are shifted substantially, indicating a pronounced effect of a heteroatom on the electronic structure of the core.

     
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  4. Here, we expand on the synthesis and characterization of chloride-functionalized polyoxovanadate-alkoxide (POV-alkoxide) clusters, to include the halogenation of mixed-valent vanadium oxide assemblies. These findings build on our previously disclosed results describing the preparation of a mono-anionic chloride-functionalized cluster, [V 6 O 6 Cl(OC 2 H 5 ) 12 ] 1− , by chlorination of [V 6 O 7 (OC 2 H 5 ) 12 ] 2− with AlCl 3 , aimed at understanding the electronic consequences of the introduction of halide-defects in bulk metal oxides ( e.g. VO 2 ). While chlorination of the mixed-valent POV-ethoxide clusters was not possible using AlCl 3 , we have found that the chloride-substituted oxidized derivatives of the Lindqvist vanadium-oxide clusters can be formed using TiCl 3 (thf) 3 with [V 6 O 7 (OC 2 H 5 ) 12 ] n ( n = 1−, 0) or WCl 6 with [V 6 O 7 (OC 2 H 5 ) 12 ] 0 . Characterization of the chloride-containing products, [V 6 O 6 Cl(OC 2 H 5 ) 12 ] n ( n = 0, 1+), was accomplished via 1 H NMR spectroscopy, X-ray crystallography, and elemental analysis. Electronic analysis of the redox series of Cl-doped POV-alkoxide clusters via infrared and electronic absorption spectroscopies revealed all redox events are localized to the vanadyl portion of the cluster, with the site differentiated V III –Cl moiety retaining its reduced oxidation state across a 1.9 V window. These results present new synthetic routes for accessing chloride-doped POV-alkoxide clusters from mixed-valent vanadium oxide precursors. 
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