skip to main content

Attention:

The NSF Public Access Repository (PAR) system and access will be unavailable from 11:00 PM ET on Thursday, February 13 until 2:00 AM ET on Friday, February 14 due to maintenance. We apologize for the inconvenience.


Search for: All records

Creators/Authors contains: "Smith, Mark D."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Free, publicly-accessible full text available November 19, 2025
  2. Free, publicly-accessible full text available July 18, 2025
  3. Free, publicly-accessible full text available July 27, 2025
  4. The synthesis and structural characterization of the first sulfur-containing derivatives of C,C-biscarborane {ortho-C2B10}2 cluster – thiol, thioether, and disulfide- is reported. The biscarboranyl dithiol (1-HS-C2B10H10)2 exhibits the exceedingly long intracluster carbon-carbon bond length of 1.858(3) Å, which is attributed to the extensive interaction between lone pairs of thiol groups and the unoccupied molecular orbital of carborane cluster. The structures of doubly deprotonated biscarboranyl dithiolate anion (1-S-C2B10H10)22– with various countercations feature even longer carbon-carbon bond of 2.062(10) Å within the cluster along with the short carbon-sulfur bond of 1.660(7) Å, both indicative of significant delocalization of electron density from sulfur atoms into the cluster. 
    more » « less
  5. Mild hydrothermal synthesis was employed to grow high-quality single crystals of ternary fluoridohafnates at low temperatures. The series of new materials was characterized using single crystal X-ray diffraction, and the crystal structures for AHfF6 (A= Mg and Sr), A2HfF8 (A= Ba and Pb), Ca5Hf3F22 and Cd2HfF8(H2O)6 are discussed herein. Although some material compositions have similar stoichiometries, all the compositions adopt different structural motifs. A comparison of the crystal structures and synthesis techniques of ternary fluoridohafnates and ternary fluoridozirconates is also reported, and the impact of the subtle changes of synthesis conditions on overall structures is discussed. 
    more » « less
  6. Geometric magnetic frustration arises when the geometry of a structure prevents the simultaneous fulfillment of nearest-neighbor antiferromagnetic interactions and is commonly observed in lattices that exhibit a triangular topology, such as those found in the pyrochlore structure. Via a mild hydrothermal route, we have synthesized seven quaternary β-pyrochlore related fluorides AxM2+xM3+(2–x)F6, (A = Cs and Rb; M2+ = Co2+, Ni2+ and Zn2+; and M3+ = V3+ and Fe3+). Crystal structures and compositions were determined using a combination of single-crystal X-ray diffraction and energy-dispersive spectroscopy. After adjusting the reaction conditions, phase pure products of AxM2+xM3+(2–x)F6 were obtained. The magnetic susceptibility and isothermal magnetization data for all seven compounds were collected to interpret the magnetic behavior, which ranged from paramagnetic to antiferromagnetic with and without a ferromagnetic component. We found that the magnetic behavior of the AxM2+xV3+(2–x)F6 pyrochlore structures strongly depends on the presence or absence of unpaired electrons on the M2+ position. The titled pyrochlore compounds, with the exception of the Zn-analog, can be considered frustrated materials, with frustration indices in the range of 6 –13. 
    more » « less
  7. We report the synthesis and characterization of a nickel(II) complex of the dicarboranyl CNC dianionic pincer ligand, which activates acetonitrile by C–C bond cleavage. Deprotonation of the relatively acidic C–H bond of the coordinated acetonitrile with potassium t-butoxide led to the formation of the C-bound cyanomethylene ligand at the metal center. Unlike most previously characterized Ni(II) cyanoalkyls, the resulting complex exhibited quick transformation under aerobic conditions at room temperature to afford CNC-ligated nickel(II) cyanide, indicating facile cleavage of the C–CN bond. The cyanoalkyl and cyanide complexes were isolated in excellent yields and characterized by NMR spectroscopy and single-crystal X-ray diffraction. Carbon-containing products of the aerobic C–CN bond activation are hydroxyacetonitrile, formaldehyde, cyanomethyl formate, and carbon dioxide. 
    more » « less
  8. Single crystals of A3MF6(A = Rb, Cs; M = Al, Ga) were grown from mixed alkali chloride/fluoride fluxes. The polymorphism of each compound was studiedviaTGA/DSC and high temperature X-ray diffraction.

     
    more » « less