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  1. 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. 
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    Free, publicly-accessible full text available January 31, 2025
  2. 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. 
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    Free, publicly-accessible full text available July 31, 2024
  3. 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. 
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    Free, publicly-accessible full text available August 28, 2024
  4. 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. 
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    Free, publicly-accessible full text available July 12, 2024
  5. ABSTRACT

    The co-evolution of galaxies and supermassive black holes (SMBHs) underpins our understanding of galaxy evolution, but different methods to measure SMBH masses have only infrequently been cross-checked. We attempt to identify targets to cross-check two of the most accurate methods, megamaser, and cold molecular gas dynamics. Three promising galaxies are selected from all those with existing megamaser SMBH mass measurements. We present Atacama Large Millimeter/sub-millimeter Array (ALMA) 12CO (2–1) and 230-GHz continuum observations with angular resolutions of ≈0${_{.}^{\prime\prime}}$5. Every galaxy has an extended rotating molecular gas disc and 230-GHz continuum source(s), but all also have irregularities and/or non-axisymmetric features: NGC 1194 is highly inclined and has disturbed and lopsided central 12CO (2–1) emission; NGC 3393 has a nuclear disc with fairly regular but patchy 12CO (2–1) emission with little gas near the kinematic major axis, faint emission in the very centre, and two brighter structures reminiscent of a nuclear ring and/or spiral; NGC 5765B has a strong bar and very bright 12CO (2–1) emission concentrated along two bisymmetric offset dust lanes and two bisymmetric nuclear spiral arms. 12CO (2–1) and 12CO (3–2) observations with the James Clerk Maxwell Telescope are compared with the ALMA observations. Because of the disturbed gas kinematics and the impractically long integration times required for higher angular resolution observations, none of the three galaxies is suitable for a future SMBH mass measurement. None the less, increasing the number of molecular gas observations of megamaser galaxies is valuable, and the ubiquitous disturbances suggest a link between large-scale gas properties and the existence of megamasers.

     
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  6. 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.

     
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    Free, publicly-accessible full text available June 20, 2024