Garrett E Granroth

Publications (3)4.6 Total impact

• Source

  Available from: missouri.edu

  Article: Dimethylammonium trichlorocuprate(II): structural transition, low-temperature crystal structure, and unusual two-magnetic chain structure dictated by nonbonding chloride-chloride contacts.

  Roger D Willett, Brendan Twamley, Wouter Montfrooij, Garrett E Granroth, Stephen E Nagler, Donavan W Hall, Ju-Hyun Park, Brian C Watson, Mark W Meisel, Daniel R Talham
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  ABSTRACT: Catena(dimethylammonium-bis(mu2-chloro)-chlorocuprate), (CH3)2NH2CuCl3, forms chains of Cu2Cl6(2-) bifold dimers linked along the structural chain axis by terminal chlorides forming long semicoordinate bonds to adjacent dimers. The structural chains are separated by dimethylammonium ions that hydrogen bond to chloride ions of the dimers. A structural phase transition below room temperature removes disorder in the hydrogen bonding, leaving adjacent dimers along the chain structurally and magnetically inequivalent, with alternating ferromagnetic and antiferromagnetic pairs. The coupled dimers are magnetically isolated from each other along the structural chain axis by the long semicoordinate Cu-Cl bond. However, the dimers couple to like counterparts on adjacent chains via nonbonding Cl...Cl contacts. The result is two independent magnetic chains, one an alternating antiferromagnetic chain and the other an antiferromagnetic chain of ferromagnetically coupled copper dimers, which run perpendicular to the structural chains. This magnetostructural analysis is used to fit unusual low-temperature (1.6 K) magnetization vs field data that display a two-step saturation. The structural phase transition is identified with neutron scattering and capacitance measurements, and the X-ray crystal structures are determined at room temperature and 84 K. The results appear to resolve long-standing confusion about the origins of the magnetic behavior of this compound and provide a compelling example of the importance of two-halide magnetic exchange.
  Inorganic Chemistry 10/2006; 45(19):7689-97. · 4.60 Impact Factor
• Source

  Available from: chemistry.uah.edu

  Article: New BEDT-TTF Salts Incorporating the Hydrogen Dichloride (HCl2-) Anion

  Brian H. Ward, Garrett E. Granroth, Khalil A. Abboud, Mark W. Meisel, Daniel R. Talham
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  ABSTRACT: Salts of the π-donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) have been isolated with hydrogen dichloride (HCl2-) as the counterion. Two phases were obtained, α‘-BEDT-TTF2(HCl2) (1) and ε-BEDT-TTF(HCl2) (2), by electrocrystallization from solvent mixtures containing ClCH2COCl. Like previously described α‘-BEDT-TTF2X salts, 1 contains sheets of twisted BEDT-TTF dimers, and conductivity and magnetic susceptibility are consistent with a description of nearly localized (BEDT-TTF)2+ radicals. Salt 2, space group C2/m, undergoes an anion ordering structural phase transition near 200 K, resulting in a new low-temperature phase ε‘-BEDT-TTF(HCl2) (3) with space group P21/c. Below 170 K, 3 undergoes a magnetic phase transition seen in electron paramagnetic resonance data. The HCl2- ion is linear in 1 but bent in 2 and 3. α‘-(BEDT-TTF)2(HCl2), 1, crystallizes in the P2/c space group with a = 7.7023(1) Å, b = 6.6140(1) Å, c = 30.1077(6) Å, β = 96.506(1)°, V = 1523.90(4) Å3, and Z = 2. ε-BEDT-TTF(HCl2), 2, crystallizes in the C2/m space group with a = 12.9687(8) Å, b = 11.6077(8) Å, c = 5.6949(4) Å, β = 104.688(1)°, V = 829.28(10) Å3, and Z = 2. ε‘-BEDT-TTF(HCl2), 3, belongs to the P21/cspace group with a = 12.7112(1) Å, b = 11.5778(2) Å, c = 11.3583(1) Å, β = 101.194(1)°, V = 1639.77(3) Å3, and Z = 4.
  03/1998;
• Article: Langmuir−Blodgett Films of Known Layered Solids:  Preparation and Structural Properties of Octadecylphosphonate Bilayers with Divalent Metals and Characterization of a Magnetic Langmuir−Blodgett Film

  Candace T. Seip, Garrett E. Granroth, Mark W. Meisel, Daniel R. Talham
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  ABSTRACT: Langmuir−Blodgett (LB) films of a series of divalent metal octadecylphosphonates have been prepared and characterized. The films are each shown to be LB analogs of known solid-state metal phosphonates possessing 2-dimensional ionic−covalent metal phosphonate layers. The metal phosphonate layers crystallize during the LB deposition process. Films were characterized with XPS, X-ray diffraction, ellipsometry, attenuated total reflectance FTIR, and, in the case of the manganese film, SQUID magnetometry. Octadecylphosphonate films with Mn2+, Mg2+, and Cd2+ form with the stoichiometry M(O3PC17H37)·H2O and have metal phosphonate bonding consistent with the analogous M(O3PR)·H2O layered solids. The Ca2+ film forms as Ca(HO3PC18H37)2, which is also a known solid-state phase. Magnetic measurements reveal that the manganese octadecylphosphonate film undergoes a magnetic ordering transition at 13.5 K resulting in a “weak ferromagnet”. The behavior is similar to that of the known layered solid-state manganese alkylphosphonates which are also “weak ferromagnets”. The magnetic ordering is antiferromagnetic where incomplete cancellation of the magnetic sublattices, due to low site symmetry, results in a spontaneous magnetization. A spin-flop transition is observed at 2.5 T in magnetization vs applied field measurements of the ordered state. The film also exhibits magnetic memory, with a small remnant magnetization and a coercive field of 20 mT at 2 K. The results demonstrate that magnetic ordering phenomena can be incorporated into LB films and that LB film methods can be used to prepare monolayer and multilayer films of known solid-state materials.
  07/1997;