More Like this

1. Single crystal neutron and magnetic measurements of Rb ₂ Mn ₃ (VO ₄ ) ₂ CO ₃ and K ₂ Co ₃ (VO ₄ ) ₂ CO ₃ with mixed honeycomb and triangular magnetic lattices

   https://doi.org/10.1039/C9DT03389K  

   Smith Pellizzeri, Tiffany M.; Sanjeewa, Liurukara D.; Pellizzeri, Steven; McMillen, Colin D.; Garlea, V. Ovidiu; Ye, Feng; Sefat, Athena S.; Kolis, Joseph W. (April 2020, Dalton Transactions)

   null (Ed.)

   Two new alkali vanadate carbonates with divalent transition metals have been synthesized as large single crystals via a high-temperature (600 °C) hydrothermal technique. Compound I , Rb 2 Mn 3 (VO 4 ) 2 CO 3 , crystallizes in the trigonal crystal system in the space group P 3̄1 c , and compound II , K 2 Co 3 (VO 4 ) 2 CO 3 , crystallizes in the hexagonal space group P 6 3 / m . Both structures contain honeycomb layers and triangular lattices made from edge-sharing MO 6 octahedra and MO 5 trigonal bipyramids, respectively. The honeycomb and triangular layers are connected along the c -axis through tetrahedral [VO 4 ] groups. The MO 5 units are connected with each other by carbonate groups in the ab -plane by forming a triangular magnetic lattice. The difference in space groups between I and II was also investigated with Density Functional Theory (DFT) calculations. Single crystal magnetic characterization of I indicates three magnetic transitions at 77 K, 2.3 K, and 1.5 K. The corresponding magnetic structures for each magnetic transition of I were determined using single crystal neutron diffraction. At 77 K the compound orders in the MnO 6 -honeycomb layer in a Néel-type antiferromagnetic orientation while the MnO 5 triangular lattice ordered below 2.3 K in a colinear ‘up–up–down’ fashion, followed by a planar ‘Y’ type magnetic structure. K 2 Co 3 (VO 4 ) 2 CO 3 ( II ) exhibits a canted antiferromagnetic ordering below T N = 8 K. The Curie–Weiss fit (200–350 K) gives a Curie–Weiss temperature of −42 K suggesting a dominant antiferromagnetic coupling in the Co 2+ magnetic sublattices. 

   more » « less
2. Crystal structure of [[Mo3Se7(S2CNEt2)3]2(μ-Se)] ⋅ 2(C6H4Cl2), C42H68Cl4Mo6N6S12Se15

   https://doi.org/10.1515/ncrs-2019-0938  

   Brakefield, Kyra; Barnes, Justin; Donahue, James P. (April 2020, Zeitschrift für Kristallographie - New Crystal Structures)

   null (Ed.)

   Abstract C 42 H 68 Cl 4 Mo 6 N 6 S 12 Se 15 , triclinic, P 1̄ (no. 2), a = 13.0196(19) Å, b = 18.813(3) Å, c = 19.745(3) Å, α = 117.446(2)°, β = 99.775(2)°, γ = 98.233(2)°, V = 4091.7(10) Å 3 , Z = 2, R gt ( F ) = 0.0557, wR ref ( F 2 ) = 0.1618, T = 150 K. 

   more » « less
3. Correlating magnetic anisotropy with [Mo(CN) ₇ ] ⁴⁻ geometry of Mn ^II –Mo ^III magnetic frameworks

   https://doi.org/10.1039/c9dt02164g  

   Magott, Michał; Dunbar, Kim R.; Pinkowicz, Dawid (January 2019, Dalton Transactions)

   Four new three-dimensional (3-D) coordination frameworks based on the heptacyanomolybdate( iii ) anion were prepared and characterised by magnetic measurements: {[Mn II (imH) 2 ] 2 [Mn II (H 2 O)(imH) 3 ][Mn II (imH) 4 ] [Mo III (CN) 7 ] 2 ·6H 2 O} n ( 1 ) (imH = imidazole), {[Mn II (H 2 O) 2 (imH)] 3 [Mn II (H 2 O)(imH) 2 ][Mo III (CN) 7 ] 2 ·5H 2 O} n ( 2 ), {[Mn II (Htrz)(H 2 O) 2 ][Mn II (Htrz) 0.7 (H 2 O) 2.3 ][Mo III (CN) 7 ]·5.6H 2 O} n ( 3 ) (Htrz = 1,2,4-triazole) and {[Mn II (H 2 O) 2 ] 3 [Mn II (H 2 O) 4 ][Mo III (CN) 7 ] 2 ·6H 2 O·2urea} n ( 4 ). All four compounds exhibit long-range ferrimagnetic ordering and exhibit an opening of their magnetic hysteresis loops at 1.8 K; 1 and 2 exhibit the highest coercive fields among all known [Mo III (CN) 7 ]-based assemblies, 5000 and 4500 Oe respectively. The coercivity of 1–4 is correlated with the geometry of the heptacyanomolybdate( iii ) anion and the cyanide bridging pattern. A paramagnetic analogue of compound 1 , {[Mn II (imH) 2 ] 2 [Mn II (H 2 O)(imH) 3 ][Mn II (imH) 4 ][Re III (CN) 7 ] 2 ·6H 2 O} n ( 1Re ), where the heptacyanomolybdate( iii ) anion is substituted by the diamagnetic heptacyanorhenate( iii ) anion is also reported which constitutes the first example of a coordination framework based on [Re III (CN) 7 ] 4− . 

   more » « less
4. Experimental and theoretical evidence of attractive interactions between dianions: [PdCl ₄ ] ²⁻ ⋯[PdCl ₄ ] ²⁻

   https://doi.org/10.1039/D1CC05640A  

   Zierkiewicz, Wiktor; Michalczyk, Mariusz; Maris, Thierry; Wysokiński, Rafał; Scheiner, Steve (December 2021, Chemical Communications)

   Inspection of the arrangement of tetrachloridopalladate( ii ) centers in a crystalline solid places the Cl of one [PdCl 4 ] 2− directly above the Pd center of its neighbor. A survey of the CSD provides 22 more examples of such MX 4 2− ⋯MX 4 2− complexes, with M being a Group 10 metal and X = Cl, Br, or I. Quantum calculations attribute this arrangement to a π-hole bond wherein Cl lone pairs of one unit transfer charge to vacant orbitals above the Pd center of its neighbor. The stabilizing effect of this bond must overcome the strong Coulombic repulsion between the two dianions, which is facilitated by a polarizable environment as would be present in a crystal, but much more so when the effects of the neighboring counterions are factored in. These conclusions are extended to other [MX 4 ] 2− homodimers, where M represents other members of Group 10, namely Ni and Pt. 

   more » « less
5. Highly active and stable nickel–molybdenum nitride (Ni ₂ Mo ₃ N) electrocatalyst for hydrogen evolution

   https://doi.org/10.1039/D0TA10090K  

   Park, Sang Heon; Jo, Tae Hwan; Lee, Min Hee; Kawashima, Kenta; Mullins, C. Buddie; Lim, Hyung-Kyu; Youn, Duck Hyun (March 2021, Journal of Materials Chemistry A)

   null (Ed.)

   This paper reports a highly active and stable nonprecious metal electrocatalyst based on bimetallic nanoscale nickel molybdenum nitride developed for the hydrogen evolution reaction (HER). A composite of 7 nm Ni 2 Mo 3 N nanoparticles grown on nickel foam (Ni 2 Mo 3 N/NF) was prepared through a simple and economical synthetic method involving one-step annealing of Ni foam, MoCl 5 , and urea without a Ni precursor. The Ni 2 Mo 3 N/NF exhibits high activity with low overpotential ( η 10 of 21.3 mV and η 100 of 123.8 mV) and excellent stability for the HER, achieving one of the best performances among state-of-the-art transition metal nitride based catalysts in alkaline media. Supporting density functional theory (DFT) calculations indicate that N sites in Ni 2 Mo 3 N with a N–Mo coordination number of four have a hydrogen adsorption energy close to that of Pt and hence may be responsible for the enhanced HER performance. 

   more » « less