More Like this

1. Calix[4]arene‐Based Bis(Nitric Oxide) Complexes: Synthesis, Physical Properties, and Structural Characterization

   https://doi.org/10.1002/asia.201801683  

   Wang, Denan ; Zhang, Depeng ; Lindeman, Sergey V. ; Rathore, Rajendra ( January 2019 , Chemistry – An Asian Journal)

   Calix[4]arene‐based molecules hold great promise as candidate sensors and storage materials for nitric oxide (NO), owing to their unprecedented binding affinity for NO. However, the structure of calix[4]arene is complicated by the availability of four possible conformers: 1,3‐alternate, 1,2‐alternate, cone, and partial cone (paco). Whilst complexes of NO with several of these conformers have previously been established, the 1,2‐alternate conformer complex, that is, [1,2‐alter⋅NO]⁺, has not been previously reported. Herein, we determine the crystal structure of the NO complex with the 1,2‐alternate conformer for the first time. In addition, we have also found that the 1,2‐alternate and 1,3‐alternate conformers can combine with two NO molecules to form stable bis(nitric oxide) complexes. These new complexes, which exhibit remarkable binding capacity for the construction of NO‐storage molecules, were characterized by using X‐ray crystallography and NMR, IR, and UV/Vis spectroscopy. These findings will extend our understanding of the interactions between nitric oxide and cofacially and non‐cofacially arrayed aromatic rings, and we expect them to aid in the design and development of new supramolecular sensors and storage materials for NO with high capacity and efficacy.

    

   more » « less
2. 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
3. Systemic consequences of disorder in magnetically self-organized topological MnBi 2 Te 4 /(Bi 2 Te 3 ) n superlattices

   https://doi.org/10.1088/2053-1583/ac3cc6  

   Sitnicka, Joanna ; Park, Kyungwha ; Skupiński, Paweł ; Grasza, Krzysztof ; Reszka, Anna ; Sobczak, Kamil ; Borysiuk, Jolanta ; Adamus, Zbigniew ; Tokarczyk, Mateusz ; Avdonin, Andrei ; et al ( December 2021 , 2D Materials)

   Abstract MnBi 2 Te 4 /(Bi 2 Te 3 ) n materials system has recently generated strong interest as a natural platform for the realization of the quantum anomalous Hall (QAH) state. The system is magnetically much better ordered than substitutionally doped materials, however, the detrimental effects of certain disorders are becoming increasingly acknowledged. Here, from compiling structural, compositional, and magnetic metrics of disorder in ferromagnetic (FM) MnBi 2 Te 4 /(Bi 2 Te 3 ) n it is found that migration of Mn between MnBi 2 Te 4 septuple layers (SLs) and otherwise non-magnetic Bi 2 Te 3 quintuple layers (QLs) has systemic consequences—it induces FM coupling of Mn-depleted SLs with Mn-doped QLs, seen in ferromagnetic resonance as an acoustic and optical resonance mode of the two coupled spin subsystems. Even for a large SL separation ( n ≳ 4 QLs) the structure cannot be considered as a stack of uncoupled two-dimensional layers. Angle-resolved photoemission spectroscopy and density functional theory studies show that Mn disorder within an SL causes delocalization of electron wave functions and a change of the surface band structure as compared to the ideal MnBi 2 Te 4 /(Bi 2 Te 3 ) n . These findings highlight the critical importance of inter- and intra-SL disorder towards achieving new QAH platforms as well as exploring novel axion physics in intrinsic topological magnets. 

   more » « less
4. Redox Ladder of Ni 3 Complexes with Closed‐Shell, Mono‐, and Diradical Triphenylene Units: Molecular Models for Conductive 2D MOFs

   https://doi.org/10.1002/anie.202109304  

   Yang, Luming ; Dincă, Mircea ( September 2021 , Angewandte Chemie International Edition)

   We report the isolation and characterization of a series of trinickel complexes with 2,3,6,7,10,11‐hexaoxytriphenylene (HOTP), [(Me₃TPANi)₃(HOTP)](BF₄)_n(Me₃TPA=N,N,N‐tris[(6‐methyl‐2‐pyridyl)methyl]amine) (n=2, 3, 4 for complexes1,2,3). These complexes comprise a redox ladder whereby the HOTP core displays increasingly quinoidal character as its formal oxidation state changes from −4, to −3, and −2 in1,2, and3, respectively. No formal oxidation state changes occur on Ni, allowing the isolation of singlet diradical, monoradical, and closed‐shell configurations for HOTP in1,2, and3, respectively, with a concomitant decrease in the spin coupling strength upon oxidation. Because the three complexes can be considered models of the smallest building blocks of 2D conductive metal‐organic frameworks such as Ni₉HOTP₄, these results serve as possible inspiration for the construction of extended materials with targeted electric and magnetic properties.

    

   more » « less
5. Redox Ladder of Ni 3 Complexes with Closed‐Shell, Mono‐, and Diradical Triphenylene Units: Molecular Models for Conductive 2D MOFs

   https://doi.org/10.1002/ange.202109304  

   Yang, Luming ; Dincă, Mircea ( September 2021 , Angewandte Chemie)

   We report the isolation and characterization of a series of trinickel complexes with 2,3,6,7,10,11‐hexaoxytriphenylene (HOTP), [(Me₃TPANi)₃(HOTP)](BF₄)_n(Me₃TPA=N,N,N‐tris[(6‐methyl‐2‐pyridyl)methyl]amine) (n=2, 3, 4 for complexes1,2,3). These complexes comprise a redox ladder whereby the HOTP core displays increasingly quinoidal character as its formal oxidation state changes from −4, to −3, and −2 in1,2, and3, respectively. No formal oxidation state changes occur on Ni, allowing the isolation of singlet diradical, monoradical, and closed‐shell configurations for HOTP in1,2, and3, respectively, with a concomitant decrease in the spin coupling strength upon oxidation. Because the three complexes can be considered models of the smallest building blocks of 2D conductive metal‐organic frameworks such as Ni₉HOTP₄, these results serve as possible inspiration for the construction of extended materials with targeted electric and magnetic properties.

    

   more » « less