1,323 research outputs found
Hexakis(1H-imidazole-κN 3)manganese(II) triaquatris(1H-imidazole-κN 3)manganese(II) bis(naphthalene-1,4-dicarboxylate)
In the crystal structure of the title compound, [Mn(C3H4N2)6][Mn(C3H4N2)3(H2O)3](C12H6O4)2, there are uncoordinated naphthalenedicarboxylate dianions and two kinds of MnII complex cations, both assuming a distorted octahedral geometry. One MnII cation is located on an inversion center and is coordinated by six imidazole molecules, while the other MnII cation is located on a twofold rotation axis and is coordinated by three water molecules and three imidazole units. The naphthalenedicarboxylate dianions are linked to both MnII complex cations via O—H⋯O and N—H⋯O hydrogen bonding, but no π–π stacking is observed between aromatic rings in the crystal structure
Hexakis(1H-imidazole-κN 3)cobalt(II) triaquatris(1H-imidazole-κN 3)cobalt(II) bis(naphthalene-1,4-dicarboxylate)
The asymmetric unit of the title compound, [Co(C3H4N2)6][Co(C3H4N2)3(H2O)3](C12H6O4)2, contains two halves of crystallographically independent CoII complex cations, each assuming a distorted octahedral geometry, and one uncoordinated naphthalene-1,4-dicarboxylate dianion. One CoII cation is located on an inversion center and is coordinated by six imidazole molecules, while the other CoII cation is located on a twofold rotation axis and is coordinated by three water and three imidazole molecules. The uncoordinated naphthalene-1,4-dicarboxylate dianion links both CoII complex cations via O—H⋯O and N—H⋯O hydrogen bonding. One imidazole ligand is equally disordered over two sites about a twofold rotation axis, while the coordinated N atom of the imidazole is located on the twofold rotation axis. One water O atom has site symmetry 2
Bis(μ-4-chloro-2-oxidobenzoato)bis[(1,10-phenanthroline)copper(II)] dihydrate
The structure of the the title compound, [Cu2(C7H3ClO3)2(C12H8N2)2]·2H2O, consists of a dimeric unit involving a planar Cu2O2 group arranged around an inversion center. The coordination sphere of the CuII atom can be described as an elongated distorted square pyramid where the basal plane is formed by the two N atoms of the 1,10-phenanthroline molecule and the two O atoms of the hydroxychlorobenzoate (hcbe) anion. The long apical Cu—O distance of 2.569 (2) Å involves the O atom of a symmetry-related hcbe anion, building up the dinuclear unit. Each dinuclear unit is connected through O—H⋯O hydrogen bonds involving two water molecules, resulting in an R
4
2(8) graph-set motif and building up an infinite chain parallel to (10). C—H⋯O interactions further stabilize the chain
Converting normal insulators into topological insulators via tuning orbital levels
Tuning the spin-orbit coupling strength via foreign element doping and/or
modifying bonding strength via strain engineering are the major routes to
convert normal insulators to topological insulators. We here propose an
alternative strategy to realize topological phase transition by tuning the
orbital level. Following this strategy, our first-principles calculations
demonstrate that a topological phase transition in some cubic perovskite-type
compounds CsGeBr and CsSnBr could be facilitated by carbon
substitutional doping. Such unique topological phase transition predominantly
results from the lower orbital energy of the carbon dopant, which can pull down
the conduction bands and even induce band inversion. Beyond conventional
approaches, our finding of tuning the orbital level may greatly expand the
range of topologically nontrivial materials
Large-gap quantum spin Hall insulators in tin films
The search of large-gap quantum spin Hall (QSH) insulators and effective
approaches to tune QSH states is important for both fundamental and practical
interests. Based on first-principles calculations we find two-dimensional tin
films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large
for practical applications at room temperature. These QSH states can be
effectively tuned by chemical functionalization and by external strain. The
mechanism for the QSH effect in this system is band inversion at the \Gamma
point, similar to the case of HgTe quantum well. With surface doping of
magnetic elements, the quantum anomalous Hall effect could also be realized
Tetraaquabis(pyridine-3-sulfonato-κN)nickel(II)
In the molecule of the title compound, [Ni(C5H4NO3S)2(H2O)4], the NiII cation is located on an inversion center and is coordinated by four water molecules and two pyridine-3-sulfonate anions with an NiN2O4 distorted octahedral geometry. The face-to-face separation of 3.561 (5) Å between parallel pyridine rings indicates the existence of weak π–π stacking between the pyridine rings. The structure also contains intermolecular O—H⋯O hydrogen bonding and weak C—H⋯O hydrogen bonding
Triaqua(3-carboxy-5-sulfonatobenzoato-κO 1)(1,10-phenanthroline-κ2 N,N′)cobalt(II) monohydrate
In the title compound, [Co(C8H4O7S)(C12H8N2)(H2O)3]·H2O, the CoII cation is coordinated by one sulfoisophthalate dianion, one bidentate phenathroline (phen) molecule and three water molecules in a distorted cis-CoN2O4 octahedral geometry. In the crystal structure, aromatic π–π stacking occurs [centroid–centroid distances 3.7630 (14) and 3.7269 (15) Å], as well as an extensive O—H⋯O and C—H⋯O hydrogen-bonding networ
Tetrakis(μ2-phenylacetato-κ2 O:O′)bis[(isoquinoline-κN)copper(II)]
In the title centrosymmetric binuclear CuII complex, [Cu2(C8H7O2)4(C9H7N)2], the two Cu cations are bridged by four carboxylate groups of the phenylacetate anions; each Cu cation is further coordinated by an isoquinoline ligand to complete the distorted CuO4N square-pyramidal geometry. The Cu cation is displaced by 0.2092 (8) Å from the basal plane formed by the four O atoms. Within the dinuclear molecule, the Cu⋯Cu separation is 2.6453 (6) Å. Although a parallel, overlapped arrangement of isoquinoline ligands exists in the crystal structure; the longer face-to-face distance of 3.667 (5) Å suggests there is no π–π stacking between isoquinoline ring systems
Bis(μ-3-hydroxybenzoato)-κ2 O 1:O 3;κ2 O 3:O 1-bis[bis(1H-benzimidazole-κN 3)(3-hydroxybenzoato-κO)nickel(II)] bis(1H-benzimidazole-κN 3)bis(3-hydroxybenzoato-κO 1)nickel(II) hexahydrate
The title compound, [Ni2(C7H5O3)4(C7H6N2)4][Ni(C7H5O3)2(C7H6N2)2]·6H2O, is a mononuclear/dinuclear nickel(II) cocrystal, the two molecular species interacting through hydrogen bonds that involve the uncoordinated water molecules. In the mononuclear species, the NiII ion, located on an inversion center, is coordinated by two 1H-benzimidazole (bzim) ligands and two 3-hydroxybenzoate (hba) anions in a square-planar geometry. In the centrosymmetric dinuclear species, the NiII ion is coordinated by two bzim ligands and three hba anions in a square-pyramidal geometry; of the two independent hba anions, one bridges two NiII ions with both carboxylate and hydroxyl groups whereas the other coordinates in a unidentate manner to the NiII ion. The apical Ni—Ohydroxyl bond is 0.39 Å longer than the basal Ni—Ocarboxyl bonds. The face-to-face separation of 3.326 (9) Å indicates the existence of π–π stacking between parallel bzim ligands of adjacent dinuclear entities. Extensive N—H⋯O and O—H⋯O hydrogen bonds help to stabilize the crystal structure
[(E)-But-2-enoato-κO]chlorido(2,2′-diamino-4,4′-bi-1,3-thiazole-κ2 N 3,N 3′)zinc(II) monohydrate
In the title compound, [Zn(C4H5O2)Cl(C6H6N4S2)]·H2O, the ZnII cation is coordinated by a bidentate diaminobithiazole (DABT) ligand, a but-2-enoate anion and a Cl− anion in a distorted tetrahedral geometry. Within the DABT ligand, the two thiazole rings are twisted to each other at a dihedral angle of 4.38 (10)°. An intramolecular N—H⋯O interaction occurs. The centroid–centroid distance of 3.6650 (17) Å and partially overlapped arrangement between nearly parallel thiazole rings of adjacent complexes indicate the existence of π–π stacking in the crystal structure. Extensive O—H⋯Cl, O—H⋯O, N—H⋯Cl and N—H⋯O hydrogen bonding helps to stabilize the crystal structure
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