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$_3$ and CsSnBr$_3$ 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