Threefold Rotation Axis Research Articles

Tris(tetrabutylammonium) hexakis(tert-butanethiolato-κS)hepta-μ3-chlorido-μ3-sulfido-hexamolybdate dihydrate

The octa­hedral cluster core of the anion in the structure of the title compound, (C16H36N)3[Mo6(C4H9S)6(μ3-Cl)7(μ3-S)]·2H2O, has -3 site symmetry. Two μ3-Cl atoms fully occupy positions in the cluster core, while the remaining six positions are statistically occupied by Cl and S atoms in a 1:5 ratio. The fully occupied Cl-atom positions are located on sites with 3 symmetry, and the N atom of tetra­butyl­ammonium cation is located on a site with 2 symmetry. The structure contains also two disordered solvent water mol­ecules, one of which is located on a threefold rotation axis and the other in a general position, both with an occupancy of 0.25. The water mol­ecules are localized in cavities formed by the tetra­butyl­ammonium cations and the tert-butane­thiol­ate groups. The metal clusters are stacked in a cubic close packing arrangement along [001].

Giant Improper Ferroelectricity in the Ferroaxial MagnetCaMn7O12

In rhombohedral CaMn7O12, an improper ferroelectric polarization of magnitude 2870 μC m(-2) is induced by an incommensurate helical magnetic structure that evolves below T(N1)=90 K. The electric polarization was found to be constrained to the high symmetry threefold rotation axis of the crystal structure, perpendicular to the in-plane rotation of the magnetic moments. The multiferroicity is explained by the ferroaxial coupling mechanism, which in CaMn7O12 gives rise to the largest magnetically induced, electric polarization measured to date.

Tris(2,2′-bipyridine-κ2N,N′)cobalt(III) tris(oxalato-κ2O1,O2)ferrate(III) monohydrate

The title compound, [Co(C10H8N2)3][Fe(C2O4)3]·H2O, con­sists of two discrete tris­(chelate) metal ions (CoIIIN6 and FeIIIO6 chromophores) and a water mol­ecule. The structure is highly symmetrical; the CoIII and FeIII ions occupy positions with site symmetry 3.2. The coordination polyhedra of the metal atoms have a nearly octa­hedral geometry with noticeable trigonal distortions. The Co—N and Fe—O bond lengths are equal by symmetry, viz. 1.981 (2) and 1.998 (4) Å, respectively. The cations and anions are arranged alternately along their threefold rotation axes parallel to [001], forming chains that are packed in a hexa­gonal manner. The water mol­ecules occupy voids between the chains. The crystal under investigation was an inversion twin.

Critical role of weak [C–H⋯O] hydrogen bonds in the assembly of benzo[1,2-d:4,5-d′]bisoxazole cruciforms into supramolecular sheets

This paper explores the structural patterns adopted by a class of eight conjugated cruciforms based on a benzo[1,2-d:4,5-d′]bisoxazole (BBO) nucleus. Within the series, the lengths of cruciforms' x- and y-axes, as well as their terminal substituents, were varied. Two new cruciforms have been prepared using microwave-assisted Sonogashira couplings. Examination of molecular structures of BBO cruciforms revealed the expected cross-shaped geometries, with ∼90° crossing angles between the two conjugation circuits. Most significant deviations from the idealized planar structures were caused by the distortion of benzene rings positioned along the cruciforms' y-axis from the plane of the central benzobisoxazole ring, by as much as 82.1°. Deviations from linearity within carbon–carbon triple bonds were mild, but additively resulted in notably bent y-axes of the two largest examined cruciforms. Most significantly, the packing patterns of benzobisoxazole cruciforms revealed three distinct organizational motifs. Cruciforms with carbonyl groups on either the horizontal or the vertical axis (or both) all organized into two-dimensional infinite sheets, apparently connected chiefly through [C–H⋯O] contacts that varied in length between 2.24 and 2.60 A, and could be interpreted as weak hydrogen bonds. The parallel layers of these two-dimensional sheets then assembled into three-dimensional structures through [π⋯π] stacking between the layers. The packing patterns of the two cruciforms with 4-(N,N-dimethylamino)phenyl groups on the vertical axis are dominated by one-dimensional columnar or tape-like assemblies that are formed through [π⋯π] stacking; these then organize into two-dimensional sheets, which in turn layer into a three-dimensional structure, but with a ∼60° angle between the adjacent sheets. Finally, in the parent tetraphenyl-substituted cruciform, the sp2 nitrogen on the BBO core plays the key role in the assembly. It establishes 2.64 A-long [C–H⋯N] contacts with the phenyl groups, mediating the formation of a unique packing pattern in which six tilted columnar assemblies of [π⋯π] stacked cruciforms surround a three-fold rotation axis in the crystal.

Tris(tetrahydrofuran-κO)tris[tris(thiophen-2-yl)methanolato-κO]terbium(III) tetrahydrofuran monosolvate

In the mononuclear title compound, [Tb(C13H9OS3)3(C4H8O)3]·C4H8O, the lanthanide cation is located on a threefold rotation axis and is surrounded by electron-rich ligands in an approximately octa­hedral geometry. One of the thienyl groups and the bound THF are disordered with 0.5:0.5 occupancy. The free THF is disordered around the threefold axis.

Fac-Tris(pyridine-2-carboxylato-κ2N,O)cobalt(III)

In the title compound, [Co(C6H4NO2)3], the CoIII ion lies on a threefold rotation axis and is in a distorted octa­hedral environment defined by three N and three O donor atoms from three fac-disposed pyridine-2-carboxyl­ate ligands. The ligands are coordinated in a chelate fashion, forming three five-membered rings. In the crystal, translationally related complex molecules are organized into columns along [001] via C—H⋯O hydrogen bonds.

A new langbeinite-type phosphate: K2AlSn(PO4)3

Single crystals of the title compound, dipotassium aluminium tin(IV) tris­[phosphate(V)], K2AlSn(PO4)3, were synthesized by a high temperature reaction in a platinum crucible. In the structure, the AlIII and SnIV atoms occupy the same site on a threefold rotation axis with occupational disorder in a 1:1 ratio. In the three-dimensional structure, Al/SnO6 octa­hedra and PO4 tetra­hedra are inter­connected via their vertices, yielding a [Al/SnP3O12]n framework. The K atoms (site symmetry 3) reside in the large cavities delimited by the [Al/SnP3O12]n framework, and are surrounded by 12 O atoms.

Tris(6-carboxypyridine-2-carboxylato)terbium(III) 2.75-hydrate

In the title compound, [Tb(C7H4NO4)3]·2.75H2O, the Tb3+ atom is coordinated by three tridentate 6-carb­oxy­pyridine-2-carboxyl­ate ligands and lies on a crystallographic threefold rotation axis. The coordination polyhedron around TbIII adopts a distorted tricapped trigonal–prismatic geometry. Disordered water mol­ecules with partial occupancy are also present in the crystal, one of which is associated with each of the carboxyl­ate O atoms of the complex unit.

Selection Rules for Light-Induced Magnetization of a Crystal with Threefold Symmetry: The Case of Antiferromagnetic NiO

We propose Raman-induced collinear difference-frequency generation (DFG) as a method to manipulate dynamical magnetization. When a fundamental beam propagates along a threefold rotational axis, this coherent second-order optical process is permitted by angular momentum conservation through the rotational analogue of the umklapp process. As a demonstration, we experimentally obtained polarization properties of collinear magnetic DFG along a [111] axis of a single crystal of antiferromagnetic NiO with micromultidomain structure, which excellently agreed with the theoretical prediction.

Hexaaqua-zinc(II) bis-[tris-(3-carb-oxy-pyridine-2-carboxyl-ato)zincate(II)

The title compound, [Zn(H2O)6][Zn(C7H4NO4)3]2, consists of two [Zn(py-2,3-dcH)3]− anions (py-2,3-dcH is 3-carboxy­pyridine-2-carboxylate) and one [Zn(H2O)6]2+ cation. The anion is a six-coordinate complex located on a threefold rotation axis with a slightly distorted octa­hedral geometry around Zn2+ ion. The cation is also six-coordinate with an octa­hedral geometry around the Zn atom, located at a axis. Non-covalent inter­actions such as π–π stacking [centroid–centroid distance = 3.828 (4)Å] and O—H⋯O hydrogen bonds play important roles in stabilizing the supra­molecular structure.

V1.42In1.83Mo15Se19

The structure of the title compound, vanadium indium penta­deca­molybdenum nona­deca­selenide, V1.42In1.83Mo15Se19, is isotypic with In2.9Mo15Se19 [Grüttner et al. (1979 ▶). Acta Cryst. B35, 285–292]. It is characterized by two cluster units Mo6Sei 8Sea 6 and Mo9Sei 11Sea 6 (where i represents inner and a apical atoms) that are present in a 1:1 ratio. The cluster units are centered at Wyckoff positions 2b and 2c and have point-group symmetry and , respectively. The clusters are inter­connected through additional Mo—Se bonds. In the title compound, the V3+ cations replace the trivalent indium atoms present in In2.9Mo15Se19, and a deficiency is observed on the monovalent indium site. One Mo, one Se and the V atom are situated on mirror planes, and two other Se atoms and the In atom are situated on threefold rotation axes.

Electronic and magnetic structure of a triacetylphlorogucinol-bridged [formula omitted]-symmetric trinuclear copper complex: Magnetic characterization, ESR spectroscopy, and DFT calculations

For the trinuclear copper complex [Cu 3(tapg)(H 2bhea) 3](ClO 4) 3 based on the tritopic bridging ligand 2,4,6-triacetylphlorogucinol (H 3tapg) and the capping ligand 2-[bis-(2-hydroxyethyl)amino]ethylamine (H 2bhea) a detailed study on the magnetic and electronic properties is presented. The C 3 -symmetric structure of the molecular assembly is preserved in the solid state structure of the compound which crystallizes in the space group R 3 c with a threefold rotation axis passing through the center of the molecule. Susceptibility measurements show weak ferromagnetic interactions with a coupling constant J = 1.10 ( 4 ) cm - 1 mediated by a spin-polarization mechanism. This is confirmed by DFT calculations according the broken symmetry approach at B3LYP/def2-TZVP level of theory. Extended characterization by ESR spectroscopy both in X- and W-band confirm an exchange-coupled system with axial symmetry with g ⊥ = 2.0633 ( 4 ) , g ‖ = 2.2303 ( 4 ) and an effective axial hyperfine constant A ‖ , eff = 64 G .

2,4,6‐Triacetylphlorogucinol as Threefold Symmetric Bridging Ligand: Synthesis, Structure and Magnetic Properties of the Copper Complex

AbstractIt is shown that 2,4,6‐triacetylphlorogucinol (H3tapg) can be utilized as C3‐symmetric tritopic bridging ligand, that can be regarded as an annulated threefold acetylacetonate. Together with 2‐[bis(2‐hydroxyethyl)amino]ethylamine (H2bhea) as capping ligand the corresponding trinuclear copper complex [Cu3(tapg)(H2bhea)3](ClO4)3 has been synthesized as the first example. The compound crystallizes in the trigonal space group R3c with the complex cation located on a threefold rotation axis. Magnetic measurements reveal a ferromagnetic coupling between the copper centers, which are transmitted through the bridging tapg3– ligand by a spin‐polarization mechanism.

The trigonal polymorph of strontium tetraborate, β-SrB4O7

The asymmetric unit of the title compound, β-SrB4O7, contains five Sr atoms (three located on a threefold rotation axis), twelve B and 21 O atoms. The structure is made up from BO3 triangles and BO4 tetra­hedra in a 1:1 ratio. Pairs of BO3 triangles are linked to BO4 tetra­hedra via common corners, forming chains. These chains are further linked to adjacent chains through corner-sharing, leading to a three-dimensional framework with channels running parallel to [001]. The Sr2+ ions reside in the channels and exhibit strongly distorted polyhedra The density of the β-polymorph is considerably lower than that of α-SrB4O7, which is constructed solely from BO4 tetra­hedra.

Triaqua(1,4,7-triazacyclononane-κ3N1,N4,N7)nickel(II) bromide nitrate

In the title half-sandwich compound, [Ni(C6H15N3)(H2O)3]Br(NO3), the central NiII ion, lying on a threefold rotation axis, is six-coordinated by three amine N atoms from the face-capping triaza macrocycle and three water O atoms in a slightly distorted octa­hedral geometry. In the crystal, O—H⋯O hydrogen bonding and weak O—H⋯Br inter­actions associate the NiII cations and the counter-ions into a three-dimensional supra­molecular network.

Poly[[tris(μ3-2-oxidopyridinium-3-carboxylato)manganese(II)sodium(I)] monohydrate

In the crystal structure of the title compound, {[MnNa(C6H4NO3)3]·H2O}n, the MnII cation is located on a threefold rotation axis and is chelated by three 2-oxidopyridinium-3-carboxyl­ate (opc) anions in an octa­hedal coordination. The NaI cation is located on a threefold rotation axis and is surrounded by six O atoms from three opc anions. The opc anions link the Mn and Na cations, forming a three-dimensional polymeric structure. The uncoordinated water mol­ecule, located on a threefold rotation axis, is equally disordered over two sites. The three-dimensional network is consolidated by N—H⋯O hydrogen bonds.

Tris(propionitrile-κN)[1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane-κ3N1,N4,N7]copper(II) bis(perchlorate) dihydrate

In the title compound, [Cu(C3H5N)3(C12H18N6)](ClO4)2·2H2O, the CuII atom lies on a threefold rotation axis and is coordinated in a distorted N6 octa­hedral environment by three tertiary amines from the tridentate chelating aza­macrocyclic ligand and three propionitrile mol­ecules. Inter­molecular non-classical C—H⋯N hydrogen bonding inter­links the [Cu(C3H5N)3(C12H18N6)]2+ cations into a two-dimensional supra­molecular sheet extending along the ab plane. The crystal packing also exhibits weak C—H⋯O inter­actions.

Tris{aquabis[3-(2-pyridyl)-1H-pyrazole]copper(II)} di-μ9-arsenato-hexatriaconta-μ2-oxido-octadecaoxidooctadecamolybdate(VI)

The title compound, [Cu(C8H7N3)2(H2O)]3[As2Mo18O62], consists of two subunits, viz. an α-Dawson-type [As2Mo18O62]6− anion and a complex [Cu(C8H7N3)2(H2O)]2+ cation. The copper(II) ion (site symmetry .2) is penta­coordinated in a distorted square-pyramidal manner by four N atoms from two chelating 3-(2-pyrid­yl)pyrazole ligands in equatorial positions and one water mol­ecule in the apical position. In the heteropolyanion, two O atoms of the AsO4 group (3. symmetry) are equally disordered about the threefold rotation axis. N—H⋯O and O—H⋯O hydrogen bonding between the neutral mol­ecules and the water mol­ecules leads to a consolidation of the structure.

Hierarchical self-assembly of heteronuclear co-ordination networks

Two ligands L(1) and L(2) have been prepared which contain a chelating pyrazolyl-pyridine group with a pendant aromatic nitrile (in L(1), a benzonitrile; in L(2), a naphthonitrile). These ligands react with Ag(I) salts to give a range of infinite coordination networks or dimeric 'boxes' in which the pyrazolyl-pyridine chelates and the aromatic nitrile groups both participate in coordination to Ag(I) ions. In contrast, L(1) and L(2) form simple mononuclear tris-chelates [ML(3)](2+) with first-row transition metal dications (M = Co, Ni, Zn) in which the aromatic nitrile groups are pendant such that the complexes can be used as 'complex ligands'. The crystal structures of [M(L(2))(3)](BF(4))(2) are based on solely the mer tris-chelate geometry although in solution (1)H NMR spectroscopy reveals a mixture of both fac and mer isomers of the tris-chelates. Reaction of these with Ag(I) ions allows the interaction of the pendant nitrile groups with Ag(i) ions to generate coordination networks based on [ML(3)](2+) cations being crosslinked by Ag(I) ions. In these networks the [ML(3)](2+) cations have solely the fac geometry and lie on threefold rotation axes with all three pendant nitrile groups coordinated to Ag(I) ions which are three-coordinate. {[AgM(L(2))(3)][BF(4)](3)}(infinity) (M = Co, Ni) consist of two interpenetrated (10,3)a nets which have opposite chirality at the [M(L(2))(3)](2+) centres but are not strictly enantiomorphic as the two nets are not crystallographically equivalent. {[AgNi(L(1))(3)](BF(4))(3)}(infinity) in contrast contains two-dimensional sheets which have a (6,3) net structure of hexagonal rings of alternative Ni(II) and Ag(I) centres; although not interpenetrating, two such adjacent (and enantiomorphic) sheets interact with each other via numerous CH...pi interactions between aromatic ligands. Formation of these structures shows that the differential reactivity of the two binding sites in L(1) and L(2) (pyrazolyl-pyridine, and nitrile) can be used to generate mixed-metal coordination networks in a hierarchical, stepwise manner.

CdZn2KB2O6F, a new fluoride borate crystal

During an attempt to grow crystals of the nonlinear optical material Cd(3)Zn(3)B(4)O(12) using a KBF(4) flux, crystals of a new cadmium dizinc potassium borate fluoride compound, CdZn(2)KB(2)O(6)F, were unexpectedly isolated. The structure consists of layers constructed of distorted corner-sharing ZnO(3)F tetrahedra and BO(3) triangles. Both Zn and B reside on threefold rotation axes, while the F(-) anion is located at a site of 3.2 symmetry. The Cd(II) (site symmetry 3) and K(+) (site symmetry 3.2) ions occupy six- and nine-coordinate interlayer sites, respectively. The BO(3) triangles and ZnO(3) pyramids from the ZnO(3)F tetrahedra share bridging O atoms with each other to form an extended [ZnBO(3)] layer parallel to (001). Although these layers are similar to the [MBO(3)] layers seen in other compounds, they are uniquely bridged here by the Cd centres and F(-) anions to form a three-dimensional framework. In so doing, a series of channels is formed along the [010] direction and the K(+) cations are found in these channels.