Double Zigzag Chains Research Articles

A cyanide-bridged FeII/FeIII mixed-valence chain exhibiting spin transition in the Fe(II) sites

A cyanide-bridged {FeIII2FeII}n one-dimensional chain {[Fe(Tp)(CN)3]2Fe(btb)}n (1) (Tp = hydrotris(pyrazolyl)borate, btb = 1,4-(1H-1,2,4-triazole)butane) has been synthesized via the hydrothermal reaction of Li[Fe(Tp)(CN)3], btb, and FeII(ClO4)2·6H2O at 120 °C. Single-crystal X-ray analysis reveals that compound 1 is an isolated neutral mixed-valence {FeIII2FeII}n double-zigzag chain with each [FeIII(Tp)(CN)3]− unit connecting with two Fe(II) centres via two of its three CN− groups in the cis-positions, and two triazole groups from btb coordinated with Fe(II) ion in its axial positions. Single-crystal data obtained at different temperature together with magnetic data indicate that complex 1 exhibits thermal induced spin transition in the Fe(II) sites with T1/2 ≈ 165 K. Additionally, light-induced excited spin-state trapping (LIESST) of 1 was also observed at low temperature.

Building Nitridic Networks with Phosphorus and Germanium-from GeIIP2N4 to GeIVPN3.

Nitridophosphates and nitridogermanates attract high interest in current research due to their structural versatility. Herein, the elastic properties of GeP2N4 were investigated by single-crystal X-ray diffraction (XRD) upon compression to 44.4(1) GPa in a diamond anvil cell. Its isothermal bulk modulus was determined to be 82(6) GPa. At 44.4(1) GPa, laser heating resulted in the formation of multiple crystalline phases, one of which was identified as unprecedented germanium nitridophosphate GePN3. Its structure was elucidated from single-crystal XRD data (C2/c (no. 15), a = 8.666(5), b = 8.076(4), c = 4.691(2) Å, β = 101.00(7)°) and is built up from layers of GeN6 octahedra and PN4 tetrahedra. The GeN6 octahedra form double zigzag chains, while the PN4 tetrahedra are found in single zigzag chains. GePN3 can be recovered to ambient conditions with a unit cell volume increase of about 12%. It combines PV and GeIV in a condensed nitridic network for the first time.

Unusual photoinduced crystal structure dynamics in TaTe2 with double zigzag chain superstructure

Transition metal dichalcogenides with superperiodic lattice distortions have been widely investigated as the platform of ultrafast structural phase manipulations. Here we performed ultrafast electron diffraction on RT TaTe2, which exhibits a peculiar double zigzag chain pattern of Ta atoms. From the time-dependent electron diffraction pattern, we revealed a photoinduced change in the crystal structure occurring within <0.5 ps, although there is no corresponding high-temperature equilibrium phase. We further clarified the slower response (∼1.5 ps) reflecting the lattice thermalization. Our result suggests the unusual ultrafast crystal structure dynamics specific to the non-equilibrium transient process in TaTe2.

Observation of local atomic displacements intrinsic to the double zigzag chain structure of 1T−MTe2 ( M=V, Nb, Ta )

We describe the existence of local distortion discovered in the synchrotron x-ray single-crystal structure analysis of layered ditelluride $1T\text{\ensuremath{-}}M{\mathrm{Te}}_{2} (M=\mathrm{V}$, Nb, Ta). In $1T\text{\ensuremath{-}}{\mathrm{TaTe}}_{2}$, the double zigzag chain structure of Ta is deformed at about 170 K, and heptamer molecules are formed periodically at low temperatures. We found that some of the Ta atoms that compose the double zigzag chain structure appearing at high temperatures are locally displaced, resulting in local dimerization. This tendency weakens when Ta is replaced by V or Nb. Our results indicate that the local distortion persistently survives in these ditellurides, where the electronic degrees of freedom, including orbitals, are weakened. We further discuss the origin of local distortion in these ditellurides, which is different from many usual material systems where molecular formation occurs at low temperatures.

Fine structure of the charge density wave in bulk VTe2

Vanadium ditelluride (VTe2) has been intensively explored to understand the charge density wave (CDW) phase and its connection to magnetic properties. Here, we conduct a systematic study to understand the fine structure of CDW via scanning tunneling microscopy (STM) combined with density functional theory (DFT) calculations. STM topograph at 79 K shows that a CDW phase in VTe2 has a stripe modulation with 3 × 1 periodicity, following the double zigzag chain of distorted Te lattices. Interestingly, the 3 × 1 CDW modulation undergoes contrast inversion between filled and empty state topographs. Atomistic features and contrast changes of CDW observed in STM are clearly reproduced in our DFT simulation images. Charge distribution calculation indicates that the spatial extension and density of Te 5p orbitals have strong variations with filled and empty states, explaining the fine structure of 3 × 1 CDW in VTe2. Our finding provides an inspiring insight to further research on the less explored electronic structure of VTe2.

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe 2 Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe ₂ Co} Coordination Polymers via Metal-to-Metal Charge Transfer

High Aluminum Ordering in SSZ-59: Residual 1H–27Al Dipolar Coupling Effects in 1H MAS NMR Spectra of Brønsted Acid Sites in Zeolites

The extra-large pore zeolite SSZ-59 was prepared with highly ordered Al atoms in T6 positions within the double-zigzag chains (dzc) running along the 14 MR channels. Narrow 1H MAS NMR signals of br...

Structures of disodium hydrogen citrate mono-hydrate, Na2HC6H5O7(H2O), and di-ammonium sodium citrate, (NH4)2NaC6H5O7, from powder diffraction data.

The crystal structures of disodium hydrogen citrate monohydrate, Na2HC6H5O7(H2O), and di-ammonium sodium citrate, (NH4)2NaC6H5O7, have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. In NaHC6H5O7(H2O), the NaO6 coordination polyhedra share edges, forming zigzag layers lying parallel to the bc plane. The hydro-phobic methyl-ene groups occupy the inter-layer spaces. The carb-oxy-lic acid group makes a strong charge-assisted hydrogen bond to the central carboxyl-ate group. The hydroxyl group makes an intra-molecular hydrogen bond to an ionized terminal carboxyl-ate oxygen atom. Each hydrogen atom of the water mol-ecule acts as a donor, to a terminal carboxyl-ate and the hydroxyl group. Both the Na substructure and the hydrogen bonding differ from those of the known phase Na2HC6H5O7(H2O)1.5. In (NH4)2NaC6H5O7, the NaO6 coordination octa-hedra share corners, making double zigzag chains propagating along the b-axis direction. Each hydrogen atom of the ammonium ions acts as a donor in a discrete N-H⋯O hydrogen bond. The hydroxyl group forms an intra-molecular O-H⋯O hydrogen bond to a terminal carboxyl-ate oxygen atom.

Exotic bonding interactions and coexistence of chemically distinct periodic lattice distortions in the charge density wave compound TaTe2

The superstructure of $\mathrm{TaT}{\mathrm{e}}_{2}$ is examined by total high-energy x-ray scattering and large-scale structure modeling over a broad temperature range. At room temperature, it features double zigzag chains of Ta atoms exhibiting metallic bonding. The chains are sandwiched between planes of weakly interacting Te atoms. Below 170 K, the chains appear broken to ``butterflylike'' clusters and single zigzag chains of covalently bonded Te atoms emerge while Ta-Te interactions remain largely ionic. This is a rare example of a charge density wave compound stabilized by bonding that is a mix of covalent, ionic, and metallic character giving rise to chemically distinct periodic lattice distortions. We argue that the formation of periodic lattice distortions in the Te sublattice in addition to those in the Ta sublattice favors charge delocalization, which may explain the unusually diminished resistivity and increased magnetic susceptibility exhibited by the low-temperature charge density wave phase of $\mathrm{TaT}{\mathrm{e}}_{2}$. The effect may be common for $5d$ transition metal chalcogenides containing Te because of the extended electronic orbitals of the constituent atoms.

Synthesis, Structures, and Properties of Five Metal‐Organic Frameworks Based on Oxidized 3,3′‐Azodibenzoic Acid and Different N‐Donor Ligands

Self‐assembly of transition metal ions with different N‐donor ligands and 3,3′‐azodibenzoic acid (3,3′‐H2ADB) yielded five novel metal‐organic frameworks. All the 3,3′‐ADB2– anions got oxidized into 3,3′‐AO2DB2– and 3,3′‐AODB2– under solvothermal conditions. Compound 1 has a 3D 6‐connected pcu architecture based on [Mn3(COO)6] SBU. Compound 2 exhibits 3D threefold interpenetrating framework based on paddlewheel [Mn2(COO)4] SBU with 41263 topological configuration. Compound 3 bears zigzag double chains, which are then connected by π–π stacking interactions into 2D porous structure. Compound 4 features 2D network with self‐penetrating feature. Compound 5 exhibits a fivefold interpenetrating architecture with dia type. Magnetic measurements show that 1, 2 and 5 exhibit antiferromagnetic behavior. In addition, compound 3 displays significant adsorption towards methylene blue in aqueous solution. Thermogravimetric analyses for 1–5 and the luminescence properties of 3 and 4 have also been investigated.

Cationic bipy induced the three dimensional supramolecules based on azoxybenzene tetracarboxylate: Structures and NIR luminescence property

Series of Ln(III) coordination polymers, namely, {[Ln(Oaobtc)(H2O)4]·Hbipy·H2O}n(H4Oaobtc = oxidation azoxybenzene - 2, 2′, 3, 3′-tetracarboxylic acid, bipy = 4,4′-bipyridine, and Ln = Pr(1), Nd(2), Ho(3), Er(4), Yb(5), respectively) have been designed, afforded and luminescence characterized systematically. The family coordination polymers are nearly isostructural sets, featuring one dimensional (1D) zigzag double chain edifice structure, with cationic Hbipy+ guest being located along two sides. These 1D chains are interlinked into 2D network, and are further extended into 3D supramolecular architecture through hydrogen bonding interactions from the cationic Hbipy+ moiety. The photo luminescence emission spectra of polymer 1 and 4 are based on the H4aobtc acid ligand, while 2, 3 and 5 display the emissions originated from characteristic f-f transitions of Ln(III) ions within near-infrared (NIR) regions.

Supramolecular Interactions Modulating Electrical Conductivity and Nanoprocessing of Copper-Iodine Double-Chain Coordination Polymers.

Two coordination polymers (CPs), based on Cu(I)-I double zig-zag chains bearing isonicotinic acid or 3-chloroisonicotinic acid as terminal ligands with molecular recognition capabilities, have been synthesized and fully characterized. Both compounds present extended networks with supramolecular interactions directed by the formation of H-bonds between the complementary carboxylic groups, giving supramolecular sheets. The chloro substituent allows establishing additional Cl···Cl supramolecular interactions that reinforce the stability of the supramolecular sheets. These CPs are semiconductor materials; however, the presence of chlorine produces slight changes in the I-Cu-I chains, generating a worse overlap in the Cu-I orbitals, thus determining a decrease in its electrical conductivity value. These experimental results have also been corroborated by theoretical calculations using the study of the morphology of the density of states and 3D orbital isodensities, which determine that conductivity is mostly produced through the Cu-I skeleton and is less efficient in the case of the chloro derivative compound. A fast and efficient bottom-up approach based on the self-assembly of the initial building blocks and the low solutibility of these CPs has proved very useful for the production of nanostructures.

Increasing Structural Dimensionality of Alkali Metal Fluoridotitanates(IV).

Reactions between AF (A = Li, Na, K, Rb, Cs) and TiF4 (with starting n(AF):n(TiF4) molar ratios in the range from 3:1 to 1:3) in anhydrous hydrogen fluoride yield [TiF6]2-, [TiF5]-, [Ti4F19]3-, [Ti2F9]-, and [Ti6F27]3- salts. With the exception of the A2TiF6 compounds, which consist of A+ cations and octahedral [TiF6]2- anions, all of these materials arise from the condensation of TiF6 units. The anionic part in the crystal structures of A[TiF5] (A = K, Cs) and A[TiF5]·HF (A = Na, K, Rb) is composed of infinite ([TiF5]-)∞ chains built of TiF6 octahedra sharing joint vertices. Each structure shows a slightly different geometry of the ([TiF5]-)∞ chains. The crystal structure of Na[Ti2F9]·HF is constructed from polymeric ([Ti2F9]-)∞ anions that appear as two parallel infinite zigzag chains comprising TiF6 units, where each TiF6 unit of one chain is connected to a TiF6 unit of the other chain through a shared fluorine vertex. Slow decomposition of single crystals of K4[Ti8F36]·8HF and Rb4[Ti8F36]·6HF ( Shlyapnikov , I. M. ; et al. Chem. Commun. 2013 , 49 , 2703 ) leads to the formation of [Ti2F9]- (Rb) and [Ti6F27]3- (K, Rb) salts. The former displays the same ([Ti2F9]-)∞ double chain as in Na[Ti2F9]·HF, while the anionic part in the latter, ([Ti6F27]3-)∞, represents the first example of a three-dimensional network built of TiF6 octahedra. The ([Ti6F27]3-)∞ anion was also found in [H3O]3[Ti6F27]. The crystal structure determination of Cs3[Ti4F19] revealed a new type of polymeric fluoridotitanate(IV) anion, ([Ti4F19]3-)∞. Similar to the ([Ti2F9]-)∞ anion, it is also built of zigzag double chains comprising TiF6 units. However, in the former there are fewer connections between TiF6 units of two neighboring chains than in the latter.

Smart composite films of nanometric thickness based on copper-iodine coordination polymers. Toward sensors.

One-pot reactions between CuI and methyl or methyl 2-amino-isonicotinate give rise to the formation of two coordination polymers (CPs) based on double zig-zag Cu2I2 chains. The presence of a NH2 group in the isonicotinate ligand produces different supramolecular interactions affecting the Cu-Cu distances and symmetry of the Cu2I2 chains. These structural variations significantly modulate their physical properties. Thus, both CPs are semiconductors and also show reversible thermo/mechanoluminescence. X-ray diffraction studies carried out under different temperature and pressure conditions in combination with theoretical calculations have been used to rationalize the multi-stimuli-responsive properties. Importantly, a bottom-up procedure based on fast precipitation leads to nanofibers of both CPs. The dimensions of these nanofibres enable the preparation of thermo/mechanochromic film composites with polyvinylidene difluoride. These films are tens of nanometers in thickness while being centimeters in length, representing smaller thicknesses so far reported for thin-film composites. This nanomaterial integration of CPs could represent a source of alternative nanomaterials for opto-electronic device fabrication.

Point sets with many non-crossing perfect matchings

The maximum number of non-crossing straight-line perfect matchings that a set of n points in the plane can have is known to be O(10.0438n) and Ω⁎(3n). The lower bound, due to García, Noy, and Tejel (2000), is attained by the double chain, which has Θ(3n/nΘ(1)) such matchings. We reprove this bound in a simplified way that uses the novel notion of down-free matchings. We then apply this approach to several other constructions. As a result, we improve the lower bound. First we show that the double zigzag chain with n points has Θ⁎(λn) non-crossing perfect matchings with λ≈3.0532. Next we analyze further generalizations of double zigzag chains – double r-chains. The best choice of parameters leads to a construction that has Θ⁎(νn) matchings with ν≈3.0930. The derivation of this bound requires an analysis of a coupled dynamic-programming recursion between two infinite vectors.

A series of anionic host coordination polymers based on azoxybenzene carboxylate: structures, luminescence and magnetic properties.

A series of coordination polymers {[Ln(aobtc)(H2O)4]·Hbipy·H2O}n (H4aobtc = azoxybenzene-2,2',3,3'-tetracarboxylic acid, bipy = 4,4'-bipyridine, and Ln = Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Er(6)) have been synthesized and characterized systematically. The cationic Hbipy+ guest incorporated polymers are isostructural sets, featuring a one-dimensional (1D) zigzag double chain edifice composed of binuclear clusters [Ln2(H4aobtc)2], with the Hbipy+ guest being located on two sides. These 1D chains are further interlinked into a 2D layer structure, and further extended into a 3D framework through hydrogen bonding interactions. The luminescence emission spectra of polymers 2 and 3 are based on the H4aobtc acid ligands, while 1 and 4 display the characteristic f-f transitions of Ln(iii) ions. Magnetic measurements revealed the presence of ferromagnetic behavior in polymer 3. The magnetic behaviors of 4 and 6 are ascribed to the depopulation of the Stark levels and/or weak antiferromagnetic interactions within MOFs at lower temperature. Slow relaxation is observed through the alternating-current susceptibility measurements for 5 at lower temperature, and the coexistence of weak ferromagnetism corresponding to the spin-canting-like behavior.

Anisotropic magneto-transport and magnetic properties of low-temperature phase of TaTe2

TaTe2 is a quasi-2D charge density wave (CDW) compound with distorted-1T–type structure exhibiting double-zigzag chains. Here we report the Fermi surface topology of a low-temperature phase of TaTe2 (LT-TaTe2) by anisotropic magneto-transport and magnetic measurements on high-quality single crystals. An anomalous large linear magnetoresistance up to 140% at 3 K in 9 T was observed, suggesting the existence of a small Fermi pocket in the Dirac cone state in quantum transport models. Moreover, strong magnetic anisotropy was observed for B⊥(001) and B∥(001). Angle-dependent magnetoresistance and de Hass-van Alphen oscillations suggest the anisotropy of the normal Fermi surface and the small Fermi pocket in Dirac cone state.

Crystal Structure and Thermal Property of 1-Ethyl Acetate Pyridinium Ionic Liquid

[EAPy][PF6] Pyridinium ionic liquid was synthesized by two-step process: introduction of one ethyl acetate group and anions metathesis. Additionally, single crystals of the IL was first obtained by solvent-evaporation method in growth systems. [EAPy][PF6] crystallizes in the monoclinic space group C2/c, with unit cell parameters a =22.748 Å, b =6.204 Å, c =18.552 Å, β =92.66°, z =8,V=2615(3) Å, Dc =1.58 Mg/m3 and F(000)=1264. In its supramolecular structure, the double zigzag chains are formed by hydrogen bonds and these [P(1)F6]- and [P(2)F6]- anions are sandwiched respectively by pyridinium rings and ethyl acetate groups in the packing pattern. Moreover, [EAPy][PF6] exhibits relatively high thermal stability and obvious supercooling during the cooling process, which makes pyridinium IL difficult to crystallize.

Crystal chemistry and X-ray diffraction patterns for Co(NixZn1−x)Nb4O12(x= 0.2, 0.4, 0.6, 0.8)

X-ray reference powder patterns and structures have been determined for a series of cobalt-, nickel- and zinc-containing niobates, Co(NixZn1−x)Nb4O12(x= 0.2, 0.4, 0.6, 0.8). The Co(NixZn1−x)Nb4O12series crystallize in the space group ofPbcn, which is of the disordered columbite-type structure (α-PbO2). The lattice parameters range froma= 14.11190(13) to 14.1569(3) Å,b= 5.69965(6) to 5.71209(13) Å,c= 5.03332(5) to 5.03673(11) Å, andV= 404.844(8) to 407.296(17) Å3fromx= 0.8 to 0.2, respectively. Co(NixZn1−x)Nb4O12contains double zig-zag chains of NbO6octahedra and single chain of (Ni,Zn,Co)O6octahedra run parallel to thebc-plane. Within the same chain the NbO6octahedra share edges, while the adjacent NbO6chains are joined to each other through common oxygen corners. These double NbO6chains are further linked together along the [100]-direction through another (Co,Ni,Zn)O6units, via common oxygen corners. The edge-sharing (Co,Ni,Zn)O6also forms zig-zag chains along thec-axis. Powder X-ray diffraction patterns of this series of compounds have been submitted to be included in the Powder Diffraction File.

Syntheses, Structural, and Luminescence Study on a New 1D Zn(II) Complex With Hydrazine-Based Ligand

A new Zn-based complex with chemical formulae {[Zn2(L)2(4,4′-bipy)]·DMF}n (1) (H2L = 3,5-dibromosalicylaldehyde salicylhydrazone; 4,4′-bipy = 4,4′-pyridine), has been synthesized and structurally characterized. 1 shows an interesting double zigzag chain along the b axis. Furthermore, the luminescence property of compound 1 has been investigated.