One-dimensional Helical Chain Research Articles

N-Ligands mediated Co(Ⅱ) coordination polymer incorporating 5-hydroxyisophthalic acid: Syntheses, structures, and theoretical calculations

The coordination polymer, [Co(L)(hip)]n (1), (L = 11-fluoro-pyridine[3,2-a:2',3'-c]phenazine and H2hip = 5-hydroxyisophthalic acid), has been successfully synthesized under hydrothermal condition. Complex 1 crystallizes in tetragonal, space group P43212 and the asymmetric unit consists of one Co(II) ion, one hip2- anion and one ligand L. The binuclear [Co2(L)2(hip)4]4- second building unit is formed by the coordination of four different hip2- anions and two Co(L) moieties. The adjacent Co(Ⅱ) centers are connected by the bridging hip2- anions to form a one-dimensional helical chain. Finally, a three-dimensional structure is formed by the self-assembly of the coordination bond between the Co centers and the hip2- anions. The powder X-ray diffraction, thermal analysis, IR analysis, UV-Vis absorption spectrum, photoluminescent properties and theoretical calculation for complex 1 are straight displayed. KEY WORDS: Co(Ⅱ), 5-hydroxyisophthalic acid, Coordination polymer, Crystal structure Bull. Chem. Soc. Ethiop. 2024, 38(4), 877-887. DOI: https://dx.doi.org/10.4314/bcse.v38i4.5

Synthesis of 3-D co(II)-oxonate colorimetric probe for selective detection of isopropanol, Co2+, and MnO4 –

A coordination polymer (CP) based on Co(II), {[Co(Ox)(H2O)3] · 2H2O} n (KA@CP2_ARS), has been synthesized using 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene (Timb) and potassium oxonate (OxK) at room temperature which was examined by single-crystal X-ray diffraction. KA@CP2_ARS contains a one-dimensional (1-D) helical chain that is extended through hydrogen-bonding interactions to form two-dimensional (2-D) and three-dimensional (3-D) supramolecular networks. KA@CP2_ARS demonstrates highly selective luminescent performance for IPA, Co2+, MnO4 –, and uric acid with detection limits of 0.214, 0.16, 0.076, and 0.65 ppm, respectively, among the screened analytes. KA@CP2_ARS displays strong photocatalytic activities for degrading 88.6% of methyl violet dye under ultraviolet irradiation.

Assembly of Lanthanide-Containing 3D [MnMo9O32]6--Based Metal-Organic Frameworks and Oxidative Desulfurization Performance.

Lanthanide-containing polyoxometalate-based metal-organic frameworks (POMOFs) not only enjoy intriguing architectures but also have good application prospects as catalysts. Herein, three novel three-dimensional (3D) POMOFs with the formulas of {H[Ln3(2,6-pydc)2(H2O)10(MnMo9O32)]·2H2O}n (Ln = La(1), Pr(2), Nd(3)) have been synthesized based on Waugh-type [MnMo9O32]6- anions and pyridine-2,6-dicarboxylate (2,6-H2pydc). Compounds 1-3 are isomorphic, and there are two kinds of one-dimensional (1D) helical chains with opposite handedness staggered into two-dimensional (2D) layers. Interestingly, the coordinated L- and R-[MnMo9O32]6- anions are encapsulated in 1D chains with the same chirality and are further expanded into 3D structures. The catalytic tests indicate that compounds 1-3 exhibit high-efficiency heterogeneous catalytic activity in the oxidative desulfurization reaction for catalyzing the oxidation of sulfides to sulfoxides using tert-butyl hydrogen peroxide (TBHP) as the oxidant. Moreover, a series of control experiments have been conducted to investigate the influence of various parameters such as temperature, time, solvent, catalyst, and substrate on the reaction. Significantly, compound 2, as an example, exhibits good reusability and structural stability in the oxidative desulfurization reaction. It is worth noting that investigations on the oxidative desulfurization of [MnMo9O32]6- anions are scarce. Moreover, their electrochemical properties are also explored.

Coordination-Driven Self-Assembly of Complexes Constructed from Two Helical Ligands: Synthesis, Structures, and Selective Gas Adsorption Properties.

Two helical ligands (L1 and L2) were designed and synthesized by a Schiff base condensation reaction. Eight complexes, {[Zn(L1)I2]·H2O}n (1), [Cd2(L1)2I4(CH3OH)2] (2), [Hg2(L1)2I4] (3), [Ag(L1)NO3]n (4), [Ag2(L1)2(NO3)2DMSO]·H2O (5), {[Zn2(L2)2Cl4]·2CHCl3}n (6), {[Ag(L2)]·NO3}n (7), and {[Ag(L2)NO3]·CH3OH}n (8), were synthesized and characterized based on these two ligands. The crystal structures show that both Schiff base compounds exist as racemic ligands with equal amounts of P- and M-helicity, and the assembly of these racemic ligands with metal ions can lead to homochiral or heterochiral complexes via a chiral self-recognition or self-discrimination process. Complexes 2, 3, and 5 exist as heterochiral metallomacrocycles with a figure-eight conformation. Complexes 1, 6, and 8 exist as one-dimensional (1D) homochiral helical chain coordination polymers, while complexes 4 and 7 exist as 1D heterochiral helical chain coordination polymers. Furthermore, gas and vapor adsorption measurements show that all of the synthesized complexes exhibit good selective adsorption capacities toward methanol and ethanol vapor over N2, H2, and O2.

A new heteroleptic cuprous polymer constructed by a cyanopyridine ligand exhibiting a supramolecular framework structure and luminescence.

Luminescent cuprous complexes are of great importance among coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title heteroleptic cuprous polymer solvate, catena-poly[[[(9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane)-κ2P,P'](μ-pyridine-3-carbonitrile-κ2N1:N3)copper(I)] hexafluorophosphate dichloromethane trisolvate], {[Cu(C6H4N2)(C39H32OP2)]PF6·3CH2Cl2}n, conventionally abbreviated as {[Cu(3-PyCN)(Xantphos)]PF6·3CH2Cl2}n, where Xantphos and 3-PyCN represent (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane) and pyridine-3-carbonitrile, respectively, has been described. In this polymer solvate, the asymmetric unit consists of three dichloromethane solvent molecules, a hexafluorophosphate anion and a polymeric heteroleptic cuprous complex cation, in which the cuprous centre is in a CuP2N2 tetrahedral coordination and is coordinated by two P atoms from the Xantphos ligand and two N atoms from two 3-PyCN ligands (the pyridyl and cyano N atoms). It is through the connection of the μ2-bridging 3-PyCN ligand that these cuprous centres are linked into a one-dimensional helical chain structure. The chains are further assembled through C-H...π interactions to form a supramolecular metal-organic framework containing solvent-accessible channels. The UV-Vis absorption and photoluminescence properties of this heteroleptic cuprous polymer have been studied on as-synthesized samples. Its luminescence emission should mainly originate from the metal-to-ligand charge transfer excited state.

Prevalence of trivial zero-energy subgap states in nonuniform helical spin chains on the surface of superconductors

Helical spin chains, consisting of magnetic (ad-)atoms, on the surface of bulk superconductors are predicted to host Majorana bound states (MBSs) at the ends of the chain. Here, we investigate the prevalence of trivial zero-energy bound states in these helical spin chain systems. First, we show that the Hamiltonian of a helical spin chain on a superconductor can be mapped to an effective Hamiltonian reminiscent of a semiconductor nanowire with strong Rashba spin-orbit coupling. In particular, we show that a varying rotation rate between neighbouring magnetic moments maps to smooth non-uniform potentials in the effective nanowire Hamiltonian. Previously it has been found that trivial zero-energy states are abundant in nanowire systems with smooth potentials. Therefore, we perform an extensive search for zero-energy bound states in helical spin chain systems with varying rotation rates. Although bound states with near zero-energy do exist for certain dimensionalities and rotation profiles, we find that zero-energy bound states are far less prevalent than in semiconductor nanowire systems with equivalent non-uniformities. In particular, utilising varying rotation rates, we do not find zero-energy bound states in the most experimentally relevant setup consisting of a one-dimensional helical spin chain on the surface of a three-dimensional superconductor, even for profiles that produce near zero-energy states in equivalent one- and two- dimensional systems. Although our findings do not rule them out, the much reduced prevalence of zero-energy bound states in long non-uniform helical spin chains compared with equivalent semi-conductor nanowires, as well as the ability to measure states locally via STM, should reduce the experimental barrier to identifying MBSs in such systems.

A new chiral rare-earth organic framework constructed by tartaric acid: synthesis, structural, thermal investigations and optical properties.

Hydrothermal reactions of rare-earth cerium with L-tartaric acid afford a new coordination polymer, namely, poly[[triaqua(μ4-L-tartrato)cerium(III)] chloride], {[Ce(C4H4O6)(H2O)3]Cl}n, (1). The structure was determined by single-crystal X-ray diffraction analysis and further characterized by IR and UV-Vis spectroscopy, powder X-ray diffraction and thermogravimetric analysis. Single-crystal X-ray diffraction analysis revealed that the compound is a new two-dimensional (2D) double-layered structure with one-dimensional left-handed helical chains. The different intermolecular interactions were confirmed using Hirshfeld surface analysis and molecular fingerprint plots. Molecular 2D fingerprint plots quantify the different interactions and highlight that H...H (24.8%), H...O/O...H (26.3%), Cl...H/H...Cl (19.6%), O...O (13.8%) and Ce...O/O...Ce (13.6%) interactions account for 99.8% of all contacts. Additionally, the photoluminescence properties of the compound were investigated in the solid state.

Prediction of Large Second Harmonic Generation in the Metal-Oxide/Organic Hybrid Compound CuMoO3(p2c)

Noncentrosymmetric hybrid framework (HF) materials are an important system in discovering new practical second-order nonlinear optical materials. We calculated the second harmonic generation (SHG) response of a noncentrosymmetric (NCS) organic–inorganic HF compound, CuMoO3(p2c) (p2c = pyrazine-2-carboxylate) to find that it exhibits the largest SHG response among all known NCS HF materials with one-dimensional helical chains. Further atom response theory analysis revealed that the metal atoms Cu and Mo contribute much more strongly than do nonmetal atoms in determining the strength of the SHG response, which is a novel example in nonlinear optical materials known to date.

Rashba effect and flat band property in one-dimensional helical Se atomic chain

Tuning the electronic properties of low-dimensional materials is helpful in building nano electronic devices. Here, we investigate the structural and electronic structures of one-dimensional helical Se atomic chain by using first-principles calculations. Our results show that this structure has a much lower energy than the one with a straight-line structure. Our phonon calculations and <i>ab initio</i> molecular dynamics simulations suggest that this structure is both dynamically and thermally stable. The band structure shows that it is a semiconductor with a gap of about 2.0 eV and Rashba-type splitting near the <i>X</i> point. The helical structure is good for tuning the electronic properties by using strains. As a result, a 5% strain leads to a 20% change in the band gap while the Rashba energy offset is doubled. Moreover, we find that the valence band is a flat band, over which hole doping can induce ferromagnetism and the system becomes half-metallic. Further increasing the doping level can transform the system into a ferromagnetic metal. Such a strategy is then applied to one-dimensional helical Te atomic chain and similar results are obtained.

A Microporous MOF Constructed by Cross-Linking Helical Chains for Efficient Purification of Natural Gas and Ethylene

Natural gas (NG) and ethylene (C2H4) are two raw materials of significant value for manufacturing versatile fine chemicals and/or polymers, and thus the development of solid adsorbing agents such as metal-organic frameworks (MOFs) applied to their depuration is very crucial but remains highly challenging. In this research, we designed and synthesized a ligand containing mixed N and O coordination donors, which was solvothermally assembled with Cu(II) ions to generate a microporous MOF. X-ray crystallography revealed that the title MOF incorporates one-dimensional (1D) homochiral helical chains that are datively cross-linked to form open channels in the three-periodic coordination framework. Furthermore, the behaviors of C1-C2 hydrocarbons and carbon dioxide (CO2) adsorbed in the title MOF were systematically investigated, revealing its promising potential for the purification of both NG and C2H4. At 109 kPa and 298 K, the C2/methane (CH4), CO2/CH4, and acetylene (C2H2)/C2H4 adsorption selectivities are impressive, reaching as high as 62.9, 28.6, and 3.5, respectively. This work represents a unique MOF based on cross-linked homochiral helical chains exhibiting dual-function separation potentials for NG and C2H4 purifications.

Chalcogenic orbital density waves in the weak- and strong-coupling limit

Stimulated by recent works highlighting the indispensable role of Coulomb interactions in the formation of helical chains and chiral electronic order in the elemental chalcogens, we explore the p-orbital Hubbard model on a one-dimensional helical chain. By solving it in the Hartree approximation we find a stable ground state with a period-three orbital density wave. We establish that the precise form of the emerging order strongly depends on the Hubbard interaction strength. In the strong coupling limit, the Coulomb interactions support an orbital density wave that is qualitatively different from that in the weak-coupling regime. We identify the phase transition separating these two orbital ordered phases, and show that realistic values for the inter-orbital Coulomb repulsion in elemental chalcogens place them in the weak coupling phase, in agreement with observations of the order in the elemental chalcogens.

Isostructural Hg(II) halide coordination polymers: A comparison of powder XRD, IR, emission and Hirshfeld Surface Analysis

Three isomorphous mercury(II) halide coordination polymers [Hg(dpndc)X2]n (X = Cl, 1; Br, 2; I, 3) have been synthesized by the reactions of HgX2 salts with the semi-rigid N,N’-di(pyridin-3-yl)naphthalene-1,4-dicarboxamide (dpndc), which form one-dimensional (1D) helical chains. Stuctural comparisons with the other similar CPs indicate that their structural diversity is governed by the co-crystallized solvent molecules and the identity of the spacer ligands, whereas the role of the halide anions is not significant. Hirshfeld Surface Analysis revels that chlorine atom contributes more non-covalent interactions compared to the bromine and iodine atoms. Complexes 1 - 3 provide a unique opportunity to demonstrate that the powder X-ray diffraction (PXRD) pattern is better than IR and emission spectra to differentiate isomorphous mercury(II) halide CPs.

Ba2Ge2Te5: a ternary NLO-active telluride with unusual one-dimensional helical chains and giant second harmonic-generation tensors

The linear-optical and NLO properties of a ternary NLO-active telluride, Ba2Ge2Te5, were investigated systematically at the experimental and theoretical levels for the first time.

Fluorinated Biphenyldicarboxylate-Based Metal-Organic Framework Exhibiting Efficient Propyne/Propylene Separation.

A novel fluorinated biphenyldicarboxylate ligand of 3,3',5,5'-tetrafluorobiphenyl-4,4'-dicarboxylic acid (H2-TFBPDC) and its terbium metal-organic framework, {[Tb2(TFBPDC)3(H2O)]·4.5DMF·0.5H2O}n (denoted as JXNU-6), were synthesized. JXNU-6 exhibits a three-dimensional (3D) framework built from one-dimensional (1D) terbium carboxylate helical chains bridged by TFBPDC2- linkers. The 3D framework of JXNU-6 features 1D fluorine-lined channels. The gas adsorption experiments show that the activated JXNU-6 (JXNU-6a) displays distinct adsorption behavior for propyne (C3H4) and propylene (C3H6) gases. The effective removal of a trace amount of C3H4 from C3H6 was achieved by JXNU-6a under ambient conditions, which is demonstrated by the column-breakthrough experiments. The modeling studies show that the preferential binding sites for C3H4 are the exposed F atoms on the pore surface in 1D channels. The strong C-H···F hydrogen bonds between C3H4 molecules and F atoms of TFBPDC2- ligands dominate the host-guest interactions, which mainly account for the excellent C3H4/C3H6 separation performance of JXNU-6a. This work provides a strategy for specific recognition toward C3H4 over C3H6 through the C-H···F hydrogen bond associated with the fluorinated organic ligand.

CFA-18: a homochiral metal-organic framework (MOF) constructed from rigid enantiopure bistriazolate linker molecules.

In this work, we introduce the first enantiopure bistriazolate-based metal-organic framework, CFA-18 (Coordination Framework Augsburg-18), built from the R-enantiomer of 7,7,7',7'-tetramethyl-6,6',7,7'-tetrahydro-3H,3'H-5,5'-spirobi[indeno[5,6-d]-[1,2,3]triazole] (H2-spirta). The enantiopurity and absolute configuration of the new linker were confirmed by several chiroselective methods. Reacting H2-spirta in hot N,N-dimethylformamide (DMF) with manganese(ii) chloride gave CFA-18 as colorless crystals. The crystal structure with the composition [Mn2Cl2(spirta)(DMF)2] was solved using synchrotron single-crystal X-ray diffraction. CFA-18 shows a framework topology that is closely related to previously reported metal-azolate framework (MAF) structures in which the octahedrally coordinated manganese(ii) ions are triazolate moieties, and the chloride anions form crosslinked one-dimensional helical chains, giving rise to hexagonal channels. In contrast to MAFs crystallizing in the centrosymmetric space group R3[combining macron], the handedness of the helices found in CFA-18 is strictly uniform, leading to a homochiral framework that crystallizes in the trigonal crystal system within the chiral space group P3121 (no. 152).

Charge Mobility and Recombination Mechanisms in Tellurium van der Waals Solid.

Trigonal tellurium is a small band gap elemental semiconductor consisting of van der Waals bound one-dimensional helical chains of tellurium atoms. We study the temperature dependence of the charge carrier mobility and recombination pathways in bulk tellurium. Electrons and holes are generated by irradiation of the sample with 3 MeV electrons and detected by time-resolved microwave conductivity measurements. A theoretical model is used to explain the experimental observations for different charge densities and temperatures. Our analysis reveals a high room temperature mobility of 190 ± 20 cm2 V–1 s–1. The mobility is thermally deactivated, suggesting a band-like transport mechanism. According to our analysis, the charges predominantly recombine via radiative recombination with a radiative yield close to 98%, even at room temperature. The remaining charges recombine by either trap-assisted (Shockley–Read–Hall) recombination or undergo trapping to deep traps. The high mobility, near-unity radiative yield, and possibility of large-scale production of atomic wires by liquid exfoliation make Te of high potential for next-generation nanoelectronic and optoelectronic applications, including far-infrared detectors and lasers.

A hydrogen-bonded inorganic-organic network with noncentrosymmetric structure exhibiting second-order nonlinear optical response

An inorganic-organic hybrid compound (H2DPA)2(SiF6) (1) constructed from the di(pyridine-4-yl)amine (DPA) ligands and octahedral SiF62− anions was presented. The protonated H2DPA cations and SiF62− anions are linked by the NH⋯F hydrogen bonds to give a one-dimensional (1D) helical chain, which is further linked by the NH⋯F hydrogen bonds to generate a three-dimensional (3D) framework featuring helical chains. Compound 1 crystallizes in an acentric space group and exhibits a phase-matchable second-harmonic-generation (SHG) response of 1.4 times that of potassium dihydrogen phosphate (1.4 × KDP). The nonlinear organic ligand with inherent dipole and the distorted [SiF6] octahedra, as well as the helical chains in a parallel packing mode contribute the SHG activity for 1.

Intrinsic two-dimensional states on the pristine surface of tellurium

Using a tight-binding description, we show how the zero-dimensional state bound to the edge of a single one-dimensional helical chain of tellurium atoms evolves into two-dimensional states on the c-axis surface of the three-dimensional trigonal bulk. We give an effective Hamiltonian description of its dispersion in k-space by exploiting confinement to a virtual bilayer, and elaborate on the diminished role of spin-orbit coupling. These previously-unidentified intrinsic gap-penetrating surface bands were neglected in the interpretation of seminal experiments, where two-dimensional transport was otherwise attributed to extrinsic accumulation layers.

The Nature of Bonding in Bulk Tellurium Composed of One-Dimensional Helical Chains.

Bulk tellurium (Te) is composed of one-dimensional (1D) helical chains which have been considered to be coupled by van der Waals (vdW) interactions. However, on the basis of first-principles density functional theory calculations, we here propose a different bonding nature between neighboring chains: i.e., helical chains made of normal covalent bonds are connected together by coordinate covalent bonds. It is revealed that the lone pairs of electrons of Te atoms participate in forming coordinate covalent bonds between neighboring chains, where each Te atom behaves as both an electron donor to neighboring chains and an electron acceptor from neighboring chains. This ligand-metal-like bonding nature in bulk Te results in the same order of bulk moduli along the directions parallel and perpendicular to the chains, contrasting with the large anisotropy of bulk moduli in vdW crystals. We further find that the electron effective masses parallel and perpendicular to the chains are almost the same as each other, consistent with the observed nearly isotropic electrical resistivity. It is thus demonstrated that the normal/coordinate covalent bonds parallel/perpendicular to the chains in bulk Te lead to a minor anisotropy in structural and transport properties.

A mesoporous metal-organic framework: Potential advances in selective dye adsorption

A new metal-organic framework based on manganous (II) ions and a paddle wheel ligand, H3[Mn3O3(BTB)] (Mn-BTB, HBTB = 1,3,5-tris(4-carboxyphenyl)benzene acid), was synthesized and structurally characterized. Mn-BTB was formed via self-assembly of one-dimensional (1D) helical chains interconnected through the carboxyl groups of the tripodal ligand HBTB to generate a 3D, extended network with a nanotube-like architecture and aperture size of 18.22 Å × 16.40 Å. The 2-fold self-interpenetration significantly enhanced the stability of the framework, although it minimized the empty space to some extent. Mn-BTB contains an accessible volume of 3143.6 Å3 with a 47.1% porosity, which allowed the adsorption of large dye molecules. Cationic dyes (methylene blue (MB) and rhodamine B (RhB)) and an anionic dye (methyl orange (MO)) were examined for selective dye adsorption on Mn-BTB. Mn-BTB with an anionic skeleton was beneficial for the selective adsorption of cationic dyes.