Ladder Chain Research Articles

Reversible stimulus-responsive coordination polymers mainly involving conversion between the lone-pair–π and cation–π interactions

A new 3-position substituted imidazo[1,2-a]pyridine ligand, 4-(2-chloroimidazo[1,2-a] pyridine-3-carboxamido)phthalic acid (H2L), was conveniently synthesized and acts as a three-connecting T-shaped building block. Based on this ligand, two isostructural coordination polymers, [ML(H2O)] n (M = Zn (1) and Co (2)) with a rare one-dimensional (1D) ladder-like chain structure, were solvothermally synthesized and structurally characterized. There exist hydrogen bond and lone-pair–π interactions between two adjacent ladder chains. Compared to the H2L ligand, coordination polymer 1 reveals a blue-shifted emission stemming from ligand-to-metal charge transfer, meanwhile, coordination polymer 2 presents a dominant antiferromagnetism. Interestingly, the carboxylate anion (COO−) in coordination polymers 1 and 2 could be protonated into carboxylic acid (–COOH), upon exposure to HCl vapor. As a result, coordination polymers 1 and 2 display reversible luminescent switching in the response to acid-base vapor stimuli, which mainly originates from the conversion between lone-pair–π and cation–π interactions mediated by the protonation-deprotonation processes. Such stimulus-responsive conversion between lone-pair–π and cation–π interactions is first reported in coordination polymers, and provides a promising approach to design and construct smart coordination polymer materials.

Syntheses, structures, and properties of four coordination polymers based on 2,7‐di(pyridin‐4‐yl)‐9H‐fluoren‐9‐one

Four coordination polymers (CPs), [Cd(2,7‐dpfo)2(NO3)2(CH3OH)]n (1), [Zn(2,7‐dpfo)(NO3)(CH3COO)]n (2), [Co(2,7‐dpfo)2(H2L)]n (3), and [Ni(2,7‐dpfo)2(H2L)]n (4) (where 2,7‐dpfo is 2,7‐di(pyridin‐4‐yl)‐9H‐fluoren‐9‐one and H4L is 1,1′:4′,1′′‐terphenyl‐4,2′,5′,4′′‐tetracarboxylic acid), were synthesized and structurally characterized. Compounds 1–4 were determined by elemental analyses, single crystal X‐ray diffraction analyses, powder X‐ray diffraction, infrared spectroscopy, and thermogravimetric analyses. Compound 1 displays a one‐dimensional (1D) zigzag chain structure, while compound 2 possesses a 1D ladder chain structure. Compounds 3 and 4 are isostructural and consist of 1D chains. The solid‐state luminescent properties of 1 and 2 and the magnetic properties of 3 and 4 were also investigated.

A self-penetrated three-dimensional zinc(II) coordination framework based on 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzoic acid and 1,3-bis[(imidazol-1-yl)methyl]benzene ligands: synthesis, structure and properties.

With the rapid development of metal-organic frameworks (MOFs), a variety of MOFs and their derivatives have been synthesized and reported in recent years. Commonly, multifunctional aromatic polycarboxylic acids and nitrogen-containing ligands are employed to construct MOFs with fascinating structures. 4,4',4''-(1,3,5-Triazine-2,4,6-triyl)tribenzoic acid (H3TATB) and the bidentate nitrogen-containing ligand 1,3-bis[(imidazol-1-yl)methyl]benzene (bib) were selected to prepare a novel ZnII-MOF under solvothermal conditions, namely poly[[tris{μ-1,3-bis[(imidazol-1-yl)methyl]benzene}bis[μ3-4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzoato]trizinc(II)] dimethylformamide disolvate trihydrate], {[Zn3(C24H12N3O6)2(C14H14N4)3]·2C3H7NO·3H2O}n (1). The structure of 1 was characterized by single-crystal X-ray diffraction, IR spectroscopy and powder X-ray diffraction. The properties of 1 were investigated by thermogravimetric and fluorescence analysis. Single-crystal X-ray diffraction shows that 1 belongs to the monoclinic space group Pc. The asymmetric unit contains three crystallographically independent ZnII centres, two 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzoate (TATB3-) anions, three complete bib ligands, one and a half free dimethylformamide molecules and three guest water molecules. Each ZnII centre is four-coordinated and displays a distorted tetrahedral coordination geometry. The ZnII centres are connected by TATB3- anions to form an angled ladder chain with large windows. Simultaneously, the bib ligands link ZnII centres to give a helical Zn-bib-Zn chain. Furthermore, adjacent ladders are bridged by Zn-bib-Zn chains to form a fascinating three-dimensional self-penetrated framework with the short Schläfli symbol 65·7·813·9·10. In addition, the luminescence properties of 1 in the solid state and the fluorescence sensing of metal ions in suspension were studied. Significantly, compound 1 shows potential application as a fluorescent sensor with sensing properties for Zr4+ and Cu2+ ions.

SYNTHESIS OF QUASI BAND LADDER TRANSFORMING HIGH ORDER FILTERS

The purpose of the work, the results of which are presented in the article, was to develop a computerized mathematical model of the ladder filter to study the features of the synthesis of matching chains of any order on its basis. To achieve this goal, all the synthesis tasks were solved, including the choice of the prototype, frequency transposition, calculation of the poles of the transfer function of the prototype, calculation of the poles of the transfer function of the filter, calculation of the reflection coefficient of the filter, the calculation of the input resistance of the filter, the implementation of the ladder chain by the Cauer method and denormalization of the values of the elements of the ladder chain. Modeling of characteristics of ladder filters of any high order with frequency characteristic of Chebyshev on the computer with 32-bit operating system is carried out. It is shown that the use of standard mathematics leads to a significant increase in the error of matching of loads at increasing the order of the chain. To increase the accuracy of calculations it is proposed to use software that allows implementing mathematical operations on variables with any length of the mantissa. There are computer libraries where numbers are presented in the form of string type variables and arithmetic operations are carried out on them according to school rules “ in a column ” . Once the calculations are completed, the strings are converted back to normal numbers. The article considers the application of the variant of BigNumber library for high level JavaScript language. To estimate the accuracy of the calculation it is proposed to apply the property of antimetric ladder structure. From the presented results of the calculation it follows that in order to obtain not less than 15 reliable digits after the decimal point for the parameters of the n-th order filter it is necessary to increase the length of the variable mantissa to the value 2n.

Diverse 1D chains supramolecular structures of N,N'-bis(3-pyridylmethyl)pyromellitic diimide and fluorescence iodide sensing.

Three diverse supramolecular compounds, {[3-pmpmd]}n(1), {H2[3-pmpmd]·2NO3-}n(2), {H2[3-pmpmd]·2tbb}n(3), (where 3-pmpmd was N,N'-bis(3-pyridylmethyl)pyromellitic diimide; tbb was tertiary butyl benzoic acid) were synthesized and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, and X-ray single-crystal structure analysis. The co-crystal anions affect their structural diversity. Compound 1 is a 1D stairway chain structure by perpendicular π⋯π interactions of pyromellitic diimide and the neighboring pyridine rings. Compound 2 is a typical 1D ladder chain structure by hydrogen bond of nitrate arranged in a parallel array. Compound 3 is a 1D zigzag chain structure of one 3-pmpmd and two tbb by parallel π⋯π interactions and hydrogen bond interactions. Thermal stabilities and fluorescence properties of all compounds were investigated. The solution of compound 2 in DMF can fluorescence sense for iodide ions by remarkably quenching fluorescence intensity.

Four congenetic zinc(II) MOFs from delicate solvent-regulated strategy: Structural diversities and fluorescent properties

Four new congenetic zinc(II) MOFs, namely [Zn5(bdcpp)3(DMF)(H2O)4]n·x(solvent) (1), [Zn2(bdcpp)(Hbdcpp)]n·y(solvent) (2), [Zn2(bdcpp)(DMF)(H2O)2]n (3), and [Zn2(bdcpp)(NMP)(H2O)2]n (4) (H4bdcpp = 2,6-bis(2′,4′-dicarboxylphenyl)pyridine, DMF = N,N'-dimethyl formamide, NMP = N-methyl-2-pyrrolidone), have been synthesized solvothermally with different solvent systems. Stabilized by Zn2(COO)4 paddle-wheel building blocks, the resulting MOFs 1–4 represent diverse structural features. Structurally, 1 is a rarely 3,4-c binodal 2D bilayered framework, 2 possesses a 4-c 2D (4,4) sql planar network accommodating two kinds of hetero chiral helix chains, 3 and 4 are isostructural 1D loop ladder chains except different solvent molecules occupying the axial terminals of Zn2(COO)4 paddle-wheels. This approach based on solvent-regulated strategy aiming to allow the structural fine-tuning provides a good role model in reticular chemistry. Complexes 1–3 display excellent solid-state photoluminescence stemming from the metal-to-ligand charge transfer or intraligand charge transmission.

Two coordination polymers constructed by 5-[(4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylic acid and 2,2'-bipyridine: syntheses, structures and luminescence properties.

Coordination polymers (CPs) have attracted increasing interest in recent years. In this work, two new CPs, namely poly[[aquabis(2,2'-bipyridine-κ2N,N'){μ3-5-[(4-carboxylatophenoxy)methyl]benzene-1,3-dicarboxylato-κ4O1,O1':O3:O5}(μ-formato-κ3O:O,O')dicadmium(II)] monohydrate], {[Cd2(C16H9O7)(HCO2)(C10H8N2)2(H2O)]·H2O}n (1), and poly[[(2,2'-bipyridine-κ2N,N'){μ3-5-[(4-carboxylphenoxy)methyl]benzene-1,3-dicarboxylato-κ4O1,O1':O3:O5}manganese(II)] sesquihydrate], {[Mn(C16H10O7)(C10H8N2)]·1.5H2O}n (2), have been prepared using the tricarboxylic acid 5-[(4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylic acid and 2,2'-bipyridine under hydrothermal conditions. CP 1 displays a two-dimensional layer structure which is further extended into a three-dimensional (3D) supramolecular structure via intermolecular π-π interactions, while CP 2 shows a different 3D supramolecular structure extended from one-dimensional ladder chains by intermolecular π-π interactions. In addition, the solid-state luminescence spectra of 1 and 2 were studied at room temperature.

Chain claims reserving methods in non-life insurance

Abstract Considering that the reliability of reserves valuation directly influences the financial strength of an insurance company, the main aim of this paper is to present a claims reserving estimation for a Romanian non-life insurer based on the most popular chain methods which are typically used in practice for the estimation of outstanding claims reserves in general insurance industry: Standard Chain Ladder and Munich Chain Ladder both on the claims incurred data and claims paid data. The tail development factors have been estimated based on the curve-fitting methods. The obvious advantage of these methods is represented by its simplicity of the practicality application. The results of the research under two chain claims reserving models reveal significant differences between the Standard Chain Ladder and Munich Chain Ladder with respect to the claims reserves level. Probably the Standard Chain Ladder based on paid method underestimates the outstanding loss liabilities and Standard Chain Ladder based on Incurred method overestimates the claims reserves. The claims reserves predictions under the Paid Munich Chain Ladder and Incurred Munich Chain Ladder are between the two Standard Chain Ladder outstanding loss liabilities estimates. The results of the tail extrapolation shown that the incorporation of the tail factors can have a significant impact on claims predictions.

Crystal Structure and Electrochemical Property of Tetrazole Complex of Copper [Cu(pta)2(NO3)2(H2O)2] (pta = 1-Phenyl-1H-tetrazole)

A new compound, [Cu(pta)2(NO3)2(H2O)2] (pta = 1-phenyl-1H-tetrazole) has been synthesized and characterized by IR, elemental analysis and single-crystal X-ray diffractions. X-ray structural analysis reveals that each Cu atom is coordinated by two pta molecules, two nitrate ions and two water molecules to form octahedral coordination geometry. O(1w) atoms of the water molecules serve as H-donor to interact with the nitrate oxygen atoms O(2), O(3) (H-acceptor) and form 1D hydrogen-bond ladder chains. These chains then, construct a 2D network layer via π-π stacking interactions between the five-membered ring of tetrazole and the six-membered ring of benzene. The 3D framework was constructed through the hydrogen bonds of C(7)-H(7A)····O(3). The behaviour of cyclic voltammetry of the compound on three-electrode cell showed an irreversible process.

Bifunctional coordination polymers as efficient catalysts for carbon dioxide conversion

The multidentate ligand H2L upon complexation with Zn (II) and Cd (II) provide a one‐dimensional polymeric networks. These coordination polymers (CPs) CP‐1 and CP‐2 containing Zn (II) and Cd (II) metals respectively are well characterized. The single crystal structural analysis confirms the formation of one‐dimensional coordination polymer with zigzag fashion in CP‐1 and ladder chain CP‐2. Both the CPs are applied as catalysts to synthesize various cyclic carbonates from epoxides and carbon dioxide. The catalysts are giving better conversion under solvent‐free and additive‐free condition using 10 bar CO2 and 100 °C as optimized pressure and temperature. The detailed kinetic experiments suggesting the first order kinetics, the energy of activation (Ea) is calculated for this catalytic conversion.

Aromatic Embrace Motifs for Bulk Supramolecular Polymers.

Frequently encountered in crystalline materials, aromatic embraces (AEs) are formed when arylated molecules interact through multiple concerted aromatic interactions. AEs are a robust motif that is suitable for the preparation of amorphous bulk supramolecular polymers (BSPs). Crystal engineering revealed that the polymorphic compound (PPh3 )(Cp)Fe(CO){CO(CH2 )5 CH3 } (Cp=cyclopentadienyl), known as FpC6 , assembled into various chain structures through several AE motifs. Upon melting, FpC6 always adopted the same AE motif, which extended into the corresponding embracing "ladder" chains. The resultant BSP displayed typical polymer behaviour, including the presence of a glass transition and viscoelasticity, which allowed the effect of thermal history on the polymerisation behaviour to be explored. The ladder chains formed by the AE remain assembled at temperatures of up to 130 °C and were able to effectively suppress crystallisation during cooling. The ability of the AE to form chains at high temperatures and suppress crystallisation is a new opportunity to advance the field of BSPs and supramolecular chemistry.

Ladder chain Cd-based polymer as a highly effective adsorbent for removal of Congo red

Developing of high effective and fast-rate adsorbent materials has been recently attracted intensive attentions all over the world due to organic dye polluted water treatment. However, few studies have been reported on the ultrahigh-capacity and fast-rate removal of Congo red. In this work, a new stable Cd-based coordination polymer exhibits excellent adsorption performance towards Congo Red. This ladder chain [Cd4(H2L)4(H2O)8(NDS)]n·3n(NDS) (I) (H2L = N1,N2-bis(pyridin-3-ylmethyl) ethane-1,2-diamine, 1,5-H2NDS = 1,5-naphthalene disulfonic acid) has been successfully synthesized by the hydrothermal reaction. At room temperature, the experimental adsorption capacity of coordination polymer (I) towards Congo red can reach up to 16,880 mg g−1 in 20 min (pH = 2.0–3.2), and its higher capacity and faster rate are all better than those in reported inorganic and metal-organic frameworks absorbents. The adsorption process is spontaneous and endothermic reaction, and fits well with the second-order kinetics, Langmuir and Scatchard isotherm adsorption models. The excellent adsorption performance of (I) towards Congo red is related to the strong electrostatic, various hydrogen bonding and π-π stacking interactions under acidic conditions.

Cadmium-Based Coordination Polymers from 1D to 3D: Synthesis, Structures, and Photoluminescent and Electrochemiluminescent Properties.

Cadmium-based coordination polymers, namely, {[Cd(HL)(L)] ⋅ HN(Et)3 }n (1), [Cd2 (L)2 (H2 O)5 ]n (2), [Cd(L)(phen)]n (3), [Cd(L)(2,2'-bpy)]n (4), [Cd(L)(4,4'-bpy)]n (5), [Cd(L)(bpp)]n (6), [Cd(L)(dpa)]n (7), {[Cd(L)(dpa)] ⋅ H2 O}n (8) (H2 L=4,4'-((p-tolylazanediyl)bis(methylene))dibenzoic acid, phen=1,10-phenanthroline, 2,2'-bpy=2,2'-bipyridine, 4,4'-bpy=4,4'-bipyridine, bpp=1,3-bis(4-pyridyl)propane, dpa=bis(4-pyridyl)amine) have been synthesized in hydro/solvothermal reactions. 1 is a 4-connect 3D network with an eightfold interpenetrating diamond topology. The 1D ladder chain structure of 2 was composed of the dinuclear [Cd2 (CO2 )4 ] subunit bridged with two L2- ligands. 3 shows a 1D double-chain with a channel formed by edging out the coordination water with the rigid co-ligand phen. Polymer 4 displays a 2D lamellar structure based on superseding the coordination water molecules by the rigid chelating auxiliary ligands 2,2'-bpy. By substituting the small molecules with a rigid bridging ligand 4,4'-bpy, a 2D undulating structure of 5 was built. Compounds 6 and 7 exhibit a 2D layer structure with a 4-connect (44 ⋅ 62 ) sql-net. Compound 8 presents a 3D architecture with a sixfold interpenetrating diamond topology. Through our construction strategy, versatile structures from 1D-3D have been rationally designed by controlling the process condition and rigid/flexible of N-donor spacers. Additionally, the photoluminescence, charge transfer, and electrochemical luminescence (ECL) properties of 1-8 have been demonstrated.

Synthesis, structure and magnetic properties of a new phase of cobalt(II) hydroxyl phosphate γ-Co2(PO4)(OH) with a warping two-legs ladder chain

A new phase of cobalt(II) hydroxyl phosphate γ-Co2(PO4)(OH) has been successfully synthesized through a conventional hydrothermal method. This compound crystallizes in the trigonal system of space group P31m, showing a warping two-legs spin ladder chain structure arranged in an unusual triangular network, in which a new spin-lattice of (3, 6, 4, 6)(4, 62) is built by magnetic Co2+ ions. Magnetic measurements indicate that γ-Co2(PO4)(OH) may show a spin-glass behavior at low temperature.

Ladder epochs and ladder chain of a Markov random walk with discrete driving chain

Abstract Let (Mn,Sn)n≥0 be a Markov random walk with positive recurrent driving chain (Mn)n≥0 on the countable state space 𝒮 with stationary distribution π. Suppose also that lim supn→∞Sn=∞ almost surely, so that the walk has almost-sure finite strictly ascending ladder epochs σn>. Recurrence properties of the ladder chain (Mσn>)n≥0 and a closely related excursion chain are studied. We give a necessary and sufficient condition for the recurrence of (Mσn>)n≥0 and further show that this chain is positive recurrent with stationary distribution π> and 𝔼π>σ1><∞ if and only if an associated Markov random walk (𝑀̂n,𝑆̂n)n≥0, obtained by time reversal and called the dual of (Mn,Sn)n≥0, is positive divergent, i.e. 𝑆̂n→∞ almost surely. Simple expressions for π> are also provided. Our arguments make use of coupling, Palm duality theory, and Wiener‒Hopf factorization for Markov random walks with discrete driving chain.

Four new Zn/Cd coordination polymers constructed by the asymmetrical N-heterocyclic rigid carboxylate: Synthesis, crystal structure, photoluminescence and sensing properties

Four new coordination polymers, namely, [Zn2(L)2(1,3-bdc)(H2O)2]n(1), [Cd2L2(Cl)2]n·0.5nH2O (2), [Cd2L2(adip)]n·2nH2O (3), and [CdLCl]n (4) were solvothermally synthesized by reaction of Zn(NO3)2·6H2O, CdCl2·H2O with an asymmetrical rigid N-heterocyclic carboxylatic acid (HL), where HL = 1-(4-carboxylphenyl)-3-(prazin-2-yl)-1H-1,2,4-triazole, 1,3-bdc = benzene- 1,3-dicarboxylic acid, H2adip = adipic acid, H2glu = glutaric acid. Compound 1 is a 1D ladder chain. Compound 2 is a (3,6)-connected network with the Point symbol of (42·6)2(44·62·88·10). Compound 3 displays a intriguing (3,3,4,4)-connected topological net with the Point symbol of (4·64·8)(4·72)(42·6·72·9)(42·6). Compound 4 presents a new (3,5)-connected topological net with the Point symbol of (3·4·5)(32·4·5·62·74). In addition, the thermal stabilities and photoluminescence properties of these compounds were also studied. Dramatically, compound 3 shows the high selectivity and sensitivity for Fe3+ cation via a luminescence quenching effect.

Four coordination polymers based on 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine: Syntheses, structures and properties

Four coordination polymers, [CuCl(cptpy)·2H2O]n(1), [Mn2Cl2(cptpy)2(phdat)H2O]n(2) and [Ln(cptpy)3]n (Ln = La (3), Pr (4)) (Hcptpy = 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine, phdat = 2,4-diamino-6-phenyl-triazine) have been hydrothermally synthesized and characterized by IR spectra, X-ray single-crystal diffraction, powder X-ray diffraction (PXRD), elemental analyses and thermogravimetric analyses (TGA). Compounds 1, 3 and 4 exhibit 2D or 3D structures comprising 1D linear chain connected by π…π stacking interactions. While, compound 2 contains two kinds of 1D chains, of which one is a linear chain and the other is a ladder chain, and further extends to 3D structure by π…π stacking and hydrogen bonding interactions. The electrochemical analysis shows that compound 1 has good catalytic activities for the reductions of both NaNO2 and H2O2, and is a potential catalytic material. Magnetic analysis indicates that compound 2 exhibits antiferromagnetic behavior.

Role of short-range correlation in facilitation of wave propagation in a long-range ladder chain

We extend a new method for generating a random chain, which has a kind of short-range correlation induced by a repeated sequence while retaining long-range correlation. Three distinct methods are considered to study the localization–delocalization transition of mechanical waves in one-dimensional disordered media with simultaneous existence of short and long-range correlation. First, a transfer-matrix method was used to calculate numerically the localization length of a wave in a binary chain. We found that the existence of short-range correlation in a long-range correlated chain can increase the localization length at the resonance frequency Ωc. Then, we carried out an analytical study of the delocalization properties of the waves in correlated disordered media around Ωc. Finally, we apply a dynamical method based on the direct numerical simulation of the wave equation to study the propagation of waves in the correlated chain. Imposing short-range correlation on the long-range background will lead the propagation to super-diffusive transport. The results obtained with all three methods are in agreement with each other.

Hybrid organic-inorganic connectivity of NdIII(pyrazine-N,N'-dioxide)[CoIII(CN)6]3- coordination chains for creating near-infrared emissive Nd(iii) showing field-induced slow magnetic relaxation.

A near-infrared emissive and magnetically anisotropic Nd(iii) complex is formed within a hybrid organic-inorganic {[NdIII(pzdo)(H2O)4][CoIII(CN)6]}·0.5(pzdo)·4H2O (1) (pzdo = pyrazine-N,N'-dioxide) ladder chain built of coexisting Nd-pzdo-Nd and Nd-NC-Co molecular bridges. 1 reveals two NdIII-centered properties, a field-induced slow magnetic relaxation of a single-ion origin with a thermal energy barrier of ΔE/kB = 51(2) K at Hdc = 1 kOe, and a near-infrared fluorescence sensitized by organic and inorganic linkers.

A new semiconducting coordination polymer consisting of copper(I)-iodide and 3-pyridinecarboxaldehyde

A new one-dimensional coordination polymer, [CuII(3-Py-CHO)]n (3-Py-CHO=3-pyridinecarboxaldehyde), consisting of an infinite copper(I)-iodide ladder chain and a pendant ligand, 3-Py-CHO, was prepared and structurally characterized using X-ray diffraction analysis. This material shows semiconducting properties with a relatively small activation energy, as shown by impedance measurements. We also estimated the electrical conductivity from a current-voltage (I-V) curve measured from a single crystal of the coordination polymer.