Linear Chain Structure Research Articles

Synthesis, crystal structures, and photocatalytic properties of two 2D supramolecular silver(I) coordination polymers derived from bis(1,2,4-triazole) and aromatic dicarboxylate ligands

Two silver(I)-mixed ligand coordination polymers (CPs), {[Ag(L)(Hmip)]·H2O} n (1) and {[Ag(L)]·0.5(DCTP)·H2O]} n (2) (H2mip = 5-methylisophthalic acid, H2DCTP = 2,5-dichloroterephthalic acid, and L = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl) have been hydrothermally synthesized and structurally characterized. Two CPs display 1D zigzag chain and linear chain structures, respectively. Furthermore, these 1D chains are extended into 2D supramolecular networks through hydrogen bonding interactions. The luminescence properties and photocatalytic behaviors of both CPs are reported.

Two Types of Lanthanide Coordination Polymers Based on a Homophthalate Ligand Exhibiting Luminescence and a Significant Magnetocaloric Effect

Two types of lanthanide coordination polymers based on homophthalic acid (H2HPA), one-dimensional {[Ln(HPA)(NO3)(H2O)2]·H2O}n (Ln = Eu (1); Gd (2); Tb (3); Dy (4)) and two-dimensional {[Ln2(HPA)3(H2O)2]·H2O}n (Ln = Eu (5); Gd (6); Tb (7); Dy (8)), were solvothermally synthesized. Compounds 1–4 show a one-dimensional (1D) linear chain structure consisting of a HPA2– linker and [Ln2] cluster unit. Compounds 4–8 are crystallographically isostructural and contain 1D lanthanide-carboxylate building units [Ln4(CO2)10]n built from the adjacent Ln3+ ions and carboxyl groups of the H2HPA ligands, which can further give two-dimensional layer structures via the link of HPA2–. The magnetic studies reveal that complexes 2 and 6 with isotropic Gd3+ ion exhibit significant cryogenic magnetocaloric effects with a maximum −ΔSm value of 35.58 and 35.41 J kg–1 K–1 at 2 K and 7 T, respectively. In addition, the solid-state photophysical properties of 1/5 and 3/7 respectively display strong characteristic Eu3+ and Tb3+ photol...

Two cadmium(II) fluorous coordination compounds tuned by different bipyridines.

Fluorine is the most electronegative element and can be used as an excellent hydrogen-bond acceptor. Fluorous coordination compounds exhibit several advantageous properties, such as enhanced high thermal and oxidative stability, low polarity, weak intermolecular interactions and a small surface tension compared to hydrocarbons. C-H...F-C interactions, although weak, play a significant role in regulating the arrangement of the organic molecules in the crystalline state and stabilizing the secondary structure. Two cadmium(II) fluorous coordination compounds formed from 2,2'-bipyridine, 4,4'-bipyridine and pentafluorobenzoate ligands, namely catena-poly[[aqua(2,2'-bipyridine-κ2N,N')(2,3,4,5,6-pentafluorobenzoato-κO)cadmium(II)]-μ-2,3,4,5,6-pentafluorobenzoato-κ2O:O'], [Cd(C7F5O2)2(C10H8N2)(H2O)]n, (1), and catena-poly[[diaquabis(2,3,4,5,6-pentafluorobenzoato-κO)cadmium(II)]-μ-4,4'-bipyridine-κ2N:N'], [Cd(C7F5O2)2(C10H8N2)(H2O)2]n, (2), have been synthesized solvothermally and structurally characterized. Compound (1) shows a one-dimensional chain structure composed of Cd-O coordination bonds and is stabilized by π-π stacking and O-H...O hydrogen-bond interactions. Compound (2) displays a one-dimensional linear chain structure formed by Cd-N coordination interactions involving the 4,4'-bipyridine ligand. Adjacent one-dimensional chains are extended into two-dimensional sheets by O-H...O hydrogen bonds between the coordinated water molecules and adjacent carboxylate groups. Moreover, the chains are further linked by C-H...F-C interactions to afford a three-dimensional network. In both structures, hydrogen bonding involving the coordinated water molecules is a primary driving force in the formation of the supramolecular structures.

Dynamic Mechanical Thermal Analysis and Rheological Properties of Synthesized Polypropylene Reactor Blends Using Homogeneous Binary Metallocene Catalyst

ABSTRACTA homogenous binary metallocene catalytic system comprising of isospecific rac-Me2Si(2-Me-4-Ph In)2ZrCl2(I) producing high molecular weight isotactic polypropylene and oscillating (2-Ph In)2ZrCl2(II) precursor producing low isotactic elastomer polypropylene at three varying molar ratios of two types of catalysts was used to synthesize polypropylene reactor blends. Dynamic mechanical thermal analysis and rheological properties along with molecular weight of synthesized polypropylene reactor blends were studied and correlations among these properties were established. It was found that molar ratio of catalysts is a significant factor in determination of molecular weight and its distribution. The produced polymers with unimodal molecular weight distribution showed intermediate modulus during dynamic mechanical thermal experiment, while the ones with bimodal molecular weight distribution exhibited a kind of phase separation at low temperature. Depending on strength of the developed structures, determined by the presence of interfacial connectors, the modulus could be adjusted. Origins of other types of relaxations and their differences for each type of the developed products were discussed in detail. From rheological results and particularly the relaxation curves, the characteristics of the chain structure of the synthesized reactor blends could be resolved. It was revealed that one of the synthesized polymers had long chain branches unlike the rest of the samples having linear chain structure.

Effect of ligand configurations, secondary Pb–O interactions and auxiliary ligands on Pb(ii)–mono/disulfonate complexes: syntheses, structures, and luminescence properties

Eight new Pb(II)–mono/disulfonate complexes, [Pb2(L1)2(H2O)]n (1), [Pb(L1)(2,2′-bipy)] (2), [Pb(L1)(phen)]·H2O (3), [Pb(L1)(H2O)]·0.5(4,4′-bipy) (4), [Pb(HL2)(H2O)3]n (5), [Pb4(L2)2(AcO)2(2,2′-bipy)(H2O)]n (6), [Pb3(L2)2(phen)(H2O)5]·2H2O (7) and [Pb(HL2)(4,4′-bipy)(H2O)]·H2O (8) (H2L1 = 2-hydroxy-5-chlorobenzenesulfonic acid, H3L2 = 2-hydroxy-5-chloro-1,3-benzenedisulfonic acid, phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, AcO− = acetate), have been synthesized by the reaction of a Pb(II) salt, mono- or disulfonate, with three N-heterocyclic auxiliary ligands and characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. With the primary Pb–O bonds, these eight complexes exhibit diverse dinuclear (2, 3, 4 and 8), hexanuclear (7), linear chain (1) and layer structures (5 and 6). The Pb(II) cations in these complexes present a hemidirected geometry, except for complex 6, in which the Pb(II) cations present rarely hemidirected and holodirected geometries in one system. Taking the secondary Pb–O bonds into account, chain structures for complexes 2 and 8 and layer motifs for complexes 1 and 4–7 are observed with the Pb(II) cations showing more intricate hemi- and holodirected geometries. Meanwhile, the disulfonate anions present more coordination sites to Pb(II) cations, thus leading to high-dimensional structures in comparison with the monosulfonate anions. Moreover, ligand configurations and the introduction of the N-heterocyclic auxiliary ligands also play important roles in modulating the structures of the Pb(II)–sulfonate complexes. Luminescence analyses indicate that complexes 6–8 present purple emission at 400, 397 and 399 nm at room temperature.

Swimming of a linear chain with a cargo in an incompressible viscous fluid with inertia

An approximation to the added mass matrix of an assembly of spheres is constructed on the basis of potential flow theory for situations where one sphere is much larger than the others. In the approximation, the flow potential near a small sphere is assumed to be dipolar, but near the large sphere it involves all higher order multipoles. The analysis is based on an exact result for the potential of a magnetic dipole in the presence of a superconducting sphere. Subsequently, the approximate added mass hydrodynamic interactions are used in a calculation of the swimming velocity and rate of dissipation of linear chain structures consisting of a number of small spheres and a single large one, with account also of frictional hydrodynamic interactions. The results derived for periodic swimming on the basis of a kinematic approach are compared with the bilinear theory, valid for small amplitude of stroke, and with the numerical solution of the approximate equations of motion. The calculations interpolate over the whole range of scale number between the friction-dominated Stokes limit and the inertia-dominated regime.

Experimental investigation of a linear-chain structure in the nucleus 14C

It is a well-known fact that a cluster of nucleons can be formed in the interior of an atomic nucleus, and such clusters may occupy molecular-like orbitals, showing characteristics similar to normal molecules consisting of atoms. Chemical molecules having a linear alignment are commonly seen in nature, such as carbon dioxide. A similar linear alignment of the nuclear clusters, referred to as linear-chain cluster state (LCCS), has been studied since the 1950s, however, up to now there is no clear experimental evidence demonstrating the existence of such a state. Recently, it was proposed that an excess of neutrons may offer just such a stabilizing mechanism, revitalizing interest in the nuclear LCCS, specifically with predictions for their emergence in neutron-rich carbon isotopes. Here we present the experimental observation of {\alpha}-cluster states in the radioactive 14C nucleus. Using the 10Be+{\alpha} resonant scattering method with a radioactive beam, we observed a series of levels which completely agree with theoretically predicted levels having an explicit linear-chain cluster configuration. We regard this as the first strong indication of the linear-chain clustered nucleus.

Syntheses, crystal structures, properties of metal coordination polymers based on a novel semi-rigid aromatic carboxylate ligand

A set of new metal coordination polymers constructed from a novel semi-rigid aromatic carboxylate ligand, namely, [M(L)(4PBI)(H2O)]n (M=Ni, Co and Cu for 1, 2 and 3, respectively) and [Cd(L)(4PBI)]n (4) (H2L=3-(1-carboxyethyl) benzoic acid; 4PBI=2-(pyridin-4-yl)-(1H)-benzoimidazole), have been synthesized by the hydrothermal reaction, which were characterized by element analyses, FT-IR, UV–Vis diffuse reflection spectra, X-ray single-crystal diffraction, powder X-ray diffraction, and thermogravimetric analyses (TGA). Complexes 1, 2 and 3 are iso-structural. They form a one-dimensional (1D) linear chain structure connected by semi-rigid aromatic anion and further assemble into a three-dimensional (3D) supramolecular framework by π⋯π stacking and hydrogen bonding interactions. Complex 4 possesses two bi-nuclear units and displays two-dimensional (2D) layer which can further extend to a 3D supramolecular architecture via hydrogen bonding and weak packing interactions. Moreover, the luminescent property of complex 4 was investigated in the solid state at room temperature.

Monopole excitation of the Hoyle state and linear-chain state inC12

Background: Two new $J^\pi=0^+$ states are recently observed around a few MeV above the Hoyle state (the second $0^+$ state in 12C). The characters of them are only poorly discussed in theory and are still mysterious. Purpose: I give for the first time a comprehensive understanding of the structures of the $0^+$ states by analyzing their wave functions, and discuss relationship with the Hoyle state, similarities, and differences between the states. Method: I extend a microscopic $\alpha$-cluster model called Tohsaki-Horiuchi-Schuck-R\"opke (THSR) wave function so as to incorporate $2\alpha+\alpha$ asymmetric configuration explicitly. The so-called $r^2$-constraint method to effectively eliminate spurious continuum components is also used. Results: The $0_3^+$ state is shown to have a very large squared overlap with a single configuration of the extended THSR wave function in an orthogonal space to the Hoyle state as well as to the ground state. The $0_4^+$ state has a maximal squared overlap with a single extended THSR wave function with an extremely prolately-deformed shape. Conclusions: The $0_3^+$ state appears as a family of the Hoyle state to have a higher nodal structure in the internal motions of the $3\alpha$ clusters, due to the orthogonalization to the Hoyle state. The $0_4^+$ state dominantly has a linear-chain structure, where the $3\alpha$ clusters move freely in a non-localized way, like a one-dimensional gas of the $3\alpha$ clusters.

Solvent- and metal-directed lanthanide-organic frameworks based on pamoic acid: observation of slow magnetization relaxation, magnetocaloric effect and luminescent sensing

Two types of lanthanide coordination polymers, namely, [Ln(PA)(NO3)(DMA)3] n (Ln=Gd (1), Dy (2), Eu (3), Tb (4)) (type I), and {[Ln2(PA)3(DMF)4]·2DMF} (Ln=Eu (5), Tb (6)) (type II) (PA=Pamoic acid, DMA=dimethylacetamide, DMF=N,N-dimethylformamide), have been synthesized by the reaction of Ln(NO3)3·6H2O with pamoic acid through layer diffusion method. These complexes were characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), thermogravimetric analysis (TGA), fluorescence and magnetic measurements. Solvents and lanthanide atoms in the reaction play an important role in controlling different structures. Type I demonstrated 1-D linear chain structure connected by Ln atoms and PA ligands. Type II exhibited non-interpenetrating 3-D 6-connected 43612 nets based on binuclear [Ln2(CO2)6(DMF)4] cores. Magnetic properties of complexes 1–4 were investigated in details. Complex 1 shows significant magnetocaloric effect with–ΔSm=20.37 J kg–1 K–1 at 3.0 K and 7 T. Complex 2 exhibits slow relaxation of the magnetization. Complexes 3–6 exhibit both ligand- and metal-centered fluorescent properties. Complex 6 demonstrates fluorescent sensing of DMF and Cu2+ ion.

Microwave-Assisted Synthesis of Solid Epoxy Resins: Study of Molecular Weight by GPC and MALDI-TOF/MS

A new method of preparation of solid epoxy resins (SER) with desired epoxy-group content via an advanced process under microwave irradiation is presented together with the results of molecular weight measurements for narrow oligomeric fractions obtained from chromatographic separation of SER. All the measurements were performed using gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization spectrometry–time of flight mass spectrometry (MALDI-TOF/MS). In the GPC analysis, two types of calibration were used: the first was a standard calibration based on polystyrene standards, while the second was done on the basis of a chromatograms of epoxy resins synthesized from bisphenol A (BPA) and diglycidyl ether of bisphenol A (EDBPA). On the basis of the MALDI-TOF analysis, it was assumed that the purity of starting materials, i.e., low molecular weight epoxy resin, clearly determined the structure of the SER. In order to obtain an SER with linear chain structures and an even number of po...

Two Ag(I)/Cd(II) Coordination Polymers of 2-Fluoroisonicotinic Acid: Syntheses, Structures and Luminescent Properties

Two new coordination polymers, namely [Ag(L)]n (1) and [Cd(L)2(bpe)]n (2) [HL = 2-fluoroisonicotinic acid, bpe = 1,2-bi(4-pyridyl)ethylene], have been synthesized by solvent evaporation and layered-diffusion technique, respectively. The structural analysis revealed that compound 1 is a linear chain structure, whereas compound 2 shows a 1D ladder-like structure with dinuclear [Cd(COO)2] stretched by bpe linkers in parallel arrangement. The thermal stability and photoluminescent properties of both 1 and 2 in the solid state were also investigated, which demonstrated the perfect thermal stability and a certain degree of redshift fluorescent characteristic. Two Ag(I)/Cd(II) CPs were synthesized by solvent evaporation and layered-diffusion technique. Both CPs were characterized by elemental analysis, FT-IR, single-crystal XRD, PXRD and TGA techniques. The solid state photoluminescent study indicates those have strong fluorescent emissions.

Energy level alignment of self-assembled linear chains of benzenediamine on Au(111) from first principles

Using density functional theory (DFT) with a van der Waals density functional, we calculate the adsorption energetics and geometry of benzenediamine (BDA) molecules on Au(111) surfaces. Our results demonstrate that the reported self-assembled linear chain structure of BDA, stabilized via hydrogen bonds between amine groups, is energetically favored over previously studied monomeric phases. Moreover, using a model, which includes nonlocal polarization effects from the substrate and the neighboring molecules and incorporates many-body perturbation theory calculations within the GW approximation, we obtain approximate self-energy corrections to the DFT highest occupied molecular orbital (HOMO) energy associated with BDA adsorbate phases. We find that, independent of coverage, the HOMO energy of the linear chain phase is lower relative to the Fermi energy than that of the monomer phase, and in good agreement with values measured with ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy.

Tunable properties of novel tetra-functional fluorene-based benzoxazines from mixed amines: Synthesis, characterization and curing kinetics

A series of tetra-functional fluorene-based benzoxazines containing both flexible linear aliphatic chain and rigid aromatic structure in their backbones were synthesized using mixed amines such as aniline and n-octylamine, 2,7-dihydroxy-9,9-bis-(4-hydroxyphenyl)fluorene (THPF) and paraformaldehyde as raw materials via Mannich reaction. The prepared benzoxazine monomers were identified by fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H NMR). In addition, the curing behavior, curing kinetics and rheological properties of these monomers as well as the thermal and mechanical properties of their cured resins were studied using a rheometer, differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), and dynamic thermomechanical analyzer (DMA). The newly developed benzoxazines show good processibility, excellent thermal stability and high glass transition temperature (Tg) values ranging from 291 to 307°C. By varying the proportion of n-octylamine to aniline, the properties of these resins are tuned.

Four distinct anionic heterothiometallic W/S/Ag polymeric clusters directed by solvent-coordinated metal cations

The solvent-coordinated metal cations as templates affecting the architectures of anionic heterothiometallic Mo(W)/S/Ag polymeric clusters was investigated. Four W/S/Ag polymeric clusters {[Tb(DMSO)8][W3S12Ag3]}n (1, DMSO=dimethyl sulfoxide), {[Tb(DMF)8][W3S12Ag3]}n (2, DMF=N,N′-dimethylformamide), {[Tb(NMP)8][W4S16Ag5]}n (3, NMP=N-methyl-2-pyrrolidone) and {[Mg(NMP)6][W2S8Ag2]·2NMP}n (4) with distinct 1-D anionic structures were obtained by the reactions of (NH4)2WS4, AgI and M(NO3)x (M=Tb, x=3; M=Mg, x=2) in corresponding solvents (DMSO, DMF or NMP). 1–4 were determined by elemental analysis, IR, UV–Vis, thermogravimetric analysis, X-ray powder and single crystal diffractions. Directed by different solvent-coordinated trivalent terbium metal cations, 1 shows a 1-D anionic helical chain architecture; 2 exhibits a 1-D anionic zigzag chain with hexanuclear [W3S12Ag3]3− repeated units; 3 possesses another kind of 1-D anionic zigzag chain with the unique nonanuclear planar square-like [W4S16Ag5]3− repeated units. While induced by NMP-coordinated bivalent magnesium metal cation, 4 exhibits a 1-D anionic linear chain structure.

Abstract B44: Sulfated fucan inhibits tumor interaction with endothelial cells and tumor growth: Possible contribution of an antivascular endothelial growth factor (VEGF) neutralizing activity

Abstract The primary interaction between tumor and endothelial cells is mediated by endothelial selectins and sialyl-Lewis carbohydrates found on cancer cell surface. Heparin, a sulfated polysaccharide, binds to P- and L-selectins, an effect that has been associated with attenuation of metastasis. However, due to its strong anticoagulant activity, its use in anti-tumor therapy is restricted. Sulfated fucans from sea urchins have simple, unique structures of linear chains of sulfated α-L-fucose in well-defined repetitive patterns. In this study, we tested five sulfated fucans from different species of sea urchins for their ability to interfere with the tumor-endothelium interaction and compared our findings to those obtained with heparin. Our results show that sulfated fucan from L. variegatus (FucSulf I), bearing an unique 2,4-disulfated fucose residue and low anticoagulant activity, inhibits the adhesion of tumor cells to endothelium, tumor transendothelial migration and endothelial cell tubulogenesis, both by inhibiting P-selectin mediated tumor cell adhesion, and VEGF-dependent signaling in endothelial cells. FucSulf I also inhibited proliferation of several types of tumor cell lines in vitro and tumor growth in vivo. Our results indicate this sulfated fucan is a potential antitumor agent and a possible therapeutic alternative to heparin. Citation Format: Viviane Mignone, Camila Castro Figueiredo, Aline Oliveira, Eliene Kozlowski, Lubor Borsig, Mauro Pavão, Paulo Mourão, Veronica Morandi. Sulfated fucan inhibits tumor interaction with endothelial cells and tumor growth: Possible contribution of an antivascular endothelial growth factor (VEGF) neutralizing activity. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr B44.

Influence of Synthetic Methods in the Structure and Dimensionality of Coordination Polymers

Eight different coordination polymers (CPs) of Co2+ and Zn2+ ions with rigid polycarboxylate ligands (fumaric acid (fum) and 2,5-dihydroxyterephalic acid (dhbdc)) have been synthesized using the same solvents, stoichiometry, and counterion but two different synthetic methods: liquid–liquid diffusion method–method A and pH control method–method B. The synthesis using method A resulted in four novel CPs: trans-Co(dmso)2(H2O)2(fum)]n (1), [trans-Zn(dmso)2(H2O)2(fum)]n (2), trans-Co(dmso)2(H2O)2(dhbdc)]n (3), and [trans-Zn(dmso)2(H2O)2(dhbdc)]n (4). Synthesis using method B resulted in one new ([Zn(fum)(OH)2] (6)) and three previously described CPs ([Co3(H2O)4(OH)2(fum)2]·2H2O (5), [Co2(dobdc)] (7), and [Zn2(dobdc)] (8), where dobdc = 2,5-dioxyterephtalic acid). The new CPs (1–4) were also structurally investigated by single-crystal X-ray diffraction techniques, which showed that all of them form one-dimensional (1D) CPs with linear chain structure: it was evidenced that (1) and (3) are isomorphus crystals of (2) and (4), respectively. The crystal structures of 1–4 were compared with similar 1D, two- and three-dimensional (2D and 3D) CPs reported in the literature. Intra- and interchain H-bond networks and coordination (fum, dhbdc, DMSO, water) as well as linkage (fum and dhbdc) isomerism guide the chain configuration (linear or zigzag). It was also demonstrated that the new series of 1D CPs synthesized here (1–4) can work as precursors for CP with higher dimensionality. Our studies showed that the synthetic method plays a crucial role in the crystal growth of coordination polymers.

One-dimensionality in atomic nuclei: A candidate for linear-chainαclustering inC14

The clustering of $\ensuremath{\alpha}$ particles in atomic nuclei results in the self-organization of various geometrical arrangements at the femtometer scale. The one-dimensional alignment of multiple $\ensuremath{\alpha}$ particles is known as linear-chain structure, evidence of which has been highly elusive. We show via resonant elastic and inelastic $\ensuremath{\alpha}$ scattering of a radioactive $^{10}\mathrm{Be}$ beam that excited states in the neutron-rich nucleus $^{14}\mathrm{C}$ agree with recent predictions of linear-chain structure based on an antisymmetrized molecular dynamics model.

Tuning of chain chirality by interchain stacking forces and the structure-property relationship in coordination systems constructed by meridional FeIII cyanide and MnIII Schiff bases.

We synthesized six Fe(iii)-Mn(iii) bimetallic compounds by self-assembling the newly developed mer-Fe cyanide PPh4[Fe(Clqpa)(CN)3]·H2O (1) and PPh4[Fe(Brqpa)(CN)3]·H2O (2) with Mn Schiff base Mn(5-Xsalen)+ cations. These compounds include [Fe(Xqpa)(CN)3][Mn(5-Ysalen)]·pMeOH·qH2O [qpaH2 = N-(quinolin-8-yl)picolinamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = Cl, Y = H (3); X = Cl, Y = Br (4); X = Br, Y = H (5); X = Br, Y = F (6); X = Br, Y = Cl (7); X = Br, Y = Br (8)]. When precursor 1 was used, compounds 3 and 4 were isolated to give a dinuclear entity and a linear chain structure, respectively. The reaction of precursor 2 with the Schiff bases afforded four linear Fe(iii)-Mn(iii) chain complexes. Chain chirality with P- and M-helicity emerges in 4, 7, and 8, while 5 exhibits chain helicity opposite to the previous chain complexes and 6 presents no chain helicity. Such a structural feature is heavily dependent on the interchain π-π contacts and the Fe precursor bridging unit. Chiral induction from a local ethylenediamine link of Y-salen is propagated over the chain via noncovalent π-π interactions. All the bimetallic compounds show antiferromagnetic interactions transmitted by the cyanide linkage. A field-induced metamagnetic transition is involved in 4, 7, and 8, while a field-induced two-step transition is evident in 6. From a magnetostructural viewpoint, the coupling constant is primarily governed by the Mn-Nax-Cax angle (ax = axial) in the bimetallic chain complexes composed of mer-Fe(iii) tricyanides, although the torsion angle plays a role.

Photochemical Reactions of Microcystin-LR Following Irradiation with UV Light

Photochemical reactions of microcystin-LR, a toxic compound produced by some blue green algae, were investigated. Ultraviolet absorption of microcystin-LR was assessed. Time-dependent density functional theory (TDDFT) calculations indicated that absorption peak at 238 nm was mainly due to excitation of electrons from the linear chain structure Adda of microcystin-LR. Irradiation of microcystin-LR with UV light resulted in the reduction of the 238 nm absorption peak and the appearance of a new peak at 300 nm. Density functional theory (DFT) and TDDFT calculations with a model molecule suggested that this 300 nm peak was due to tricyclo-Adda microcystin-LR, an intermediate in photochemical reactions of microcystin-LR. Analysis of the rate of this photochemical reaction showed that it was a first order reaction.