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Chain Structure (chain + structure)
Kinds of Chain Structure Selected AbstractsHydrothermal Synthesis of a New Vanadium Tellurate(VI) with a Novel Chain Structure: (NH4)4{(VO2)2 [Te2O8(OH)2]}×2H2O.CHEMINFORM, Issue 18 2007Hyejin Kim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Effects of Predation Threat on the Structure and Benefits from Vacancy Chains in the Hermit Crab Pagurus bernhardusETHOLOGY, Issue 11 2009Mark Briffa Vacancy chains occur when individuals occupy discrete re-useable resource units, which once abandoned by the current owner can then be occupied by a new owner. In order to enter the newly vacated resource the new owner must first vacate its current resource unit, such that a vacancy chain consists of a series of linked moves between resource units of different value, equivalent to different ,strata' in the chain. Vacancy chains may represent an important route by which resources are distributed through populations. Indeed, the arrival of a new resource has the potential to initiate a series of moves propagating beyond the individual that encounters the new resource unit. Thus, the chain participants as a whole may experience ,aggregate benefits' from the arrival of the new resource unit. The extent of these benefits, however, may not necessarily be evenly distributed between all chain participants; some individuals could receive greater than average benefits by moving through more than one stratum (,skipping') and some individuals could experience a reduction in resource value by moving to a resource unit of lower quality than that occupied initially (a ,backward move'). Such moves represent deviations from the ,ideal' vacancy chains assumed by theory. Here we analyse the aggregate benefits and benefits to individuals participating in vacancy chains of empty gastropod shells in the hermit crab Pagurus bernhardus. We also investigate the effect of predation risk on these two levels of benefits and on chain structure. Adding a new shell at the top of the chain causes an overall increase in shell quality after 24 h but the distribution of benefits between strata in the chain varies with the presence and absence of the predator cue. Although there was significant concordance between chain structure in the presence and absence of the predator cue, the structure was significantly different from an ideal vacancy chain in the absence but not the presence of the predator cue. [source] Syntheses and Characterization of Lead(II) N,N -Bis[1(2)H -tetrazol-5-yl]amine Compounds and Effects on Thermal Decomposition of Ammonium PerchlorateEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2009Weitao Wang Abstract Three new lead(II) N,N -bis[1(2)H -tetrazol-5-yl]amine (H2bta) compounds, [Pb(bta)(H2O)2]n (1), [Pb2(bta)2(bpy)2] (2), and [Pb2(bta)2(phen)2]·2H2O (3), were synthesized. Single-crystal X-ray diffraction reveals that compound 1 has a 1D polymeric zigzag chain structure, whereas compounds 2 and 3 have binuclear structures. In addition, compounds 1,3 were explored as additives to promote the thermal decomposition of ammonium perchlorate by differential scanning calorimetry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Self-Assembly of 1D to 3D Cadmium Complexes: Structural Characterization and PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2005Xing Li Abstract Self-assembly reactions of 5-sulfoisophthalic monosodium salt (NaH2sipa), Cd(NO3)2·4H2O and 2,2'-bipyridine (or 4,4'-bipyridine) under hydrothermal condition give rise to four polymeric complexes, namely {[Cd3(sipa)2(2,2'-bpy)4(H2O)2]·6H2O}n (1), {[Cd(sipa)(H-4,4'-bpy)(H2O)]·2H2O}n (2); {[Cd2(sipa)(4,4'-bpy)3(H2O)3]·[Cd(sipa)(4,4'-bpy)(H2O)]·8H2O}n (3),and {[Cd3(sipa)2(4,4'-bpy)4(H2O)2]·3H2O}n (4), respectively. X-ray diffraction analyses reveal that complex 1 possesses a 1D rail-like chain structure, 2 is a 1D double chain, 3 has a 2D network consisting of an independent [Cd2(sipa)(4,4'-bpy)3(H2O)3]nn+ cationic layer and a [Cd(sipa)(4,4'-bpy)(H2O)]nn, anionic layer, and 4 is a novel 3D self-penetrating network constructed from two mixed bridging ligands. Thermogravimetric analyses (TGA) and fluorescent measurements of complexes 1,4 have also been performed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Mono-, Di- and Polymeric Calcium and Gadolinium Complexes of the Tripodal Ligand 2,2,,2,,-Nitrilotribenzoic AcidEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2005Stefan Wörl Abstract Three novel carboxylate-bridged complexes incorporating the tripodal N,O ligand 2,2,,2,,-nitrilotribenzoic acid H3L of formula [CaII(H2L)(OH2)4][(H2L)]·4H2O (1), [CaII(OH2)4]-[CaII(L)(OH2)2]2·7H2O (2) and [GdIII(L)(OH2)3]2[GdIII(L)-(OH2)4]2·13H2O (3) were synthesized and characterized by X-ray crystallography. In all three complexes, the ligand H3L binds to the metal centre only by its three carboxylate donors, leaving the bridgehead nitrogen atom nonbonding. The calcium(II) ion in the monomeric complex 1 is distorted pentagonal-bipyramidal coordinated, the +1 charge of the complex cation [CaII(H2L)(OH2)4]+ is balanced by an H2L, anion and both units are connected by hydrogen bonds. The polymeric compound 2 displays a one-dimensional chain structure, in which two [CaII(L)]2, units form a dimeric structure and are connected by hydrated CaII ions. 3 contains two different [GdIII(L)(OH2)n] dimers. In one of them the two GdIII ions are linked by two monoatomic carboxylate O-bridges showing a short Gd···Gd distance of 3.99 Å. In the second, a syn - anti carboxylate 1,3-bridge with a longer Gd···Gd distance of 4.96 Å is observed. Magnetic measurements of 3 show paramagnetic behaviour with weak antiferromagnetic coupling. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Sodium Hydro(isothiocyanato)borates: Synthesis and StructuresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2004Heinrich Nöth Abstract Sodium thiocyanate reacts in THF solution with 18-crown-6 to give the molecular compound Na(18-crown-6)(THF)NCS (3) with the N atom of the NCS anion oriented towards Na+. The same reaction with 15-crown-5 yields the ion pair Na(15-crown-5)NCS (4). In contrast, Na(NCS)(py)4, obtained by treating a solution of Na(H3BNCS) in THF with pyridine, yields Na(py)4(NCS) (5), which has a chain structure with hexacoordinate Na atoms coordinated to five N atoms and an S atom. Na(NCS) in THF adds 1 equiv. of BH3 to give Na(H3BNCS)·nTHF. Addition of 18-crown-6 to this solution yields crystals of the salt [Na(18-crown-6)(THF)2][H3BNCS] (1), as shown by X-ray crystallography. Both the cation and the anion show site disorder. However, when 15-crown-5 is used for complexation, the salt [Na(15-crown-5)(THF)][H3BNCS] (2) can be isolated. Its anion shows an almost linear B,N,C,S unit. Only a mixture of (catecholato)(isothiocyanato)borates results on treating Na(NCS) in THF with catecholborane. However, the borate Na[catB(NCS)2] is readily formed by adding Na(NCS) to B -(isothiocyanato)catecholborane. Single crystals of this compound were obtained as the salt [Na(18-crown-6)(THF)2][catB(NCS)2] (6). On the other hand, the reaction of Na(NCS) with 9-borabicyclo[3.3.1]nonane (9-BBN) in THF yields Na[(9-BBN)NCS)]·nTHF, and, on addition of 18-crown-6, the complex [Na(18-crown-6)(THF)2][(9-BBN)NCS] was isolated. Suitable crystals for X-ray structure determination were, however, only obtained by crystallization from tetrahydropyran. This solvate has the rather unusual structure [Na(18-crown-6)(thp)2][{(9-BBN)NCS}2Na(thp)4] (8). The sodiate anion has an Na atom coordinated by two S and four O atoms. DFT calculations support these experimental results: The (isothiocyanato)borates are more stable than the thiocyanato isomers. For the latter a bent structure of the B,S,C,N unit with a B,S,C bond angle of 105.7° is predicted. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Supply chain risk identification using a HAZOP-based approachAICHE JOURNAL, Issue 6 2009Arief Adhitya Abstract Risk management has become imperative for today's complex supply chains. Most approaches reported in the literature have been ad-hoc and specific to certain risks; a general and comprehensive approach is lacking. To address this, we present a structured methodology for risk identification. Supply chain networks are in many ways similar to chemical plants, therefore well-established methods and concepts from chemical process risk management can be adapted to supply chains. Drawing from this analogy, we propose to represent supply chain structure and operations using flow and work-flow diagrams, equivalent to process flow diagrams (PFDs) and operating procedures. Following the HAZard and OPerability (HAZOP) analysis method common in process safety, risk identification can be performed by systematically generating deviations in different supply chain parameters and identifying their possible causes, consequences, safeguards, and mitigating actions. The application and benefits of the proposed approach are demonstrated using a refinery supply chain case study. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Synthesis of soluble poly(para -phenylene) with a long polymer chain: Characteristics of regioregular poly(1,4-phenylene)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2008Itaru Natori Abstract Soluble poly(para -phenylene) having a long polymer chain (more than six repeat units) was synthesized with a tert -butyl end-group (t -PPP) and was found to have improved solubility and excellent optical properties. Poly(1,3-cyclohexadiene) (PCHD) consisting of only 1,4-cyclohexadiene (1,4-CHD) units was synthesized with a tert -butyl end-group (t -PCHD), and completely dehydrogenated to obtain t -PPP. This end-group effectively prevented the crystallization of t -PPP, and polymers containing up to 16 repeat units were soluble in tetrahydrofuran. Soluble t -PPP obtained had an ability to form a tough thin film prepared by spin-coating method. Optical analyses of t -PPP provided strong evidence for a linear polymer chain structure. A block copolymer of t -PPP and a soluble polyphenylene (PPH) was then synthesized, and the excellent optical properties were retained by this block copolymer along with its solubility. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5223,5231, 2008 [source] Large Enhancement in Conductivity of Polyaniline Films by Cold StretchingMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 10 2010Hong-Mei Xiao Abstract The hot-stretching method has been well accepted for enhancing the electrical conductivity of conducting polymer films. High temperature is the prerequisite to soften the polymer to highly align and elongate the polymeric molecular chains. In this study, the cold-stretching method is proposed for the first time to enhance the conductivity of conducting polymeric films. Polyaniline (PANI) films are stretched at room temperature to different strain levels. It is observed that the applied strain has significant effects on the morphology, molecular chain structure, crystallinity, and crosslinking of the PANI films. As a result, the conductivity of PANI films is effectively increased by the cold-stretching process. Particularly, a maximum conductivity with an 18.4-fold increase in the direction parallel to the stretched direction is obtained when the elastic limit strain is applied. Compared to hot stretching, cold stretching is unique due to the extremely low dimensional change and very high efficiency achieved. [source] Synthesis and characterization of semifluorinated polymers and block copolymersMACROMOLECULAR SYMPOSIA, Issue 1 2003Doris Pospiech Abstract The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self-organization. The influence of the chain architecture on the self-organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self-organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains. [source] Development of UHMWPE modified PP/PET blends and their mechanical and abrasive wear behaviorPOLYMER COMPOSITES, Issue 2 2007Navin Chand In this study, polypropylene and polyethylene terephthalate blend were modified by incorporating different percentages of ultrahigh molecular weight polyethylene (UHMWPE) ranging from 1 to 5 phr. Modified blends were prepared by melt mixing the PP/PET blend and UHMWPE. Ultimate tensile strength of UHMWPE filled blend was determined at 10, 20, 50, and 100 mm/min cross head speeds of testing. It was found that increase of cross head speed from 10 to 100 mm/min increases the tensile strength of PP/PET/UHMWPE blends. Maximum ultimate tensile strength is exhibited by the blend containing 2 phr UHMWPE. Breaking strain of the UHMWPE modified and unmodified PP/PET blend increased with the increase of cross head speed due to the highly entangled chain structure of UHMWPE. Shore A hardness of the filled blends also increased from 341 to 356, which is highest for 2 phr UHMWPE. High stress abrasive wear of UHMWPE modified blend was determined by using Suga abrasion tester, model NUS-1 Japan. Wear rate of the PP/PET(90/10) blends having 1, 2, and 5 phr of UHMWPE was determined at different loads such as 1, 3, 5, and 7 N and sliding distances from 6.4 m to 25.6 m. Wear rate values show that UHMWPE has prominent effect on abrasive wear of PP/PET blends. Addition of 2 and 5 phr UHMWPE improved the wear resistance of PP/PET blends at different loads, which has been explained on the basis of improved bonding as compared with pure PP/PET blend and increased hardness. Maximum abrasive wear rate reduction was achieved by adding 2 phr UHMWPE in PP/PET(90/10) blend. POLYM. COMPOS. 28:267,272, 2007. © 2007 Society of Plastics Engineers [source] Optical properties of polyimines: UV,vis and photoluminescence study of undoped and doped polymers in aprotic and protic solventsPOLYMER ENGINEERING & SCIENCE, Issue 8 2007Agnieszka Iwan The optical properties of polyimines (PAs) with structure containing aliphatic,aromatic and aromatic,aromatic moieties are reported. It is demonstrated that the photoluminescence (PL) spectra can be regulated over a wide range by variation in main chain structure and through protonation or intramolecular hydrogen bonding. By combining these two methods it is possible to precisely tune the emission spectra of PAs in the spectral range of 480,531 nm. Luminescent PA/1,3,5-benzenetricarboxamide sulfonic acid complexes were self-organizated from nonamphiphilic ,-conjugated PAs, in DMA and in m -cresol solution. Solvatochromism is manifested in the PL spectra of the undoped and doped PAs. The emission spectra of doped PAs are blue or red shifted relative to the undoped one. Additionally, absorption (UV,vis) properties of the PAs before and after protonation with 1,3,5-benzenetricarboxamide sulfonic acid ("dopant I") were tested. We propose that the novel self-assembly is driven by the amphiphilicity of 1,3,5-benzenetricarboxamide sulfonic acid activated by protonation of PAs. POLYM. ENG. SCI., 47:1179,1186, 2007. © 2007 Society of Plastics Engineers [source] Modification of the thermal properties and crystallization behaviour of poly(ethylene terephthalate) by copolymerizationPOLYMER INTERNATIONAL, Issue 3 2003Darwin P, R Kint Abstract Poly(ethylene terephthalate) (PET) is a widely used polyester, which can be crystallized from the melt over a wide range of supercooling conditions or, alternatively, quenched into the amorphous state and, subsequently, crystallized by thermal treatment above the glass-transition temperature. It is well known that the crystallization of PET can be hindered by means of copolymerization or reactive blending. The incorporation of comonomeric units into the polymer backbone leads to an irregular chain structure and thereby inhibits regular chain packing for crystallization. The crystallization of PET copolyesters is strongly influenced by the chain microstructure regarding comonomer distribution, randomness and length of the crystallizable ethylene terephthalate sequences. This paper is mainly devoted to the thermally induced crystallization behaviour of PET and to reviewing the efforts that have been made in the last decade to modify the glass-transition and melting temperatures, the crystallinity and the crystallization rate of this polyester. Furthermore, some illustrative experimental data obtained from isothermal and non-isothermal crystallization of PET are included in this study. © 2003 Society of Chemical Industry [source] Sonochemical synthetic methods to produce functionalized conducting copolymersPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2010P. Najafi Moghadam Abstract Polyaniline (PANI) is one of the most investigated intrinsically conducting polymers. Copolymerization of aniline with aniline derivatives was considered one of the most effective and promising ways of improving the properties of PANI. In this work, firstly ethyl 3-aminobenzoate and butyl 3-aminobenzoate were synthesized from 3-aminobenzoic acid by direct esterification. Then the copolymerization of 3-amino benzoic acid, ethyl 3-aminobenzoate, and butyl 3-aminobenzoate with aniline was carried out by sonochemical polymerization in aqueous hydrochloric acid using ammonium persulfate (APS) as an initiator. The effects of variation in the molar ratio of the two monomers on chain structure, conductivity, and the redox properties of the copolymer are discussed. The prepared polymers are characterized by 1H NMR spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Thermal behavior of the prepared copolymers was studied by differential scanning calorimetry. The copolymers were doped with HCl and their conductivity was measured. Copyright © 2009 John Wiley & Sons, Ltd. [source] Thermal conductive PS/graphite compositesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2009Haoming Tu Abstract Polystyrene (PS) was compounded with graphite that possesses high thermal conductivity and layer structures, and the PS/graphite thermal conductive nano-composites were prepared. Thermal conductivity of PS improved remarkably in the presence of the graphite, and a much higher thermal conductivity of 1.95,W/m,K can be achieved for the composite with 34,vol% of colloidal graphite. The Maxwell-Eucken model and the Agari model were used to evaluate the thermal conductivity of the composites. For the purpose of improving the interfacial compatibility of PS/graphite, realizing the exfoliation and nano-dispersion of graphite in the PS matrix, three intercalation methods, including rolling intercalation, solvent intercalation, and pan milling intercalation, were applied to prepare the composites, and the morphologies, thermal conductivities, and mechanical properties of the composites were investigated. It should be noted that the one prepared by pan milling intercalation not only had excellent thermal conductivity but also much higher mechanical properties, resulting from a high degree of layer exfoliation of the graphite, the formation of the chain structure agglomerates of the graphite, and the creation of more conductive paths under the strong shear stress of pan milling. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new chain structure: catena -poly[4,4,-(ethane-1,2-diyl)dipyridinium bis[[aquadifluoridooxidovanadate]-,-fluorido]]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010David W. Aldous The title compound, {(C12H12N2)[V2F6O2(H2O)2]}n, features a novel extended-chain moiety, [VOF2F2/2(H2O)]n, comprising trans vertex-connected VOF4(H2O) octahedra. The octahedra themselves show the characteristic distortion due to the off-centring of the V4+ ion, such that a short terminal V=O bond and an elongated trans V,OH2 bond are present. Hydrogen bonding from the water molecules to terminal F atoms in adjacent chains generates associated chain dimers, which are loosely linked into sheets via additional hydrogen bonding involving the organic moieties. Structural relationships with previously described vanadium oxyfluoride species are briefly discussed. [source] catena -Poly[bis(trimethylphenylammonium) [hexa-,-chlorido-dichloridotricuprate(II)]]: an alternating zigzag chain of CuCl4 and Cu2Cl6 complexesACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Marcus R. Bond The title compound, {(C9H14N)2[Cu3Cl8]}n, consists of parallel chains of alternating quasiplanar Cu2Cl6 and planar CuCl4 complexes separated by trimethylphenylammonium cations. Both inorganic complexes possess inversion symmetry. Pairs of neighboring chloride ions of the CuCl4 complex each form a symmetric bridge and an asymmetric bridge to Cu2Cl6 complexes on either side. The Cu2Cl6 complex contains two symmetric chloride bridges between the copper cations with a terminal chloride bound to each five-coordinated CuII ion. The CuCl4 complex completes its coordination environment by forming two long semicoordinate contacts to the bridging chloride ions of neighboring Cu2Cl6 complexes. The use of the bridging rather than the terminal chloride ions to form semicoordinate contacts generates a new zigzag chain structure that differs from the straight chain structures found for other A2Cu3Cl8 compounds. The zigzag chain structure is adopted so as to conform to the shorter repeat distance dictated by stacking of the organic cations. [source] Proton transfer versus nontransfer in compounds of the diazo-dye precursor 4-(phenyldiazenyl)aniline (aniline yellow) with strong organic acids: the 5-sulfosalicylate and the dichroic benzenesulfonate salts, and the 1:2 adduct with 3,5-dinitrobenzoic acidACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Graham Smith The structures of two 1:1 proton-transfer red,black dye compounds formed by reaction of aniline yellow [4-(phenyldiazenyl)aniline] with 5-sulfosalicylic acid and benzenesulfonic acid, and a 1:2 nontransfer adduct compound with 3,5-dinitrobenzoic acid have been determined at either 130 or 200,K. The compounds are 2-(4-aminophenyl)-1-phenylhydrazin-1-ium 3-carboxy-4-hydroxybenzenesulfonate methanol solvate, C12H12N3+·C7H5O6S,·CH3OH, (I), 2-(4-aminophenyl)-1-phenylhydrazin-1-ium 4-(phenyldiazenyl)anilinium bis(benzenesulfonate), 2C12H12N3+·2C6H5O3S,, (II), and 4-(phenyldiazenyl)aniline,3,5-dinitrobenzoic acid (1/2), C12H11N3·2C7H4N2O6, (III). In compound (I), the diazenyl rather than the aniline group of aniline yellow is protonated, and this group subsequently takes part in a primary hydrogen-bonding interaction with a sulfonate O-atom acceptor, producing overall a three-dimensional framework structure. A feature of the hydrogen bonding in (I) is a peripheral edge-on cation,anion association also involving aromatic C,H...O hydrogen bonds, giving a conjoint R12(6)R12(7)R21(4) motif. In the dichroic crystals of (II), one of the two aniline yellow species in the asymmetric unit is diazenyl-group protonated, while in the other the aniline group is protonated. Both of these groups form hydrogen bonds with sulfonate O-atom acceptors and these, together with other associations, give a one-dimensional chain structure. In compound (III), rather than proton transfer, there is preferential formation of a classic R22(8) cyclic head-to-head hydrogen-bonded carboxylic acid homodimer between the two 3,5-dinitrobenzoic acid molecules, which, in association with the aniline yellow molecule that is disordered across a crystallographic inversion centre, results in an overall two-dimensional ribbon structure. This work has shown the correlation between structure and observed colour in crystalline aniline yellow compounds, illustrated graphically in the dichroic benzenesulfonate compound. [source] A cyanide-bridged FeII,NdIII bimetallic assembly with a one-dimensional ladder-like chain structureACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Yan Xu The title complex, catena -poly[[[(2,2,-bipyridine-1,2N,N,)tris(methanol-2,O)(nitrato-2,2O,O,)-,-cyanido-1:2C:N -cyanido-1,C -iron(II)neodymium(III)]-di-,-cyanido-1:2,C:N;2:1,N:C] methanol solvate], {[FeIINdIII(CN)4(NO3)(C10H8N2)(CH3OH)3]·CH3OH}n, is made up of ladder-like one-dimensional chains oriented along the c axis. Each ladder consists of two strands based on alternating FeII and NdIII centers connected by cyanide bridges. Furthermore, two such parallel chains are connected by additional cyanide cross-pieces (the `rungs' of the ladder), which likewise connect FeII and NdIII centers, such that each [Fe(CN)4(bipy)]2, unit (bipy is 2,2,-bipyridine) coordinates with three NdIII centers and each NdIII center connects with three different [Fe(CN)4(bipy)]2, units. In the complex, the iron(II) cation is six-coordinated with a distorted octahedral geometry and the neodymium(III) cation is eight-coordinated with a distorted dodecahedral environment. [source] Poly[[di-,-aqua-tetraaquadi-,-hydroxido-bis(,3 -3-nitrophthalato)tricopper(II)] dihydrate]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Feng-Qin Wang The novel title complex, {[Cu3(C8H3NO6)2(OH)2(H2O)6]·2H2O}n, has a one-dimensional polymeric double chain structure where the three Cu atoms are linked by ,2 -OH and ,2 -H2O groups, and these trinuclear centres are bridged by two 3-nitrophthalate ligands. The asymmetric unit contains one and a half crystallographically independent Cu atoms (one lying on a centre of inversion), both coordinated by six O atoms and exhibiting distorted octahedral coordination geometries, but with different coordination environments. Each 3-nitrophthalate ligand connects to three Cu atoms through two O atoms of one carboxylate group and one O atom of the nitro group. The remaining carboxylate group is free and is involved in intrachain hydrogen bonds, reinforcing the chain linkage. [source] catena -Poly[[[aqua[3-(2-pyridylsulfanyl)propionato N -oxide-,O1]copper(II)]-,-[3-(2-pyridylsulfanyl)propionato N -oxide-,3O3:O1,O1,] dihydrate]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2008Murugan Indrani In the title complex, {[Cu(C8H8NO3S)2(H2O)]·2H2O}n, the CuII cation has a distorted square-pyramidal coordination environment consisting of five O atoms, one from a water molecule, one from an N,O group and the other three from the carboxylate groups of two 3-(2-pyridylsulfanyl)propionate N -oxide anions. The aqua[3-(2-pyridylsulfanyl)propionato N -oxide]copper(II) moieties are bridged by 3-(2-pyridylsulfanyl)propionate N -oxide anions to form an infinite three-dimensional coordination polymer with a zigzag chain structure. The crystal structure is stabilized by hydrogen bonds. [source] A one-dimensional nickel(II) coordination polymer containing 2,6-dipicolinate and dipyrido[3,2- a:2,,3,- c]phenazineACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2007Yi Ma A new coordination polymer, catena -poly[[(dipyrido[3,2- a:2,,3,- c]phenazine-,2N,N,)nickel(II)]-,-2,6-dipicolinato-,4O2,N,O6:O2,], [Ni(C7H3NO4)(C18H10N4)]n, exhibits a one-dimensional structure in which 2,6-dipicolinate acts as a bridging ligand interconnecting adjacent nickel(II) centers to form a chain structure. The asymmetric unit contains one NiII center, one dipyrido[3,2- a:2,,3,- c]phenazine ligand and one 2,6-dipicolinate ligand. Each NiII center is six-coordinated and surrounded by three N atoms and three O atoms from one dipyrido[3,2- a:2,,3,- c]phenazine ligand and two different 2,6-dipicolinate ligands, leading to a distorted octahedral geometry. Adjacent chains are linked by ,,, stacking interactions and weak interactions to form a three-dimensional supramolecular network. [source] Hydrogen-bonded supramolecule of N,N,-bis(4-pyridylmethyl)oxalamide and a zigzag chain structure of catena -poly[[[dichloridocobalt(II)]-,- N,N,-bis(4-pyridylmethyl)oxalamide-,2N4:N4,] hemihydrate]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2007Gene-Hsiang Lee N,N,-Bis(4-pyridylmethyl)oxalamide, C14H14N4O2, exists as a dimer which is extended into a two-dimensional network with other dimers through pyridine,amide hydrogen bonds. The crystal structure of the title coordination polymer, {[CoCl2(C14H14N4O2)]·0.5H2O}n, features a one-dimensional zigzag chain, in which the cobalt ion sits at a twofold symmetry position and adopts a tetrahedral geometry, and the bridging ligand lies on an inversion center and connects to CoII ions in a bis-monodentate mode. Furthermore, two interwoven chains create a cavity of ca 8.6 × 8.6,Å, which produces a three-dimensional channel. Water molecules are held in the channel by hydrogen bonds. [source] Crystallographic report: Bis(isonicotinonitrile)cadmium diselencyanate, [Cd(SeCN)2(pyCN)2] (pyCN = isonicotinonitrile)APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2003Dacheng Li Abstract The title compound, [Cd(SeCN)2(pyCN)2],, adopts an extended one-dimensional chain structure in which the neighboring cadmium atoms are bridged by two selenocyanate ions. The central cadmium atom has a distorted octahedral geometry defined by two isonicotinonitrile and four selenocyanate ions in a 4N2Se fashion. Copyright © 2003 John Wiley & Sons, Ltd. [source] A simple Markov chain structure for the evolution of credit ratingsAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 6 2007Amparo Baíllo Abstract We focus on continuous Markov chains as a model to describe the evolution of credit ratings. In this work it is checked whether a simple, tridiagonal type of generator provides a good approximation to a general one. Three different tridiagonal approximations are proposed and their performance is checked against two generators, corresponding to a volatile and a stable period, respectively. Copyright © 2007 John Wiley & Sons, Ltd. [source] Unexpected Structural Diversity in Alkali Metal Azide-Crown Ether Complexes: Syntheses, X-ray Structures, and Quantum-Chemical CalculationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2006Michael D. Brown Abstract A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N3)], [Na([15]crown-5)(N3)], [Na([15]crown-5)(H2O)2]N3, [K([18]crown-6)(N3)(H2O)], [Rb([18]crown-6)(N3)(H2O)], [Cs([18]crown-6)(N3)]2, and [Cs([18]crown-6)(N3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the MNterminal metal,azide bond length and charge densities on the metal (M) and terminal nitrogen centre (Nterminal) in these complexes has allowed the nature of the metal,azide bond to be probed in each case. The bonding in these complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre and minimising ligand-ligand repulsions. The structures of the crown ether complexes determined in this work show the subtle interplay of such factors. The significant role of hydrogen bonding is also demonstrated, most clearly in the structures of the K and Rb dimers, but also in the chain structure of the hydrated Cs complex. [source] Crystal structure, thermal analysis and theoretical calculation of a one-dimensional chain complex [zn(dafo)2(H2O)2](NO3)2CHINESE JOURNAL OF CHEMISTRY, Issue 8 2004Rong-Lan Zhang Abstract A novel one-dimensional chain complex [Zn(dafo)2(H2O)2](NO3)2 was obtained when we tried synthesizing a mixed ligand supramolecular compound of Zinc(II) with dafo and o -phthalic acid. Its structure was determined by single-crystal X-ray diffraction analysis. The crystal belongs to triclinic system, P -1 space group. The crystallographic data: a=0.6989(4) nm, b=0.8281(5) nm, c=1.0231(5) nm, ,=94.934(5)°, ,=91.366(7)°, ,=99.820(7)°, V=0.5809(5) nm3, Z= 1, F(000)=300, Mr=589.78, Dc=1.686 g/cm3, ,(Mo K,)=1.130 mm,1, R1=0.0521, wR2=0.1096. The analysis of the crystal structure indicates that the compound has a one-dimensional chain structure which is formed by hydrogen bonds. The constitutes of the title complex were proved by elemental analysis, IR spectra and thermal analysis. On the basis of the experimentation, the complex was calculated by DFT-B3LW/LANL2DZ in Gaussian-98w also. [source] Synthesis, structure and photoluminescence of two zinc carboxylate polymers with different coordination architecturesCHINESE JOURNAL OF CHEMISTRY, Issue 10 2003Hong Ding Abstract The hydrothermal reaction of ZnO with benzene-1,4-dicarboxylic add gave Zn·BDC·2H2O (1) and Zn-BDC·H2O (2) (BDC = benzene-1, 4-dicarboxylate), respectively. Polymer 1 (C4H4O3ZH0.5) shows a one-dimensional zigzag chain structure built up from the alternate connection of tetrahedral ZnO4 and BDC units. Polymer 2 (C4H3O2.5Zn0.5) possesses a three-dimensional framework containing infinite zigzag Zn·Zn·Zn pseudochains generated by five-coordinate zinc centers and a rectangular channel system including three groups of different straight channels along the [001], [010] and [60,1] directions. The two metal-organic polymeric compounds exhibit strong photoluminescent emission bands at 402 nm (,ex = 260 nm) (for 1) and at 344 nm and 385 nm (,ex = 279 nm) (for 2) in the solid state at room temperature. [source] The Impact of E-Replenishment Strategy on Make-to-Order Supply Chain PerformanceDECISION SCIENCES, Issue 1 2005E. Powell Robinson Jr. ABSTRACT This research investigates the impact of electronic replenishment strategy on the operational activities and performance of a two-stage make-to-order supply chain. We develop simulation-based rolling schedule procedures that link the replenishment processes of the channel members and apply them in an experimental analysis to study manual, semi-automated, and fully automated e-replenishment strategies in decentralized and coordinated decision-making supply chain structures. The average operational cost reductions for moving from a manual-based system to a fully automated system are 19.6, 29.5, and 12.5%, respectively, for traditional decentralized, decentralized with information sharing, and coordinated supply chain structures. The savings are neither equally distributed among participants, nor consistent across supply chain structures. As expected, for the fully coordinated system, total costs monotonically decrease with higher levels of automation. However, for the two decentralized structures, under which most firms operate today, counter-intuitive findings reveal that the unilateral application of e-procurement technology by the buyer may lower his purchasing costs, but increase the seller's and system's costs. The exact nature of the relationship is determined by the channel's operational flexibility. Broader results indicate that while the potential economic benefit of e-replenishment in a decentralized system is substantial, greater operational improvements maybe possible through supply chain coordination. [source] Hierarchical Structures in Tin(II) OxalatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2008Padmini Ramaswamy Abstract Six new SnII oxalates exhibiting a hierarchy of structures have been prepared employing hydrothermal methods. The compounds I [C10N2H10][Sn(C2O4)2], II [C10N2H10][Sn2(C2O4)3], and III [C8N4H26][Sn(C2O4)2]2·2H2O possess zero-dimensional molecular structures; IV [C10N2H8]2[Sn(C2O4)]2 and V [C12N2H8][SnC2O4] have one-dimensional chain structures; and compound VI [C5N2H14]2[Sn4(C2O4)6]·7H2O has a two-dimensional layer structure. The SnII ions have 4- and 6-coordination with square-pyramidal or pentagonal-bipyramidal geometry, in which the lone pair of electrons also occupies one of the vertices. Weak intermolecular forces such as hydrogen-bond interactions, ,···, interactions, and lone-pair,, interactions have been observed and appear to lendstructural stability. Theoretical studies indicate that the ,···, interaction energy between the bound 1,10-phenanthroline molecules is of the order of 5,6 kcal,mol,1 in V. Natural bond orbital (NBO) analysis on two model compounds, II and IV, indicates reasonable lone-pair,, interactions. The close structural relationship between all the compounds indicates that a building-up process from the zero-dimensional monomer can be considered. The present structures provide opportunities for evaluating the structure-directing role of the lone pair of electrons of SnII.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] | ||||||||||||||||