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Polymeric Structure (polymeric + structure)
Selected AbstractsSynthesis of a Single Four-Ring (S4R) Molecular Zinc Phosphate and Its Assembly to an Extended Polymeric Structure: A Single-Crystal and in situ MAS NMR Investigation.CHEMINFORM, Issue 51 2003Srinivasan Natarajan Abstract For Abstract see ChemInform Abstract in Full Text. [source] Molecular Iodine Stabilization in an Extended N···I,I···N AssemblyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009Francesco Isaia Abstract The adduct [bis(quinoxaline)-2,2,,3,3,-disulfide·I2], (Q2S2·I2), (1) can be easily synthesised from the reaction of Q2S2 and I2 in CH2Cl2 or, in the absence of any solvent, through diffusion of I2 vapours at 60 °C. X-ray diffraction analysis shows the presence of an extended N···I,I···N assembly in which each I2 molecule links a Q2S2 molecule at both ends through a nitrogen atom to form a polymeric species; the d(I,I) and d(N,I) bond lengths confirm a very weak nitrogen,iodine interaction at the base of the N···I,I···N assembly. DFT calculations provide optimised distances for the N···I and I,I bonds and explanation for the zigzag chain formation: the mPW1PW functional and the B3LYP hybrid functional with a variety of basis sets for the I atomic species [CRENBL, LANL2DZ, LANL2DZ(d,p), LANL08(d), SBKJC, SBKJC polarised-LFK and Stuttgart RLC] have been tested. Compound 1 proved stable up to nearly 100 °C, and the stability is to be mainly attributed to the lattice energy of its polymeric structure then to donor,acceptor stabilisation. The facile insertion of molecular iodine into the Q2S2 network makes this compound an interesting iodine sponge, suitable for I2 storage; moreover, Q2S2 can easily collect and release I2(g) by a temperature-controlled process (60 and 97 °C, respectively). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Unusual T4(1) Water Chain Stabilized in the One-Dimensional Chains of a Copper(II) Coordination PolymerEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Yi Jin Abstract A novel T4(1) water chain in a new CuII coordination polymer, {[Cu(C4H6N2)2(C4H2O4)] (H2O)3}n (1, where C4H6N2 = 2-methylimidazole, C4H2O4 = maleate), has been synthesized and structurally characterized by single-crystal X-ray diffraction. Thermogravimetry, infrared spectroscopy, elemental analysis, and magnetic analysis have also been used to characterize 1. Complex 1 crystallizes in the trigonal space group P3221, and the 1-D chains composed of cyclic water tetramers play an important role in stabilizing the overall polymeric structure. Furthermore, this 1-D water chain presents an unusual association mode of water molecules.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Preparation and Structure of Oligomeric Iodosylbenzene Sulfate (PhIO)3·SO3: Stable and Water-Soluble Analog of IodosylbenzeneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2007Alexey Y. Koposov Abstract New phenyliodine(III) sulfate (PhIO)3·SO3, which has a complex polymeric structure of the trimeric iodosylbenzene units linked by sulfate anions, can be conveniently prepared by treatment of (diacetoxy)iodobenzene with sodium bisulfate in the presence of water. This sulfate can find practical application as a readily available, stable, and water-soluble hypervalent iodine reagent with a reactivity pattern similar tothat of iodosylbenzene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Aerobic, Chemoselective Oxidation of Alcohols to Carbonyl Compounds Catalyzed by a DABCO-Copper Complex under Mild ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2007Sreedevi Mannam Abstract A DABCO-copper(I) chloride complex (5 mol,%) together with TEMPO (5 mol,%) in nitromethane as solvent has been used as an efficient catalytic system for the selective oxidation of benzylic and allylic alcohols into the corresponding carbonyl compounds at room temperature where molecular oxygen acts as an ultimate, stoichiometric oxidant and water is the only by-product. The solid-state structure determination of the DABCO-copper complex shows that the copper is in the +II oxidation state with trigonal bipyramidal geometry and exists in a linear polymeric structure due to strong hydrogen bonding. [source] Indication of Local Phase Separation in Polyimide/Silica Hybrid Polymers,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Antonino Bartolotta Abstract PI/SiO2 hybrid polymers involving the in situ generation of SiO2 particles through the sol/gel route have emerged as promising materials in many fields of modern technology thanks to their unique structural characteristics. In this paper their structural and dynamic properties were investigated by FT-IR and DMTA as a function of SiO2 content. All data consistently highlight a loosening of polymeric structure due to the presence of SiO2 nanoparticles and suggest a silica-induced structural change most probably due to a sub-micrometer scale SiO2 phase separation. Our results demonstrate how the analysis of sub-glass ,-relaxation dynamics can be exploited to investigate sub-micro phase segregation in such materials. [source] Polymorphs of DABCO monohydrate as structural analogues of NaClACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Barbara Wicher A new crystalline form of 1,4-diazabicyclo[2.2.2]octane (DABCO) monohydrate, C6H12N2·H2O, crystallizing in the space group P31, has been identified during screening for cocrystals. There are three DABCO and three water molecules in the asymmetric unit, with two DABCO molecules exhibiting disorder over two positions related by rotation around the N...N axis. As in the monoclinic C2/c (Z, = 2) polymorph, the molecular components are connected via O,H...N hydrogen bonds into a polymeric structure that consists of linear O,H...N(CH2CH2)3N...H,O segments, which are approximately mutually perpendicular. The two polymorphic forms of DABCO monohydrate can be considered as structural analogues of NaCl, with the nearly globular DABCO molecules showing distorted cubic closest packing and all octahedral interstices occupied by water molecules. [source] Poly[bis(,3 -5,-carboxy-2,2,-bipyridine-5-carboxylato-,4O:N,N,:O,)lead(II)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Cheng-Zhi Xie The title compound, [Pb(C12H7N2O4)2]n, obtained by reaction of Pb(NO3)2 and 2,2,-bipyridine-5,5,-dicarboxylic acid (H2bptc) under hydrothermal conditions, has a structure in which the unique PbII cation sits on a twofold axis and is octa-coordinated by four O-atom donors from four Hbptc, ligands and four N-atom donors from two Hbptc, ligands in a distorted dodecahedral geometry. With each PbII cation connected to six Hbptc, ligands and each Hbptc, ligand bridging three PbII cations, a three-dimensional polymeric structure is formed. From a topological point of view, the three-dimensional net is binodal, with six-connected (the PbII cation) and three-connected (the Hbptc, ligand) nodes, resulting in a distorted rutile (42.8)2(4489122) topology. [source] Lagoden dimethylformamide hemisolvate dihydrate: absolute configuration, dipolar interactions and hydrogen-bonding interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Barbara Wicher Lagoden (L·3H2O, where L is Na+·C20H33O6,; sodium 3,,16,18-trihydroxy-8,13- epi -9,13-epoxylabdan-15-oate trihydrate) is widely used as an effective haemostatic agent. It has been crystallized from dimethylformamide (DMF) as sodium 3,,16,18-trihydroxy-8,13- epi -9,13-epoxylabdan-15-oate dimethylformamide hemisolvate dihydrate, Na+·C20H33O6,·0.5C3H7NO·2H2O or L2·DMF·4H2O, and the asymmetric unit contains two of the latter formulation. The four symmetry-independent Na+ cations and lagoden anions, one DMF molecule and six of the eight symmetry-independent water molecules assemble into a one-dimensional polymeric structure via dipolar and hydrogen-bonding interactions. The lagoden anions coordinate to the Na+ cations via the carboxylate groups and the two primary hydroxy groups, whereas the secondary OH groups are solely involved in hydrogen bonding. Two of the four symmetry-independent lagoden anions act in a chelating mode, forming seven-membered chelate rings. The absolute structure, based on anomalous dispersion data collected at 130,K with Cu K, radiation, confirms an inverted configuration at chiral centres C8 and C13 (labdane numbering) relative to the labdane skeleton. [source] Mn3(OAc)6·CH3CN: a porous dehydrated manganese(II) acetateACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2009John Fielden The crystal structure of a new form of dehydrated manganese(II) acetate, poly[[hexa-,3 -acetato-trimanganese(II)] acetonitrile solvate], {[Mn3(CH3COO)6]·CH3CN}n, (I), reveals a three-dimensional polymeric structure based on an {Mn3} trimer. The {Mn3} asymmetric unit contains three crystallographically independent Mn positions, comprising a seven-coordinate center sharing a mirror plane with a six-coordinate center, and another six-coordinate atom located on an inversion center. Two of the four crystallographically independent acetate (OAc) ligands, as well as the acetonitrile solvent molecule, are also located on the mirror plane. The Mn atoms are connected by a mixture of Mn,O,Mn and Mn,OCO,Mn bridging modes, giving rise to face- and corner-sharing interactions between manganese polyhedra within the trimers, and edge- and corner-sharing connections between the trimers. The network contains substantial pores which are tightly filled by crystallographically located acetonitrile molecules. This structure represents the first porous structurally characterized phase of anhydrous manganese(II) acetate and as such it is compared with the closely related densely packed anhydrous manganese(II) acetate phase, solvent-free ,-Mn(OAc)2. [source] Powder study of poly[(,2 -2,2-dimethylpropane-1,3-diyl diisocyanide)-,2 -iodido-silver(I)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009Mwaffak Rukiah In order to explore the chemistry of the bidentate ligand 2,2-dimethylpropane-1,3-diyl diisocyanide and to investigate the effect of counter-ions on the polymeric structure of (2,2-dimethylpropane-1,3-diyl diisocyanide)silver(I) complexes, the title polymeric compound, [AgI(C7H10N2)]n, was synthesized by treatment of 2,2-dimethylpropane-1,3-diyl diisocyanide with AgI. X-ray powder diffraction studies show, as expected, a polymeric structure, similar to the very recently reported Cl, and NO3, analogues [AgX(C7H10N2)]n (X = Cl, or NO3,). In the title structure, the AgI centre is bridged to two adjacent AgI neighbours by bidentate 2,2-dimethylpropane-1,3-diyl diisocyanide ligands via the NC groups to form [Ag{CNCH2C(CH3)2CH2NC}]n chains. The iodide counter-ions crosslink the AgI centres of the chains to form a two-dimensional polymeric {[Ag{CNCH2C(CH3)2CH2NC}]I}n network. This study also shows that this bidentate ligand forms similar polymeric structures on treatment with AgX, regardless of the nature of the counter-ion X,, and also has a strong tendency to form polymeric complexes rather than dimeric or trimeric ones. [source] Crystallographic report: [Diaqua bis(2,2,-bipyridine)(µ-naphthalene-1,4,5,8-tetracarboxylato)]dizinc(II) tetrahydrateAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2004Xiao-Jun Zhao Abstract The title complex features a two-dimensional polymeric structure owing to the presence of µ4 -bridging naphthalene-1,4,5,8-tetracarboxylate ligands. The trigonal bipyramidal coordination geometry for zinc is completed by a chelating 2,2,-bipyridine and a water molecule. Copyright © 2004 John Wiley & Sons, Ltd. [source] 1-Phenyl-5-(piperidinomethyl)-1H -tetrazoleACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004Alexander S. Lyakhov In the molecule of the title 1,5-disubstituted tetrazole, C13H17N5, the tetrazole and benzene rings are not coplanar, having a dihedral angle of 42.96,(5)° between them. The piperidine fragment adopts a chair conformation, and there is a non-classical intramolecular contact between the benzene H atom and the piperidine N atom. Intermolecular C,H,, interactions involving the piperidine C,H groups and the benzene rings are responsible for the formation of two-dimensional networks, extending parallel to the ab plane. These networks are linked together into a three-dimensional polymeric structure via,,, stacking interactions between the tetrazole rings of two adjacent molecules. [source] Pulsatile Ventricular Assist Device with Pericardial Inner LiningARTIFICIAL ORGANS, Issue 11 2001Adolfo A. Leirner Abstract: Preserved pericardium in contact with blood is not thrombogenic, therefore avoiding the use of anticoagulants, and has excellent mechanical properties. Our objective is to take advantage of these characteristics and build a pulsatile ventricular assist device (VAD) with pericardium used as the inner lining of the blood chamber. A mold is used for the tanning of the pericardium, rendering it with an exact shape. A flexible polymeric structure is designed to serve as a base for the pericardium, guiding it and limiting its rate of strain. It consists of two halves, which when outfitted with the interior pericardium lining and connected to each other, form the blood chamber. This assembly is housed in rigid polyvinyl chloride (PVC) shells making up the air chamber for the pneumatic activation. Valves are likewise made of pericardium. Sealing of the chambers was tested statically up to 300 mm Hg with no air or fluid leakage. The device was tested for 60 continuous days in a mock loop, demonstrating hydrodynamic performance adequate for ventricular assist. Micrographs (confocal laser and scanning electron microscopy) were obtained of several pericardium areas, especially on the flexing regions that are a transition between the wet and dry regions. No sign of damage to the pericardium was observed either with the naked eye or at the microscopic level. From the hydraulic performance and materials viewpoints, a completely pericardium-lined pulsatile VAD displaying a polymeric structure that avoids unpredictable bending and limits strain is feasible. The results warrant further studies regarding biocompatibility and strength advantages. [source] Studies in Solution and the Solid State of Coordination Compounds Derived from LiBH4, NaBH4, and Bidentate Aromatic AminesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2010Milagros Aguilar-Martínez Abstract The mixture of 2,2,-bipyridylamine, 2,2,-bipyridine, 1,10-phenanthroline, 1,2-phenylendiamine, and 1,4-phenylendiamine each with LiBH4 and NaBH4 in a 1:1 molar ratio in THF yields seven new complexes of the type MBH4·L-THF and one complex of the type MBH4·L. These compounds were characterized by IR and NMR spectroscopy and X-ray single-crystal structure determinations. In the solid state, the [BH4], group is bidentate, as deduced from the stretching patterns observed in IR spectra and confirmed by X-ray single-crystal structure analysis. NMR spectroscopy showed that all amines act as bidentate ligands and are symmetrically coordinated to the metal cation. Complexes LiBH4 -2,2,-bipyridine-THF (1), NaBH4 -2,2,-bipyridine-THF (2), LiBH4 -1,10-phenanthroline-THF (3), and NaBH4 -1,10-phenanthroline-THF (4) have a discrete molecular structure, whereas the complexes LiBH4 -1,2-phenylendiamine-THF (5), NaBH4 -1,2-phenylendiamine-THF (6), LiBH4 -2,2,-dipyridilamine (7), and LiBH4 -1,4-phenylendiamine-THF (8) have polymeric structures in the solid state. N -borane-dipyridylamine adduct 9 was isolated from an aged solution of 7. IR spectroscopy of the new complexes showed that the structures of complexes 1, 3, 4, and 6 are maintained in the solid state and in solution. A rotational barrier for the [BH4], group of less than 38 KJ,mol,1 was estimated for some of the new complexes. [source] Smart polymeric coatings,recent advancesADVANCES IN POLYMER TECHNOLOGY, Issue 1 2007W. Feng Abstract There is an ever-growing number of developments that aim to bring novel functionalities to polymer-coating systems with nanotechnology being one of them. This article will cover recent advances in the field of smart polymeric structures that are used in protective coatings in terms of stimulus and response, sensing mechanisms, and current or potential applications. Such structures are commonly based on polymers modified through organic or inorganic additives. Emphasis is placed on smart sensors used for detecting the onset of corrosion on polymer coated ferrous and nonferrous substrates. Examples of self-healing and repair through the action of microcapsules are also presented. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:1,13, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20083 [source] Development of a liquid extraction method and comparison with dynamic thermal stripping,thermal desorption (DTS,TD) method: sorption of D -limonene by flexible packaging filmsPACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2004Cengiz Caner Abstract The sorption of D -limonene into polymeric structures in contact with food simulant liquids (ethanol and acetic acid solutions) was determined using two methods, liquid extraction (LE) and dynamic thermal stripping,thermal desorption (DTS,TD). The polymeric films studied were PP (polypropylene), PE/nylon/EVOH/PE (polyethylene/nylon/ethylene vinyl alcohol/polyethylene) and metPET/VA EVA/LLDPE (metallized polyethylene terephthalate/ethylenevinyl acetate/linear low density polyethylene). Our assessment showed that both LE and DTS,TD techniques are valuable procedures. LE was evaluated as an alternative method with the advantage of being a simplified process. It was possible to measure the amount of D -limonene in the polymers using both methods. Correlation between methods was >82% and for the single layer polymers >92%. The respective sorption values obtained by the two methods were also found to be in good agreement. LE is simple and rapid to perform and, in general, gives slightly lower results compared to DTS,TS sorption tests conducted with adequate food simulants. The results indicate that the liquid extraction method is an excellent technique for the determination of sorbate concentration in polymeric structures. Copyright © 2004 John Wiley & Sons, Ltd. [source] Oriented thin films from soluble polythiophenesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2003Alberto Bolognesi Abstract The degree of orientation of thin films of eight different polymeric structures, belonging to the class of soluble polyalkylthiophenes (PATs) has been studied. Thin films of the polymers, obtained by spin coating onto glass substrates, were oriented by means of the rubbing technique. The degree of orientation is related to the regioregularity of the system: highly regioregular polymers can be oriented, while regiorandom materials are not oriented. The degree of orientation can be improved by thermal annealing of the oriented films. As a result of annealing, which was performed at different temperatures according to the thermal behavior of the polymers, it was possible to increase the polarization ratio for poly(3-decylthiophene) up to 12,13 as detected from the UV-vis spectra in polarized light. Moreover in the investigated PATs, both the key role of molecular weight and its distribution for achieving a high orientation degree has been assessed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Weak interactions in chain polymers [M(,- X)2L2], (M = Zn, Cd; X = Cl, Br; L = substituted pyridine) , an electron density studyACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2009Ruimin Wang The experimental electron-density distributions in crystals of five chain polymers [M(,- X)2(py)2] (M = Zn, Cd; X = Cl, Br; py = 3,5-substituted pyridine) have been obtained from high-resolution X-ray diffraction data sets (sin,,/, > 1.1,Å,1) at 100,K. Topological analyses following Bader's `Atoms in Molecules' approach not only confirmed the existence of (3, ,1) critical points for the chemically reasonable and presumably strong covalent and coordinative bonds, but also for four different secondary interactions which are expected to play a role in stabilizing the polymeric structures which are unusual for Zn as the metal center. These weaker contacts comprise intra- and inter-strand C,H...X,M hydrogen bonds on the one hand and C,X...X,C interhalogen contacts on the other hand. According to the experimental electron-density studies, the non-classical hydrogen bonds are associated with higher electron density in the (3, ,1) critical points than the halogen bonds and hence are the dominant interactions both with respect to intra- and inter-chain contacts. [source] Structure correlation study of four-coordinate copper(I) and (II) complexesACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2000Paul R. Raithby The geometries of four-coordinate CuI and CuII complexes in the Cambridge Structural Database (CSD) have been analysed systematically and compared using symmetry-deformation coordinates and principal component analysis. The observed stereochemistries have been rationalized in terms of the d -electron configurations, interligand repulsion and ,-bonding effects. The results confirm that the majority of four-coordinate copper(I) complexes in the CSD adopt tetrahedral geometries and deviations from tetrahedral symmetry are caused by the presence of chelating ligands or by the incorporation of copper centres into dimeric or polymeric structures. Four-coordinate copper(II) complexes generally adopt geometries close to square planar; this is particularly evident for bis(chelate) complexes where ,-bonding is important. Distortions towards tetrahedral geometries are attributable to steric interactions of bulky substituents in the bidentate ligands. [source] Copper(II) succinate complexes with 1,2-di-4-pyridylethane and 1,3-di-4-pyridylpropaneACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009M. J. González Garmendia The compounds poly[di-,4 -succinato-,2 -1,2-di-4-pyridylethane-dicopper(II)], [Cu2(C4H4O4)2(C12H12N2)]n, (I), and poly[di-,4 -succinato-,2 -1,3-di-4-pyridylpropane-dicopper(II)], [Cu2(C4H4O4)2(C13H14N2)]n, (II), exhibit polymeric structures with the dicopper units doubly bridged by bis-bidentate succinate groups and crosslinked by the separator bis(pyridyl) molecules. In (I), the molecule exhibits a centre of inversion located midway between the core Cu-dimer atoms and another that relates half of the bis(pyridyl)ethane ligand to the other half. Compound (II) has a similar molecular packing but with a doubled lattice constant and noncentrosymmetric core units. An antiferromagnetic interaction due to the dinuclear copper units was deduced from magnetic subsceptibility measurements, and spin triplet signals were detected in the electron paramagnetic resonance spectra for both compounds. [source] The anionic coordination polymer {K2[PtII2AgI8(2,2,-bipyridine)2(O2CCF3)14]}nACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009Zachary M. Hudson The trimetallic compound catena -poly[dipotassium(I) [bis(2,2,-bipyridine)di-,3 -trifluoroacetato-dodeca-,2 -trifluoroacetato-diplatinum(II)octasilver(I)]], K2[Pt2Ag8(C2F3O2)14(C10H8N2)2], forms an extended structure in the solid state. Electrostatic interactions involving the K+ ions play a key role in the formation of the extended structure in three dimensions. The AgI ions form one-dimensional coordination polymers, with alternating Ag2 and Ag6 units linked by CF3CO2, ligands. Pt...Pt interactions perpendicular to the one-dimensional polymerization axis provide another element of long-range order, and electrostatic interactions with K+ ions provide connectivity between adjacent polymeric structures. [source] Two polymeric structures with a benzene-1,2,4,5-tetracarboxylate ligand acting in ,2 - and ,4 -bridging modesACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Ana María Atria catena -Poly[[tetraaquabis(1H -pyrazole-,N2)nickel(II)] [[diaquabis(1H -pyrazole-,N2)nickel(II)]-,-benzene-1,2,4,5-tetracarboxylato-,2O1:O4] tetrahydrate], {[Ni(C3H4N2)2(H2O)4][Ni(C10H2O8)(C3H4N2)2(H2O)2]·4H2O}n, (I), and poly[[(,4 -benzene-1,2,4,5-tetracarboxylato-,4O1:O2:O4:O5)octakis(1H -pyrazole-,N2)dicobalt(II)] tetrahydrate], {[Co2(C10H2O8)(C3H4N2)8]·4H2O}n, (II), are polymeric compounds crystallizing in the space group P, with two independent metallic cations and one benzene-1,2,4,5-tetracarboxylate (btc) anion, each lying on symmetry centres. Individual coordination polyhedra are regular and the main differences are in the way the btc anion binds [,2 in (I) and ,4 in (II)], promoting a `chain-like' one-dimensional structure in (I) and a `sieve-like' two-dimensional motif in (II). [source] Powder study of poly[(,2 -2,2-dimethylpropane-1,3-diyl diisocyanide)-,2 -iodido-silver(I)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009Mwaffak Rukiah In order to explore the chemistry of the bidentate ligand 2,2-dimethylpropane-1,3-diyl diisocyanide and to investigate the effect of counter-ions on the polymeric structure of (2,2-dimethylpropane-1,3-diyl diisocyanide)silver(I) complexes, the title polymeric compound, [AgI(C7H10N2)]n, was synthesized by treatment of 2,2-dimethylpropane-1,3-diyl diisocyanide with AgI. X-ray powder diffraction studies show, as expected, a polymeric structure, similar to the very recently reported Cl, and NO3, analogues [AgX(C7H10N2)]n (X = Cl, or NO3,). In the title structure, the AgI centre is bridged to two adjacent AgI neighbours by bidentate 2,2-dimethylpropane-1,3-diyl diisocyanide ligands via the NC groups to form [Ag{CNCH2C(CH3)2CH2NC}]n chains. The iodide counter-ions crosslink the AgI centres of the chains to form a two-dimensional polymeric {[Ag{CNCH2C(CH3)2CH2NC}]I}n network. This study also shows that this bidentate ligand forms similar polymeric structures on treatment with AgX, regardless of the nature of the counter-ion X,, and also has a strong tendency to form polymeric complexes rather than dimeric or trimeric ones. [source] Physicochemical characterization of branched chain polymeric polypeptide carriers based on a poly-lysine backboneBIOPOLYMERS, Issue 3 2003I. B. Nagy Abstract A systematic study is reported on the physicochemical characteristics of two branched chain polymers (based on a poly- L -lysine backbone) with a general formula poly[Lys-(DL -Alam - Xi)], where X = Orn (OAK) or N -acetyl-Glu (Ac-EAK) and m , 3, using surface pressure and fluorescence polarization methods. These data are compared with those of the linear poly(L -Lys) from which OAK and Ac-EAK are derived. These two polymers show a moderate surface activity, able to form stable monomolecular layers at the air-water interface. Poly(L -Lys), the most hydrophilic, has the lowest surface activity. The interaction of these polymers with phospholipid bilayers either neutral or negatively charged was studied with vesicles labeled with two fluorescent probes: ANS and DPH. Results indicate that these polymers are able to accommodate in their internal structure, mainly through electrostatic interactions, a certain amount of ANS marker molecules, but fluorescence increases of the ANS-polypeptide complexes were so low that its influence in further polarization measurements could be discarded. After interaction with liposomes, these polymers induce an increase in the polarization of the probes, thus indicating a rigidification of the bilayers. Electrostatic forces seem to be very important in this interaction; cationic polymers are clearly more active, with PG-containing liposomes, than Ac-EAK. Moreover, in these assays poly(L -Lys) behaves as the more active compound. This fact is probably due to its major ability to form ,-helical structures that could insert easily in the bilayers. These results indicate that the polymeric structures studied can be used as carriers for biologically active molecules, because their interactions with bilayers remain soft and have a positive effect on the stability of the membranes. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 323,335, 2003 [source] Helicate Extension as a Route to Molecular WiresCHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2008David Schultz Abstract We describe the preparation of a helicate containing four closely spaced, linearly arrayed copper(I) ions. This product may be prepared either directly by mixing copper(I) with a set of precursor amine and aldehyde subcomponents, or indirectly through the dimerization of a dicopper(I) helicate upon addition of 1,2-phenylenediamine. A notable feature of this helicate is that its length is not limited by the lengths of its precursor subcomponents: each of the two ligands wrapped around the four copper(I) centers contains one diamine, two dialdehyde, and two monoamine residues. This work thus paves the way for the preparation of longer oligo- and polymeric structures. DFT calculations and electrochemical measurements indicate a high degree of electronic delocalization among the metal ions forming the cores of the structures described herein, which may therefore be described as "molecular wires". [source] | |||||||||||||||||||||||||