Search results for "BOND"
showing 10 items of 3527 documents
Ternary Polymer Solutions with Hydrogen Bonds, 2
2007
Experimental ternary phase diagrams for ternary systems CHL/PS-MAA/PVPy with diverse MAA contents have been determined by GPC. The presence of MAA in the copolymers gives rise to specific interactions, by hydrogen bond formation between both polymeric components, so strong that the isotherm for the system with the highest MAA content so far studied, CHL/PS-MAA(8%)/PVPy, is representative of a complex coacervation situation. By applying the theoretical background deduced by coupling the Flory-Huggins lattice model to the AET developed for ternary polymeric systems SPP with specific intermolecular interactions (via hydrogen bonds), free energy surfaces for the CHL/PS-MAA/PVPy systems are cons…
Collision-Induced Dissociation of Imidazolium-Based Zwitterionic Liquids
2009
Fragmentation pathways of some imidazolium based zwitterionic liquids—3-(3-alkyl-1-imidazolio)-propane sulfonates and 3-(2-methyl-3-alkyl-1-imidazolio)-propane sulfonates—have been studied by tandem electrospray mass spectrometry and collision-induced dissociation. The relative abundances of the lowest energy fragment ions depend on the length of the alkyl chain at the IIN of the imidazolium ring and the cone voltage. The first fragment ions originate from the scission of Cnon aromatic–N bond of compounds investigated, but with increasing collision energy, scission of C–C bonds occurs. Aggregates of the general formula [(M + H) x + (M) y]+ ( x;y = 1–2) formed. Methyl substituted zwitterion…
Electrospray Ionization Mass Spectrometry of Non-Covalent Complexes Formed between N-Alkylimidazolium-Containing Zwitterionic Sulfonates and Protonat…
2015
This paper describes non-covalent complexes between zwitterionic 3-(1-alkyl-3 N-imidazolio)-propane-1-sulfonates and different amines. Electrospray ionization (ESI) mass spectrometry and collision-induced dissociation were used to measure the stability of such complexes in solution and in the gas phase. Generally, zwitterionic sulfonates formed more abundant complexes with protonated 5-methylcytosine (5-MCH) than with aliphatic amines. The results show that the association constants and half-dissociation threshold energies of these complexes nonlinearly depend on the alkyl chain length of the zwitterion. It is shown that the complexes with the lowest stability exist in acetonitrile solutio…
Combretastatin Analogs via Hydration of Stilbene Derivatives
1993
Hydration of the double bond of some stilbene congeners of Picea abies bark by TiCl4·NaBH4 reagent is described. Five racemic 1,2-diphenylethanol derivatives (9–13), structurally related to (R)-(·)-combretastatin [(R)-1], have been obtained and characterized mainly by 13C- and 1H-NMR as well as mass spectrometry. The antileukemic activity of each compound has preliminarily been tested by the mouse leukemia L1210 system. Compound 10 has been synthesized by Friedel-Crafts acylation.
Molecular Parameters of Hyperbranched Polymers Made by Self-Condensing Vinyl Polymerization. 2. Degree of Branching
1997
Using a modified definition, the average degree of branching, , the fraction of branchpoints, , as well as the fractions of various structural units are calculated as a function of conversion of double bonds for hyperbranched polymers formed by self-condensing vinyl polymerization (SCVP) of monomers (or “inimers”) with the general structure AB*, where A is a vinyl group and B* is an initiating group. The results are compared to those for the polycondensation of AB2-type monomers. At full conversion, is somewhat smaller for SCVP ( ∞ ≈ 0.465) than for AB2 systems ( ∞ = 0.5). There are two kinds of linear groups in SCVP whereas there is only one kind in AB2 systems. Since there are two differe…
LC Ionomers with Phosphonate Groups and Their Multilayer Build-Up
2002
This paper describes the synthesis of new liquid-crystalline (LC) ionomers (semiflexible LC mainchain polymers with ionic groups as side groups) by polycondensation of substituted malonates with mesogenic diols. Phosphonic acids were used as negative groups, and phosphonium and ammonium ions as positive groups. The presence of these ionic groups leads to gelation (physical crosslinking) of the polymers, which display a rubbery consistency. As expected from the reference polymers without an ionic group, all polymers show smectic phases. These phases are destabilized by bulky side groups (e.g., phosphonium ions or phosphonic acid esters). They are, however, stabilized by phosphonic acid group…
Redox Materials by the Covalent Entrapment of Redox-Active Dirhodium(II,II) Species in a Siloxane Network
2004
Hydrolysis and polycondensation of the coupling agent (aminopropyl)triethoxysilane (APS), axially coordinated to the redox-active complex [Rh 2 (form) 2 (CH 3 COO) 2 -(APS) 2 ], lead to the insertion of redox-active inorganic microdomains into a siloxane network; the new polymers undergo cyclic redox reactions indicating that dirhodium(II,II) centres retain their redox activity even when incorporated into siloxane networks.
Self-organized nanostructures of poly(4-vinylpyridine), polyaniline and polyamides due to metal complexation
2002
Comb-shaped supramolecules are constructed using flexible polymers and semi-rigid conjugated undoped or doped conjugated polymers upon complexing Zinc dodecyl benzene sulphonate, Zn(DBS) 2 . Self-organized nanostructures are formed in the bulk due to competing attractive interactions (coordination or water mediated hydrogen bonding) and repulsive polar/nonpolar interactions, showing characteristic long periods of ca. 30 A.
Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes
2008
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including kappa 1-, mu-1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)].1/3 MeOH contains dinuclear cations with three mu-1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density fun…
Copper(II) complexes of 3-aminopropanols. Synthesis and structure of (3-aminopropanolato)formatocopper(II)
1987
Abstract The crystal and molecular structure of the title compound has been determined from single-crystal X-ray data and refined to a final R value of 0.030 for 971 reflections. The compound crystallizes in the monoclinic space group P21/c with two dimeric molecules in a cell of dimensions a=856.9(1), b= 887.7(1), c=837.0(1) pm and β=99.55(1)°. The blue crystals of Cu(ap)(HCOO) (ap=3-aminopropanolato ion) are made of centrosymmetric dialkoxy bridged dimers (Cu…Cu 296.4(1) pm). The dimers are polymerized along the c axis into chains via two NHO hydrogen bonds (Cu…Cu 547.9(1) pm). These chains are joined together along the b axis by CuOCOCu bridges and NHO hydrogen bonds (Cu…Cu 462.2(1) pm…