Search results for "ionic"
showing 10 items of 2016 documents
Solid‐State Anion–Guest Encapsulation by Metallosupramolecular Capsules Made from Two Tetranuclear Copper(II) Complexes
2007
A new cationic tetranuclear copper(II) complex self-assembles from one 1,3-phenylenebis(oxamato) (mpba) bridging ligand and four CuII ions partially blocked with N,N,N′,N′-tetramethylethylenediamine (tmen) terminal ligands. In the solid state, two of these tetracopper(II) oxamato complexes of bowl-like shape and helical conformation then serve as a building block for the generation of either hetero- (MP) or homochiral (MM/PP) dimeric capsules depending on the nature of the encapsulated anion guest, perchlorate or hexafluorophosphate. The overall magnetic behaviour of these metallosupramolecular capsules does not depend on the nature of the encapsulated anion guest, but it is consistent with…
A new palladium(II)-catalyzed [3,3] aza-Claisen rearrangement of 3-allyloxy-5-aryl-1,2,4-oxadiazoles
2011
Abstract A new efficient palladium(II)-catalyzed [3,3] aza-Claisen, formal sigmatropic rearrangement of 3-allyloxy-5-aryl-1,2,4-oxadiazoles was developed. The mechanism was studied by analyzing the regiochemical and stereochemical course of the reaction. The results obtained indicated the intervention of a cationic pallada-cycle similar to the one postulated for the Cope rearrangement of 1,5-dienes.
The effects of structural changes on the anti-microbial and anti-proliferative activities of diimidazolium salts
2017
An array of diimidazolium salts has been synthesized and used to investigate their anti-microbial and anti-proliferative activities. In particular, salts based on the 3,30-di-n-alkyl-1,10-(1,n-phenylenedimethylene)- diimidazolium cation and differing in the alkyl chain length on the imidazolium ion, the isomeric substitution on the aromatic spacer and in the anion nature were used. The anti-proliferative activity was evaluated against cervical (HeLa), colon adenocarcinoma (HT-29) and breast (SKBR3) cancer cell lines. In the latter case, also a morphological assessment after treatment with salts was performed. All salts were tested for their hemolytic activity against human erythrocytes. On …
Bioresponsive poly(amidoamine)s designed for intracellular protein delivery.
2013
Poly(amidoamine)s with bioreducible disulfide linkages in the main chain (SS-PAAs) and pH-responsive, negatively charged citraconate groups in the sidechain have been designed for effective intracellular delivery and release of proteins with a net positive charge at neutral pH. Using lysozyme as a cationic model protein these water soluble polymers efficiently self-assemble into nanocomplexes by charge attraction. At pH 5 (the endosomal pH) the amide linkages connecting the citraconate groups in the sidechains of the SS-PAAs are hydrolyzed by intramolecular catalysis, resulting in expulsion of the negative citraconate groups and formation of protonated amine groups, resulting in charge reve…
The introduction of fluorine atoms or trifluoromethyl groups in short cationic peptides enhances their antimicrobial activity
2006
The effect of introducing fluorine atoms or trifluoromethyl groups in either the peptidic chain or the C-terminal end of cationic pentapeptides is reported. Three series of amide and ester peptides were synthesised and their antimicrobial properties evaluated. An enhanced activity was found in those derivatives whose structure contained fluorine, suggesting an increase in their hydrophobicity.
ChemInform Abstract: UEBER ARSEN-HALTIGE HETEROCYCLEN 3. MITT. KRISTALLSTRUKTUR VON 2,6-DIMETHYL-4,4-DIPHENYL-1,4-OXOARSENANIUMBROMID-MONOHYDRAT
1975
Abstract The crystal structure of the title compound has been determined from single crystal X-ray data and refined to a conventional R factor of 0.046. The coordination of the As atom is tetrahedral with a mean As—C distance of 1.92 A. The six-membered heterocycle has chair conformation with two equatorial methyl and one equatorial and one axial phenyl substituent. The transannular 1,4-As⋯O distance is 3.11 A, interactions are discussed. The connection of the structure is more van der Waals than ionic type. Some unspecific gaps are statistically occupied by one molecule of crystal water.
Protonation constants and association of polycarboxylic ligands with the major components of seawater
2000
Apparent protonation constants, log βjH*, of 11 carboxylic acids were determined potentiometrically ([H+]-glass electrode) in artificial seawater containing six of the major components (Na+, K+, Mg2+, Ca2+, Cl-, and SO42-) at different salinities: S (‰) = 5, 15, 25, 35, 45. Values of log βjH* were fitted by the simple polynomial equation log βjH* = log TβjH + a1S1/2 + a2S + a3S3/2 (log TβjH = protonation constants at infinite dilution; a1, a2, a3 = empirical parameters), for mono-, di-, and tricarboxylates. For carboxylic anions with charge < −3, a better fit was obtained using the equation log βjH* = log TβjH + b1I + b0z* log(1 + b2I) (b0, b1, b2 = empirical parameters, z* = square sum of…
Interaction of the Dioxouranium(VI) Ion with Aspartate and Glutamate in NaCl(aq) at Different Ionic Strengths
2005
The formation of complexes species of the dioxouranium(VI) ion with aspartic and glutamic acids was studied in the pH range of 3 to 6 at 25 °C by potentiometric measurements (H+−glass electrode). R...
Single chain magnet behaviour in an enantiopure chiral cobalt(II)–copper(II) one-dimensional compound
2010
The self-assembly of an enantiomerically pure, chiral dianionic oxamatocopper(II) complex with cobalt(II) ions leads to neutral oxamato-bridged heterobimetallic chains that combine chirality and slow magnetic relaxation, providing thus the first example of ‘‘chiral single chain magnets (CSCMs). Ruiz Garcia, Rafael, Rafael.Ruiz@uv.es ; Lloret Pastor, Francisco, Francisco.Lloret@uv.es
Self-Assembly of Zr(C2O4)44– Metallotectons and Bisimidazolium Cations: Influence of the Dication on H-Bonded Framework Dimensionality and Material P…
2011
Assemblies involving [Zr(C2O4)4]4– metallotectons (C2O42– = oxalate) and linear, flexible, or V-shaped organic cations (H2-Lx)2+ derived from the 1,4-bisimidazol-1-ylbenzene molecule have been envisioned to elaborate porous frameworks based on ionic H-bonds. Five architectures of formula [{(H2-L1)2Zr(C2O4)4}·2H2O] (1), [{(H2-L2)2Zr(C2O4)4}·6H2O] (2), [{(H2-L3)2Zr(C2O4)4}·6H2O] (3), [{(H2-L4)2Zr(C2O4)4}·H2O] (4), and [{(H2-L5)2Zr(C2O4)4}·6H2O] (5) (with L1 = p-bis(imidazol-1-yl)benzene, L2 = p-bis(2-methylimidazol-1-yl)benzene, L3 = p-bis(imidazol-1-yl)-2,5-dimethylbenzene, L4 = p-bis(imidazol-1-ylmethyl)benzene, L5 = m-bis(imidazol-1-yl)benzene) have been obtained; 1–3, and 5 show an open-f…