Search results for "Titration"
showing 10 items of 312 documents
Supramolecular Linear-g-Hyperbranched Graft Polymers: Topology and Binding Strength of Hyperbranched Side Chains
2013
Complex, reversible hyperbranched graft polymer topologies have been obtained by spontaneous self-assembly. Well-defined adamantyl- and β-cyclodextrin-functionalized polymers were employed to generate linear-g-(linear–hyperbranched) supramolecular graft terpolymers. For this purpose the synthesis of monoadamantyl-functionalized linear polyglycerols (Ada-linPG) and hyperbranched polyglycerols (Ada-hbPG) as well as poly(ethylene glycol)-block-linear polyglycerol (Ada-PEG-b-linPG) and poly(ethylene glycol)-block-hyperbranched poly(glycerol) (Ada-PEG-b-hbPG) block copolymers was established. Isothermal titration calorimetry (ITC) with β-cyclodextrin revealed a shielding effect of hyperbranched …
Effect of pH Variations on the Properties of Cyclodextrin‐Calixarene Nanosponges
2019
The pH-responsive properties of cyclodextrin-calixarene nanosponge co-polymeric materials have been investigated. In particular, ISE-H+ potentiometric titrations were carried out in order to evaluate the acid-base properties and the actual amount of ionizable sites present in the materials. Moreover, the relevant pH-dependent adsorption abilities were evaluated towards a set of selected model organic pollutant molecules by means of adsorption tests and by studying the corresponding adsorption isotherms. The latter ones could be suitably described by means of the Freundlich model. The whole of the experimental results enabled us to clarify some general aspects of the microscopic behavior of …
Binding ability of N-Para-amino-phenylsulfonyl derivatives of amino acids. Potentiometric and spectroscopic studies of Cu(II) complexes
1995
Abstract N-Para-amino-phenylsulfonyl derivatives of amino acids are very effective ligands for Cu(II) ions. Potentiometric and spectroscopic results have shown that Cu(II) ions are able to deprotonate and bind to sulfonamide nitrogen below pH 5 to form stable mono- and bis-[N − , COO − ] chelates. The basicity of sulfonamide nitrogen is lower than peptide amide nitrogen and no distinct anchoring site is necessary to promote the amide nitrogen deprotonation.
Coordination of copper(II) ions by α,β-dehydro-dipeptides. Potentiometric and spectroscopic study
1991
Abstract Potentiometric and spectroscopic data have shown that the double bond within dehydro-peptides considerably affects their behaviour as ligands relative to their saturated parents, with proton and copper(II) ions.
Cyclic Analogs of Desferrioxamine E Siderophore for 68Ga Nuclear Imaging: Coordination Chemistry and Biological Activity in Staphylococcus aureus
2021
As multidrug-resistant bacteria are an emerging problem and threat to humanity, novel strategies for treatment and diagnostics are actively sought. We aim to utilize siderophores, iron-specific strong chelating agents produced by microbes, as gallium ion carriers for diagnosis, applying that Fe(III) can be successfully replaced by Ga(III) without losing biological properties of the investigated complex, which allows molecular imaging by positron emission tomography (PET). Here, we report synthesis, full solution chemistry, thermodynamic characterization, and the preliminary biological evaluation of biomimetic derivatives (FOX) of desferrioxamine E (FOXE) siderophore, radiolabeled with 68Ga …
Synthesis and Structural Characterization of a Cyclen-Derived Molecular Cage
2015
Reaction of a tetrafunctionalized cyclen derivative containing four aldehyde groups with an appropriate diamine followed by reduction and demetalation highly efficiently affords a bis(cyclen)-derived molecular cage. Potentiometric investigations show that this compound forms dimetallic complexes with copper(II), with the two metal ions selectively coordinated to the cyclen units. X-ray crystallography indicates that these complexes could give rise to new cascade complexes after incorporation of anions between the metal centers.
Substituent effects on axle binding in amide pseudorotaxanes: comparison of NMR titration and ITC data with DFT calculations
2012
The binding behaviour of differently substituted diamide axle molecules to Hunter/Vögtle tetralactam macrocycles was studied with a combination of NMR titration, isothermal titration calorimetry (ITC) experiments and calculations employing density functional theory (DFT), along with dispersion-corrected exchange-correlation functionals. Guests with alkyl or alkenyl chains attached to the diamide carbonyl groups have a significantly higher binding affinity to the macrocycle than guests with benzoyl amides and their substituted analogues. While the binding of the benzoyl and alkenyl substituted axles is enthalpically driven, the alkyl-substituted guest binds mainly because of a positive bindi…
Tritopic phenanthroline and pyridine tail-tied aza-scorpiands
2010
The synthesis of two new tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties have been linked with 2,6-dimethylpyridine (L1) or 2,9-dimethylphenanthroline (L2) units is reported for the first time. Their acid-base behaviour and Zn(2+) coordination chemistry have been studied by pH-metric titrations, molecular dynamic calculations, NMR, UV-Vis and steady-state fluorescence techniques. L1 and L2 behave, respectively, as hexaprotic and heptaprotic bases in the experimental conditions used (298.1 +/- 0.1 K, 0.15 mol dm(-3) NaCl, pH range under study 2.0-11.0). These ligands are able to form mono-, bi- and trinuclear Zn(2+) co…
Co-ordination of copper(II) ions by prolyl-α,β-dehydroamino acids: comparative studies and general considerations
1996
Potentiometric and spectroscopic measurements and theoretical calculations have revealed that α,β-dehydroamino acid residues have a considerable effect on the co-ordination ability of an adjacent amide nitrogen towards Cu2+ ions. Also the side chain of such residues affects the stability constants and, in some cases, the binding mode of short peptides containing α,β-dehydroamino acid residues. The theoretical calculations showed that all dehydroamino acids except α,β-dehydroalanine tend to bend a peptide chain towards a turn conformation. This has a very strong impact on the co-ordination ability of a dehydropeptide ligand.
Efficient Self-Assembly of Di-, Tri-, Tetra-, and Hexavalent Hosts with Predefined Geometries for the Investigation of Multivalency
2015
Coordination-driven self-assembly of differently shaped di- to hexavalent crown-ether host molecules is described. A series of [21]crown-7- and [24]crown-8-substituted bipyridine and terpyridine ligands was synthetized in a "toolbox" approach. Subsequent coordination to 3d transition metal and ruthenium(II) ions provides an easy and fast access to host assemblies with variable valency and pre-defined orientations of the crown-ether moieties. Preliminary isothermal calorimetry (ITC) titrations provided promising results, which indicated the host complexes under study to be suitable for the future investigation of multivalent and cooperative binding. The hosts described herein will also be su…