Optimization of the selectivity and rate of copper radioisotope complexation: formation and dissociation kinetic studies of 1,4,8-trimethylcyclam-based ligands with different coordinating pendant arms

2018 ◽  
Vol 42 (14) ◽  
pp. 11908-11929 ◽  
Author(s):  
Monika Paúrová ◽  
Tomáš David ◽  
Ivana Císařová ◽  
Přemysl Lubal ◽  
Petr Hermann ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Pendant Arm ◽  
Dissociation Kinetic ◽  
Pendant Arms

Influence of coordinating pendant arm character on selectivity and rate of copper(ii) complexation was investigated to optimize ligands for radiomedicinal use.

A macrocyclic ligand able to bind gallium(iii) by preorganized pendant arms; coordination and kinetic studies

2005 ◽  
pp. 485 ◽  
Author(s):  
Gianluca Ambrosi ◽  
Alessia Boggioni ◽  
Mauro Formica ◽  
Vieri Fusi ◽  
Luca Giorgi ◽  
...  
Keyword(s):  
Macrocyclic Ligand ◽  
Kinetic Studies ◽  
Pendant Arms

A new family of NxOy pyridine-containing macrocycles: Synthesis and characterization of their Y(III), Ln(III), Zn(II), and Cd(II) coordination compounds

2004 ◽  
Vol 82 (3) ◽  
pp. 437-447 ◽  
Author(s):  
Carlos Lodeiro ◽  
Rufina Bastida ◽  
Emilia Bértolo ◽  
Adolfo Rodríguez
Keyword(s):  
Schiff Base ◽  
Macrocyclic Ligand ◽  
Macrocyclic Ligands ◽  
New Family ◽  
Pendant Arm ◽  
Starting Point ◽  
Wide Range ◽  
Imine Bond ◽  
Pendant Arms

Reaction between 2,6-bis(2-formylphenoxymethyl)pyridine and N,N-bis(3-aminopropyl)methylamine or tris(2-aminoethyl)amine has been used as the starting point for the synthesis of seven oxa-aza macrocyclic ligands, five of them never reported previously. They all feature different pendant arms, which provide a wide range of coordination possibilities. The Schiff base macrocycles L1 and L4 and their reduced ligands L2 and L5 are derived from 2,6-bis(2-formylphenoxymethyl)pyridine and tris(2-aminoethyl)amine or N,N-bis(3-aminopropyl)methylamine, respectively. The reaction of L1 with salicylaldehyde forms L3, which features an imine bond in the pendant arm. The ligand L5 has been the precursor for the pendant-armed L6 and L7, by alkylation of the free NH groups with methyl-imidazole or methyl-indole. By a template or a nontemplate approach, we have synthesized different mono- and dinuclear complexes with Y(III), Ln(III), Zn(II), and Cd(II) cations. Both the free macrocyclic ligands and their corresponding metal complexes have been characterized by microanalysis, IR, UV–vis, 1H and 13C NMR spectroscopy, FAB mass spectrometry, MS electrospray, and conductivity measurements.Key words: Schiff-base macrocycle, template synthesis, macrocyclic ligand complexes, lanthanide(III) complexes.

Thermodynamic and Kinetic Studies of Lanthanide(III) Complexes with H5do3ap (1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic-10-(methylphosphonic Acid)), a Monophosphonate Analogue of H4dota

2005 ◽  
Vol 70 (11) ◽  
pp. 1909-1942 ◽  
Author(s):  
Petr Táborský ◽  
Přemysl Lubal ◽  
Josef Havel ◽  
Jan Kotek ◽  
Petr Hermann ◽  
...  
Keyword(s):  
Solution Structure ◽  
Kinetic Studies ◽  
Lanthanide Ions ◽  
Methylphosphonic Acid ◽  
Bulk Solution ◽  
Complex Species ◽  
Pendant Arm ◽  
Trivalent Lanthanide ◽  
Ring Nitrogen ◽  
Kinetics Of

Solution properties of complexes of a new H4dota-like ligand containing three acetate and one methylphosphonate pendant arms (H5do3ap, H5L) were studied. The ligand exhibits a high last dissociation constant (pKA = 13.83) as a consequence of the presence of phosphonate moiety. In solution, successive attachment of protons leads to several reorganizations of protonation sites and the neutral zwitterionic species H5do3ap has the same solution structure as in the solid state, where the nitrogen atom binding methylphosphonate and the opposite nitrogen atoms are protonated. Stability constants with Na+ and trivalent lanthanide ions (La3+, Ce3+, Eu3+, Gd3+, Lu3+) and Y3+ have been determined. The constants are comparable or higher than those of H4dota due to the higher overall basicity of H5do3ap. Formation of the stable protonated complexes, as well as complexes with the L:M = 1:2 stoichiometry, was proved. Formation and decomplexation kinetics of the Ce3+ and Gd3+ complexes were investigated. The mechanism of formation of the H5do3ap complexes is similar to that observed for H4dota complexes and the complex species with mono- or diprotonated ligand on the cyclen ring are considered as the reaction intermediates. Acid-assisted decomplexation of H5do3ap complexes is faster in comparison with those of H4dota. This is caused by higher basicity of the phosphonate pendant arm and the ring nitrogen atoms, which facilitates the proton transfer from the bulk solution to the nitrogen atoms of cyclen ring.

scholarly journals Magnetic Properties of Fe(II) Complexes of Cyclam Derivative with One p-Aminobenzyl Pendant Arm

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 366
Author(s):  
Bohuslav Drahoš ◽  
Peter Antal ◽  
Ivan Šalitroš ◽  
Radovan Herchel
Keyword(s):  
Crystal Structure ◽  
Magnetic Properties ◽  
High Spin ◽  
Spin Crossover ◽  
Crystal Packing ◽  
Theoretical Calculations ◽  
High Spin State ◽  
Magnetic Data ◽  
Pendant Arm ◽  
Pendant Arms

In order to prepare an Fe(II) spin crossover (SCO) complex that could be consequently modified to a bimetallic coordination compound that possesses another magnetic property of interest, a specially designed ligand L-NH2 (1-(4-aminobenzyl)-4,11-bis(pyridine-2-ylmethyl)- 1,4,8,11-tetraazacyclotetradecane) was prepared. This ligand consists of a macrocyclic cyclam part containing two 2-pyridylmethyl pendant arms (expecting SCO upon Fe(II) complexation) and one p-aminobenzyl pendant arm with an NH2 group. The presence of this group enables the consequent transformation to various functional groups for the selective complexation of other transition metals or lanthanides (providing the second property of interest). Furthermore, the performed theoretical calculations (TPSSh/def2-TZVP) predicted SCO behavior for the Fe(II) complex of L-NH2. Thus, Fe(II) complexes [Fe(L-NH2)](ClO4)2 (1) and [Fe(L-NH2)]Cl2·6H2O (2) were synthesized and thoroughly characterized. Based on the crystal structure of an isostructural analogous Ni(II) complex [Ni(L-NH2)]Cl2·6H2O (3), the coordination number six was confirmed with an octahedral coordination sphere and a cis-arrangement of the pyridine pendant arms. The measured magnetic data confirmed the high-spin behavior of both compounds with large magnetic anisotropy (D = 17.8 for 1 and 20.9 cm−1 for 2 complemented in both cases also with large rhombicity), though unfortunately without any indication of the SCO behavior with decreasing temperature. The lack of SCO can be ascribed to the crystal packing and/or the non-covalent intermolecular interactions stabilizing the high-spin state in the solid state.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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