Influence of strong transannular N → P interaction on acidity of cyclenphosphine sulfide

International audienceThe acid-base behavior of cyclenphosphine sulfide (cyclenPS) is appreciably different from that of cyclamphosphine sulfide (cyclamPS). The cyclenPS shows five acid functionalities compared to four for cyclamPS. The fifth acidic group in cyclenPS corresponds to the formation of a stable amidure in aqueous solution (pK(a5) = 12.3). This behavior is due to the strong transannular N → P interaction. The deprotonation sequences were established by 31P-NMR and confirmed by modelling of cyclenPS

XAS, ESR and potentiometric studies of three dinuclear N,N′-para-xylylenebis(tetraazamacrocycle)copper(II) complexes - X-ray crystal structure of [N,N′-p-xylylenebis(cyclen)]copper(II)

cited By 21International audienceDicopper complexes with N,N′-p-xylylenebis(cyclam or cyclen) and with the heteroditopic N,N′-p-xylylenebis(cyclam-cyclen) were synthesized. An X-ray study of the N,N′- p-xylylenebis(cyclen)dicopper complex showed that the copper(II) ion is five-coordinate with an H2O molecule in apical position. With this ligand, a polymeric chain was also obtained in the presence of KSCN. The terminal donor atoms of the bridging NCS- anion are coordinated in apical position to the square-pyramidal copper(II) ion. Two alternating kinds of Cu2L4+ moieties are present in the chain, the first with two N4S chromophores and the second with two N5 chromophores. EXAFS and XANES results are in agreement with a five-coordinate copper ion in the cyclen unit and a six-coordinate copper ion in the cyclam unit. Thermodynamic constants were determined by potentiometry. The existence of dinuclear Cu2L4+ species (ligand/metal ratio < 1) and mononuclear CuLHn(2+n)+ species (ligand/metal ratio > 1) were confirmed by an ESR study at variable pH. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003

Magnetic measurements, UV-Vis spectroscopy, and XAS of dinuclear nickel(II) complexes of bistetraazamacrocycles

cited By 11International audienceThe nickel(II) complexes of N,N′-xylylenebis(tetraazamacrocycles) have been isolated. The description of these dinuclear bismacrocyclic complexes have been carried out by means of magnetic measurements and spectrophotometric experiments (UV-Vis). The metal environment and the ligand shape have been specified by XANES and EXAFS experiments, since attempts to obtain suitable crystals failed. © 2004 Elsevier Ltd. All rights reserved

XAS, ESR and potentiometric studies of three dinuclear N,N′-para-xylylenebis(tetraazamacrocycle)copper(II) complexes - X-ray crystal structure of [N,N′-p-xylylenebis(cyclen)]copper(II)

cited By 21International audienceDicopper complexes with N,N′-p-xylylenebis(cyclam or cyclen) and with the heteroditopic N,N′-p-xylylenebis(cyclam-cyclen) were synthesized. An X-ray study of the N,N′- p-xylylenebis(cyclen)dicopper complex showed that the copper(II) ion is five-coordinate with an H2O molecule in apical position. With this ligand, a polymeric chain was also obtained in the presence of KSCN. The terminal donor atoms of the bridging NCS- anion are coordinated in apical position to the square-pyramidal copper(II) ion. Two alternating kinds of Cu2L4+ moieties are present in the chain, the first with two N4S chromophores and the second with two N5 chromophores. EXAFS and XANES results are in agreement with a five-coordinate copper ion in the cyclen unit and a six-coordinate copper ion in the cyclam unit. Thermodynamic constants were determined by potentiometry. The existence of dinuclear Cu2L4+ species (ligand/metal ratio < 1) and mononuclear CuLHn(2+n)+ species (ligand/metal ratio > 1) were confirmed by an ESR study at variable pH. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003

Etude IRM in vivo d’une sonde cardiaque basée sur des complexes β-cyclodextrines-Gd(III)

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A benzimidazole functionalised DO3A chelator showing pH switchable coordination modes with lanthanide ions.

The synthesis of a new macrocyclic chelator incorporating a benzimidazole heterocycle is reported. Lanthanide complexes with macrocyclic chelators based on 1,4,7,10-tetra(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DOTA) and 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DO3A) are of interest in luminescent, radiopharmaceutical and magnetic resonance (MR) biomedical imaging applications. The benzimidazole DO3A chelator allows for sensitisation of europium(iii), terbium(iii) and ytterbium(iii) luminescence by the heterocycle and also shows a pH dependent coordination change due to protonation of the chelator (pKa = 4.1 for the europium(iii) complex). The thermodynamic stability of the complexes has been investigated by potentiometric titration with the gadolinium(iii) complex showing significantly higher stability than the zinc(ii) complex, where log βZnLH = 28.1 and log βGdLH = 32.1

A benzimidazole functionalised DO3A chelator showing pH switchable coordination modes with lanthanide ions.

The synthesis of a new macrocyclic chelator incorporating a benzimidazole heterocycle is reported. Lanthanide complexes with macrocyclic chelators based on 1,4,7,10-tetra(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DOTA) and 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DO3A) are of interest in luminescent, radiopharmaceutical and magnetic resonance (MR) biomedical imaging applications. The benzimidazole DO3A chelator allows for sensitisation of europium(iii), terbium(iii) and ytterbium(iii) luminescence by the heterocycle and also shows a pH dependent coordination change due to protonation of the chelator (pKa = 4.1 for the europium(iii) complex). The thermodynamic stability of the complexes has been investigated by potentiometric titration with the gadolinium(iii) complex showing significantly higher stability than the zinc(ii) complex, where log βZnLH = 28.1 and log βGdLH = 32.1