Henri Handel

Bis-aminals: efficient tools for bis-macrocycle synthesis

Tetraazamacrocyclic bis-aminals prove to be excellent tools for the synthesis of symmetrical, dissymmetrical or functionalized bis-tetraazamacrocycles. The key feature of the process is the separation of insoluble mono- or bis-quaternary ammonium salts from solution during the course of the alkylation reaction.

A new route to cyclen, cyclam and homocyclen

Abstract Cyclen, cyclam and homocyclen have been synthesized from the corresponding butanedione-protected linear tetramines. The cyclization step is followed by a facile deprotection of the rigidifying moiety.

Accelerating water exchange for GdIII chelates by steric compression around the water binding site

The water exchange process was accelerated for nine-coordinate, monohydrated macrocyclic GdIII complexes by inducing steric compression around the water binding site; the increased steric crowding was achieved by replacing an ethylene bridge of DOTA4- by a propylene bridge; in addition to the optimal water exchange rate, the stability of [Gd(TRITA)(H2O)]- is sufficiently high to ensure safe medical use which makes it a potential synthon for the development of high relaxivity, macromolecular MRI contrast agents.

GENERAL ROUTE FOR THE SYNTHESIS OF MONO N-ALKYLATED DERIVATIVES OF TETRAAZAMACROCYCLES

Abstract The selective synthesis of mono N-substituted derivatives of tetraazamacrocycles can be achieved using a new boron triprotection easily removed after alkylation.

Condensation of glyoxal with triethylenetetraamine. Stereochemistry, cyclization and deprotection

Abstract A mixture of bis-aminal isomers was obtained from aqueous glyoxal-triethylenetetraamine condensation. The irreversible isomerization of the species was observed and a new synthesis of cyclen proposed.

Mono N-alkylation and N-acylation of cyclen and cyclam via their metaltricarbonyl complexes (M = Cr, Mo)

Abstract Reaction of metaltricarbonyl complexes of cyclen and cyclam with enolisable aldehydes or acid chlorides yields, after removal of the protecting M(CO) 3 moiety, selectively mono N-functionalized derivatives.

Preconcentration of trace metals from sea water with the chelating resin Chelamine

Abstract The complexing properties (capacity, pH effect, breakthrough curve) of the chelating resin Chelamine, containing a pentamine ligand, were investigated. The resin was used in a column procedure for the preconcentration of Cd(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) from deionized water and sea water and the recoveries were 93–105 and 91–102%, respectively. The absolute blanks varied from less than 0.6 ng for Cd to 11 ng for Cu, permitting the determination of the above six metals in oceanic water. The accuracy of the method was demonstrated by replicate analyses of the marine reference material CASS-2. The high selectivity of the resin leads to low concentration of alkali and alkaline earth metal ions in the acidic eluate.

Column preconcentration of trace metals from sea-water with macroporous resins impregnated with lipophilic tetraaza macrocycles

Macroporous resins impregnated with lipophilic tetraaza macrocyclic derivatives were used for the uptake and enrichment of trace metals from sea-water prior to their determination by electrothermal atomic absorption spectrometry. The effects of the size of the macrocycle cavity, the support used for impregnation, the pH of the extraction and the parameters of the back-extraction were studied in a column process. The preconcentration of trace metals (Cd, Cu, Mn, Ni, Pb and Zn) from de-ionized water and sea-water was investigated. Satisfactory results were obtained for Cd, Mn, Pb and Zn with an average recovery of 98 ± 8%. Absolute blanks are in the range 1–10 ng and the detection limit varies from 0.7 ng for Cd to 15 ng for Pb. The accuracy of the method was demonstrated by replicate analyses of the National Research Council of Canada marine reference material NASS-2 (open ocean sea-water). The precision is better than 15%(1σ). The selectivity of the resin for Cd, Cu, Mn, Ni, Pb and Zn over NaI, CaII and MgII was studied.

Host–guest interaction between cyclen based macrotricyclic ligands and phosphate anions. A potentiometric investigation

The host-guest interaction between orthophosphate, pyrophosphate and triphosphate anions and three cyclen based macrotricyclic ligands possessing ortho- (TOC), meta- (TMC) and para-xylenyl (TPC) linkers was investigated by potentiometric measurements. The ternary species present in solution and their stability constants have been determined. The different behaviours are explained in terms of hydrogen bond formation and coulombic attraction between the organic host and the inorganic guest. The selectivity, illustrated with species distribution diagrams, is discussed. The results unambiguously showed the importance of the distance between the two cyclen cores and emphasized the increasing of the triphosphate species selectivity together with the cavity size of the ligand. A comparison of the present results with those obtained with their mono-bridged homologues is also discussed.

Application of a tetraaza macrocycle immobilized on an organic polymer to the determination of trace amounts of manganese in sea water

Abstract Poly(vinylbenzyltetraaza-1,4,8,11-cyclotetradecane) was synthesized and used for the preconcentration of manganese from sea water prior to its determination by graphite furnace atomic absorption spectrometry. The improvement in the porosity of this new polymer has a significant effect on the rates of the extraction and back-extraction steps in comparison with previously described polymers. Swelling, capacity and pH effects were studied by the batch technique. The validity of the method is demonstrated by comparison with the quinolin-8-ol-chloroform liquid—liquid extraction system. The blank of the method is ca. 0.15 nmol 1−1 and the relative standard deviation for duplicate analyses of coastal sea water is 8%.