Michel Le Baccon

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.

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.

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.

New side-bridged bismacrocycles and cross-bridged macrotricycles. Syntheses and Cu(II) complexation study

Eight new cyclen based constrained macropolycycles (4a–4d, 5a–5d) have been obtained by reductive ring cleavage of polyaminal derivatives of bis-macrocycles or macrotricyclic polyammonium salts by sodium borohydride. The mononuclear and dinuclear Cu(II) complexes of these macropolycyclic ligands were isolated as solids and investigated by UV-Vis and EPR spectroscopies. The possibility to obtain the specific formation of mononuclear complexes constitutes an original feature of these new macropolycycles.

Nickel(II) complexes of cyclen- and cyclam-pyridine: topological reorganisations induced by electron transfer

The NiII complexes of cyclen- and cyclam-pyridine (respectively 1-pyridin-2-ylmethyl-1,4,7,10-tetraazacyclododecane and 1-pyridin-2-ylmethyl-1,4,8,11-tetraazacyclotetradecane denoted [NiIIL1]2+ and [NiIIL2]2+) have been isolated and characterised by X-ray diffraction, UV-visible spectroscopy and electrochemical studies for the [NiIIL2]2+ complex. In particular, the [NiIIL2]2+ complex adopts two distinct and stable geometries (type I and V), which mainly differ by the macrocycle configuration. In solution, the isomerisation process between these two configurations is driven by the nickel-centered electron transfer.

Phenylglyoxal for polyamines modification and cyclam synthesis

Abstract The bis-aminals obtained by tetraamine and phenylglyoxal condensation display various behaviours such as equilibrium between different configurations, rearrangements that lead to lactam derivatives, or amine deprotection. Our investigations about them were focused on three different linear amines, and then extended to polyazacycloalkanes cyclen and cyclam. Cyclam was also synthesised with the bis-aminals issued from condensation of linear polyamines with phenylglyoxal. The lactam derivatives described here were moreover, employed for the mono-N-functionalisation of tetraamines by phenyl-acetic acid group.

Cyclen based bis-macrocyclic ligands as phosphates receptors. A potentiometric and NMR study

The host-guest interaction between orthophosphate, pyrophosphate and triphosphate anions and four cyclen based bis-macrocycles ligands possessing ortho-(BOC), meta-(BMC), para-xylenyl (BPC) or 2,6-pyridinyl (BPyC) linker was investigated by potentiometric measurements and NMR spectroscopy. Each ligand gave protonated species in aqueous solution that further formed ternary complexes after binding with anions; these complexes were analyzed as a result of hydrogen bond formation and Coulombic attraction between the organic host and the inorganic guest. The equilibrium constants for all the detected species are reported and the selectivity, illustrated with species distribution diagrams, is discussed. The results unambiguously showed the importance of the distance between the two cyclen cores and underlined, especially for the triphosphate species, the contribution of the nitrogen atom of the pyridinyl spacer as a supplementary anchoring point in acidic medium.

Self-assembly route from a bis-aminal derivative to a new cyclam based macropentacycle

A new powerful two-step synthesis of a cyclam-based macropentacycle ligand is reported. In this procedure, the starting material is the bis-aminal derived from the condensation of cyclam with glyoxal. The tetrameric polyammonium intermediate issued from the self-assembly process and the free ligand were fully characterized by conventional methods and a tetranuclear Cu(II) complex was prepared.

Complexation of the triphosphate anion: tuning the structure of cyclen based macrotricycles with 1,3-dimethylbenzene and 2,6-dimethylpyridine linkers. A potentiometric and NMR study

The host-guest interaction between orthophosphate, pyrophosphate and triphosphate anions and three cyclen-based macrotricyclic ligands was investigated by potentiometric measurements and NMR spectroscopy. The ligands differ from one another by the nature of their spacers, which are 1,3-dimethylbenzene (TMC), 2,6-dimethylpyridine (TPyC) or a combination of the two (TMPyC). In aqueous solution, each ligand gave protonated species that further formed ternary complexes after binding with anions; these complexes were analyzed as a result of hydrogen bond formation and coulombic attraction between the organic host and the inorganic guest. The equilibrium constants found for all the detected species are reported and the selectivity, illustrated with species distribution diagrams, is discussed. The results unambiguously showed that the ligand possessing a single supplementary anchoring site (the pyridinyl spacer) exhibited the greatest affinity for the phosphate species in a large p[H] range.

Basicity and coordination ability of linear hexa-amines in relation to N-(CH2)n-N chain-link lengths. A solution study

Abstract The synthesis of the two new linear hexa-amines, 3,7,10,14-tetraazahexadecane-l,16-diamine (L 1 ) and 5,9,12,16-tetraazaicosane-l,20-diamine (L 2 ) has been reported. Ligand protonation and Cu(II) and Zn(II) coordination have been studied in aqueous solution by means of potentiometric, microcalorimetric (298.1 K, I =0.1 mol dm −3 ) and spectrophotometric (UV–Vis, 1 H and 13 C NMR) measurements. The species present in solution and their stability constants have been determined. L 1 forms mono- and binuclear complexes in aqueous solution with Cu(II). In the [ML 1 ] 2+ complexes, the metal ion is coordinated by five nitrogen atoms, while in the [ML 2 ] 2+ complexes the metal ion is four-coordinate. This different behavior is explained in terms of the different numbers of methylene groups between adjacent nitrogen atoms.