1,4,7-Triazacyclononane ligand structure

A series of structurally characterized di-yttrium(III) complexes bearing alkoxy-derivatized triazacyclononane ligands have been examined as initiators for lactone ROP.886 Both (296) and (297) are active for the polymerization of rac-LA at RT, but little control is afforded over molecular weights. Chain length distributions are broad, (Mw/Mn= 1.5-2.2) and attempts to identify the initiating group via end-group analysis have not been successful. 

A new imidazole-functionalized calix[4]arene ligand, able to form a dinuclear Cu2+ complex, has been reported to hydrolyze HPNP and ethyl p-nitropheny lphosphate [70]. The dinuclear complex was found to be 22-and 330-fold more reactive than the corresponding monomer towards the above substrates, respectively. Dinuclear Cu2+ complexes of linked triazacyclononane ligands are reported to promote the hydrolysis of the monoribonucleotide GpppG, a model for the 5 -cap structure of mRNA [71]. The dinuclear complexes offer some 100-fold higher reactivity compared to the mononuclear Cu2+-triazacyclononane system. 

In 1996, an optimization of the oxidation protocol was described by De Vos and Bein who found a dependence of catalytic activity on temperature, solvent, and ligand structure . Their investigations showed that different substituents on the nitrogen atoms of the triazacyclononane ligands 168 have a great effect on the activity... 

Tei, L., Baum, G., Blake, A.J., Fenske, D., and Schrooder, M. Lanthanide complexes of a new nonadentate ligand derived from 1,4,7-triazacyclononane synthesis, structural characterisation and NMR spectroscopic studies,/. Chem. Soc., Dalton Trans. (2000), 2793-2799. 

The 0-0 bond in side-on dicopper-dioxygen complexes can be easily cleaved, affording dicopper(III) bis-p-oxo diamond core-type structures.40,85,106 The first crystallographically crystallized complex of this type, described by Tolman and coworkers, contained /V-alkylated triazacyclononane ligands.106 Subsequently, a large number of bis-p-oxo dicopper(ffl) intermediates were observed in various chemical systems.97 In many cases, dicopper(II) X-T 2 T 2 peroxo species and dicopper... 

Pendent arm 1,4,7-triazacyclononane macrocycles (91) and (92) have been used to stabilize the zinc-to-phenoxyl bond allowing characterization of these compounds.477 The interest in the zinc complexes comes from the wide potential range in which it is redox stable allowing observation of the ligand-based redox processes, this allows study of the radical by EPR and the electronic spectra is unperturbed by d-d transitions. Macrocycles of the type l,4,7-tris(2-hydroxybenzyl)-1,4,7-triazacylononane form a bound phenoxyl radical in a reversible one-electron oxidation of the ligand. The EPR, resonance Raman, electronic spectra, and crystal structure of the phenoxide complexes were reported. This compound can be compared to a zinc complex with a non-coordinated phenoxyl radical as a pendent from the ligand.735... 

A,A A"-tris[(2S)-2-hydroxypropyl]-1,4,7-triazacyclononane (LH3) forms the air-stable mangane-se(II) species [MnLH3][MnCl4] when conditions are such that the ligand remains fully protonated. The X-ray structure indicates the presence of a trigonal prismatic coordination geometry." ... 

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