Copper(II), iron(III) and cobalt(III) complexes of the pendent-arm cyclam derivative 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane

Compounds of amine-substituted cyclic amines: synthesis and structures

Cyclic tetra-amines with amine substituents on the central carbon atom of C3 ring segments are readily prepared by reduction of nitro-substituted aza-macrocycles, formed by reactions of metal-ion amine compounds with formaldehyde and a nitro-alkane. Reactions of bis-(ethane-1,2-diamine)-copper(ii) or -nickel(ii) cations with formaldehyde and nitroethane form the trans (anti) and cis (syn) isomers of (6,13-dimethyl-6,13-di-nitro-1,4,8,11-tetra-azacyclotetradecane)-copper(ii) or -nickel(ii)) cations, which are readily reduced to form the trans and cis-6,13-diamino cations, from which the trans- and cis-amine substituted cyclic tetra-amines can be isolated. Similar reactions for the (3,7-diaza-nonane-1,9-diamine)-copper(ii) or -nickel(ii) cations lead to 6-methyl-1,4,8,11-tetra-azacyclotetradecane-6-amine. Amine-substituted cyclic tetra-amines with different ring sizes or alkyl substituents can similarly be prepared by using different diamines or alkyl-nitro compounds. This review is primarily about compounds formed by trans-6,13-diamino and 6-amino-1,4,8,11-tetraazacyclotetradecanes with d-transition-metal ions. The amines react with transition-metal ions in much the same manner as 1,4,8,11-tetraazacyclotetradecane (cyclam), forming compounds with isomeric configurations arising from the four chiral nitrogen centres of coordinated cyclam, the cis- or trans-configurations of the amine substituents and a form of geometrical isomerism arising from the relationship between the chiral coordinated cyclam configuration and the orientation of the substituents. The amine-substituted cyclams coordinate by the four cyclam nitrogen atoms, in planar or folded arrangements, and also by one or both of the amine substituents. Non-coordinated amine substituents can be protonated. The amine substituents can be modified by methylation, amide formation and reaction with aldehydes to form imines. The imines formed with functionalised aldehydes can be reduced to form variously functionalised secondary amine substituents. This all leads to complex coordination chemistry and X-ray crystallographic structure determinations have been critical in understanding the configurations present. Structures in the Cambridge Crystallographic Data Base of all relevant compounds are listed.

Metal induced folding: synthesis and conformational analysis of the lanthanide complexes of two 44-membered hydrazone macrocycles

Six new lanthanide complexes of two 44-membered macrocycles have been prepared and characterised in solution. An analysis of the conformations of the free macrocycles and their lanthanide complexes both in solution (2D NMR) and in solid state (X-ray crystallography) demonstrate that the complexation induces changes in folding of the macrocycles.

Pendent Nucleophiles on Coordination Complexes: Hydrogen-Bond Donor and Acceptor Ability

Analysis of the crystal structures of a variety of transition metal complexes in which the ligands are hypodentate, thus providing pendent ammonio, amino, and/or hydroxy groups, has been conducted with the objective of defining the labile interactions of these pendent groups. In the case of pendent ammonio groups, not only do they appear to be good H-bond donors but they are frequently involved in contacts suggestive of hyperdenticity at N. For pendent amino and hydroxy groups, of particular interest in regard to their potential activity as nucleophiles, their H-bond acceptor ability frequently seems to be rather limited and it is unclear whether it can be related to either the nature or the charge on the bound metal cation.