Showing papers by "George A. Koutsantonis published in 2004"
TL;DR: Structural studies of seven very differently functionalised derivatives of calix[4]arene have been used to provide an analysis of the numerous factors which may influence solvent adduct formation by calixarenes.
Abstract: Structural studies of seven very differently functionalised derivatives of calix[4]arene have been used to provide an analysis of the numerous factors which may influence solvent adduct formation by calixarenes. Evidence is presented that even where a solvent guest is included within the calixarene cavity, interactions solely within the cavity cannot be seen as the sole influences upon the guest position and orientation.
41 citations
TL;DR: In this paper, an asymmetric pendent arm which does not significantly modify the macrocycle conformation has no significant effect upon the geometry of the coordination sphere of a bound metal, where substitution engendering chirality does cause a change in the ligand conformation, in particular for a ligand of restricted stereochemistry.
21 citations
TL;DR: Use of a hydroxyl-functionalized open chain tetramine in a template reaction based on its Cu(II) complex leads, after reduction, to a new tetraaza macrocycle with both amino andhydroxyl substituents.
Abstract: Use of a hydroxyl-functionalized open chain tetramine in a template reaction based on its Cu(II) complex leads, after reduction, to a new tetraaza macrocycle with both amino and hydroxyl substituents. The macrocycle is formed predominantly as its trans (anti) isomer, though the cis form is detectable and both have been structurally characterized in the form of their metal complexes. Although both the Cu(II) and the Co(III) complexes of the tetramine precursor ligand have the hydroxyl group in an axial position of a chair six-membered chelate ring, the trans macrocycle forms Co(III) complexes with this substituent in both equatorial and axial positions.
19 citations
TL;DR: In this paper, a pendent-arm cyclam-like macrocycle was constructed for the reaction between 1,2-diamine and 3,3-dichloropivalic acid.
Abstract: Reaction between ethane-1,2-diamine and 3,3'-dichloropivalic acid results in different, isomeric tetra-amine derivatives, one a tetraamino carboxylic acid and the other a carboxamidotriamino alcohol, depending upon reaction conditions. Intended conversion of the Cu(II) complex of the former to a cyclam-like macrocycle through reaction with nitroethane and formaldehyde results in isolation of derivatives of both the former and the latter. This can be rationalized by assuming the intermediacy of an azetidinone, a species similar to that seen in simpler reactions of dichloropivalates. A single reaction thereby provides pendent-arm macrocycles where one has an electrophilic and the other a nucleophilic substituent. Parallel chemistry is not seen in the reaction between propane-1,3-diamine and 3,3'-dichloropivalate.
18 citations