Jozef Hodyl PhD Thesis - Theses - Flinders University

amide oxygen atoms on the pendant arms, with the metal ion situated between thetwo planes. In all cases this causes the pendant arms to juxtapose away from thecyclen skeleton in a pseudoaxial conformation. 122The outward projection of the pendant arms in 22 suggests that if the pendantarms were increased in length, or broadened, or both, a partially or fully enclosedcavity could result. Hence, the arrival of studies concerned with producing afunctionalised cavity. Cadmium(II) complexes 23 to 26 were all prepared fromligands obtained by reacting cyclen with an appropriate epoxide: ethylene oxide for23, (S)-propylene oxide for 24, (S)-styrene oxide for 25 and (2S)-(+)-3-phenoxy-1,2-epoxypropane for 26. Quantitative yields are common when functionalising cyclen inthis way, as is the formation of the complex as its diperchlorate salt.23 2425 26The size of the cavity above the O 4 plane in these receptor complexes may varyfrom negligible in 23 and 24 to shallow and saucer-shaped in 25 to quite substantialin 26, depending on the length and positioning of the pendant arms. 124 The (S)-propylene oxide appended structure 24 was first synthesised in 1988 by Hancock and21