Electronic Influences of Functional Modifications on Tetra-Aza Copper (II) Complexes

Abstract

A library of novel pyridinophane tetra-aza macrocyclic molecules derived from 1,4,7,10- tetraaza-2,6-pyridinophane (pyclen) capable of chelating biologically relevant metal ions has been synthesized. Applications of these types of molecules currently being pursued are 1) therapeutic, focusing on radical scavenging and metal chelation and 2) diagnostic, focusing on magnetic resonance imaging (MRI) contrast agents when complexed with specific metal ions. Despite wide interest in these molecules, a full study of the electronic effects imparted by substitution to the pyridyl moiety and the subsequent impact on the metal center has not yet been conducted. The objective of the present study is to characterize metal complexes of four, new tetra-aza macrocyclic metal chelating molecules. The pyridyl functional groups studied include: unmodified pyridyl (L1), 14-hydroxyl (L2), 14-nitrile (L3), and 14-chloro (L4) modified pyclen structures. Procedures for metal ion chelation with copper (II) ion, followed by characterization and analysis of the electronic environments of each are presented.