Tetraazamacrocycles, cyclic molecules with four nitrogen atoms, have long been known to produce highly stable transition metal complexes. Cross-bridging such molecules with 2-carbon chains has been shown to enhance the stability of these complexes even further, providing enough stability to use the resulting compounds in applications as diverse and demanding as aqueous, green oxidation catalysis all the way to drug molecules injected into humans. Although the stability of these compounds is believed to result from the increased rigidity and topological complexity imparted by the cross-bridge, there is insufficient experimental data to exclude other causes. In this study, standard organic and inorganic synthetic methods were used to produce unbridged dibenzyl tetraazamacrocycle analogues of known cross-bridged tetraazamacrocycles and their transition metal complexes to allow direct comparison of molecules identical except for the cross-bridge. The syntheses of the known tetraazamacrocycles and the novel transition metal complexes were successful with high yields and purity. Initial chemical characterization of the complexes by UV-Visible spectroscopy and cyclic voltammetry shows little difference in electronic properties from bridged versions. Direct comparison studies of the unbridged and bridged compounds’ stabilities remain to be carried out and will shed light on the importance of the cross-bridge to complex robustness.
Walker, Ashlie N.; Ayala, Megan A.; Bergagnini, Mackenzie C.; Bui, P. John D.; Chidester, Stephanie N.; Doeden, Chad I.; Sweany, Louise; and Hubin, Tim
"Transition Metal Complexes of Dibenzyl Tetraazamacrocycles,"
SWOSU Journal of Undergraduate Research:
Vol. 1, Article 2.
Available at: http://dc.swosu.edu/jur/vol1/iss1/2