The detection of metal cations is a field of continuing interest, due to their pervasive presence and association with severe health and environmental risks. Transition metal ions such as zinc(II), iron(II), and copper(II) are found in trace amounts in the human body, and they are essential to many biological functions. However, despite their vital biological roles, it is thought that changes in the homeostatic control of these transition metal ions play a key role in the progression of neurodegenerative diseases. The development of molecular probes capable of selectively targeting and scavenging transition metal ions in biological environments could potentially be used to further investigate the role of transition metals in the progression of neurodegenerative diseases. Coumarin-enamine probes have been previously utilized in the Wallace Research Group in the development of multivariate approach to selectively detect divalent metal ions. 7-(diethylamino)-4-hydroxycoumarin was synthesized following the procedures pre-established in the Wallace Research Group and in the literature. Cu (I)-catalyzed azide-alkyne cycloaddition was then used to yield a triazole group to improve the selectivity of the previously synthesized molecular probe for zinc(II) ions. The molecular probe was then fully characterized using NMR and ESI-MS. Fluorescence spectroscopy was used to investigate the optical properties of the coumarin molecular probes in the presence of various metal cations and their counter ions (perchlorate, acetate, and chloride salts). The screening of the metal salts showed that the molecular probe undergoes significant optical changes with two metal cations, copper(II) and zinc(II). In the presence of copper(II), the fluorescence emission is quenched by the copper(II) ions, whereas the fluorescence signal in the presence of zinc(II) increases and is also blue shifted. Competition studies were then performed to determine if other metal cations interfered with the binding of copper(II) and zinc(II) to the molecular probe. The quenching of the fluorescence signal in the presence of copper(II) was observed in the presence of the series of metal cations. Zinc(II) showed the previously observed response in the presence of some metal cations and not others. The results of the competition studies suggest that the presence of other metal cations interferes with the binding of zinc(II) but does not interfere with copper(II) binding.

Development of a coumarin based molecular probe for trace metal ions

255th National Meeting (2018)

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