Luminactive Gold Complexes: Synthesis and Photophysics

Case Western Reserve University, Cleveland OH

Investigators

Abstract

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Thomas G. Gray at Case Western Reserve University that emphasizes the organometallic chemistry and excited-state properties of gold(I). The leading objective is emplacement of gold(I) centers onto fluorescent organic molecules. The heavy-atom effect of gold opens access to the fluorophores' triplet-state photochemistry and photophysics. Gold can be introduced in sensitive, conjugated molecules that absorb at preordained wavelengths. Two new synthetic methods are demonstrated where gold(I) fragments are attached to aromatic skeletons through carbon-gold sigma bonds. The first of these, base-promoted transmetallation, binds gold to the peripheries of aromatic molecules and is broadly general and functionally tolerant. The second is a [3 + 2] cycloaddition reaction of gold(I) azides with terminal alkynes that yields gold(I) triazolato moieties. Photophysical studies, which include static and time- resolved emission measurements, demonstrate triplet-state luminescence from aromatics functionalized with gold. The synthesis concepts that underlie these activities permit measurement of both internal heavy-atom effects (through direct carbon-gold attachment) and of external effects, where gold is suspended above an emitting moiety upon a photoinert spacer. A variety of day-to-day applications call for materials that are robust, tunable triplet-state emitters. Among these are light-emitting diode technology, photosensitization, and biological labeling. This research will also contribute to chemical pedagogy through the development of an undergraduate laboratory exercise in the synthesis and characterization of group 11 complexes of azadipyrromethene chromophores. This research is also training undergraduate and graduate students for scientific careers in industry, government, the military, and academia.