RUI: Highly Luminescent Multinuclear Coinage Metal Arrays with a Twist: A New Approach to Design Light-Emitting Molecular Wires and Coils

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The Chemical Synthesis Program of the Chemistry Division supports the project by Professor Michael Stollenz, a faculty member in the Department of Chemistry and Biochemistry at Kennesaw State University. The Stollenz Group is exploring novel molecules that contain specific arrangements of individual metal atoms. The molecules are highly luminescent, and they have the potential to serve as molecular wires. Molecular wires have fascinated scientists for decades because they are an essential component of building miniaturized electron devices on the submicroscopic scale. Luminescent, multinuclear complexes of copper, silver, and gold are of particular interest in this regard, since they can also be applied in molecular/organic light-emitting diodes (OLEDs). To build molecular wires of this nature, synthetic methodologies are needed that can produce new molecules that contain specific arrangements of the individual metal atoms. With this in mind, Professor Stollenz and his group are working to develop new methodology for producing not only strictly linear arrays of copper, silver, and gold ions, but also arrangements that are substantially bent for use in conducting molecular coils. A long-term prospect for such molecular coils, embedded in electronic circuits, is to utilize them as tiny electromagnets that can be integrated in nanomachines and other nanoscaled electronic devices. Such devices can in turn be applied in nanorobots that deliver drugs inside a human body. If these devices are luminescent, their path can be followed by fluorescence imaging. The Broader Impacts of the work also includes the mentoring and training of undergraduate and master students from the significant population of underrepresented groups at Kennesaw State University.This research program focuses on the development and implementation of new strategies to multinuclear coinage metal arrays that both serve as potentially conducting molecular coils and as molecular/organic light-emitting diodes (OLEDs). The underlying synthetic methods give a fundamental approach to control aggregation of linear cluster assemblies and provide a deep insight into the coordination chemistry of multinuclear complex arrays in general. Specifically, a library of new bis(amidine) ligands that are capable of accommodating at least four copper or silver centers, arranged in a linear fashion, is being created. The incorporation of Cu(I) ions in the arrays is accomplished by employing a clean organometallic Cu(I) source, mesitylcopper. The resulting linear cluster assemblies can either be homoleptic complexes or complexes that retain the mesityl groups. Bis(amidine) ligands with additional terminal N-donor groups are selectively protected by AuCl complex fragments. These heretofore unknown digold-metalloligands are utilized as building blocks for new linear or bundled homonuclear gold or heterobimetallic gold/copper cluster assemblies as promising luminescent materials. Finally, new bis(amidinato)lithium complexes are synthesized and their behavior in solution is investigated. Furthermore, this program provides an in-depth training and mentoring of undergraduate and graduate students in synthesis, characterization techniques (crystallography and spectroscopy), oral presentation skills, scientific writing, laboratory safety, and data management. These measures prepare students to achieve their ambitious career goals in science or industry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.