Single Molecule Conductance Spectroscopy to Probe Aurophilicity and Catalysis of Dinuclear Gold Complexes

Trustees Of Boston University, Boston

Investigators

Abstract

In this NSF project, funded by the Chemical Mechanism, Function, and Properties Program of the Chemistry Division, Professor Eric Cueny of the Department of Chemistry and Professor Maria Kamenetska of the Departments of Chemistry and Physics at Boston University are using single molecule conductance measurements via the scanning tunneling microscope break junction (STMBJ) technique to evaluate the strength of interactions between gold ions within molecules, known as aurophilicity. Molecules containing two gold ions, dinuclear gold complexes, often act as catalysts for reactions necessary to produce societally important products or as light sources. While, aurophilicity between the gold ions in the molecule is commonly invoked as the key factor in the catalytic and luminescent properties of dinuclear gold complexes, a general method for quantifying aurophilic interactions is lacking. Here the research team at Boston University propose to develop a much-needed, general experimental technique for studying factors that promote aurophilicity. The ultimate goal is to establish the chemical principles for strengthening aurophilic interactions in dinuclear gold complexes in order to engineer more effective gold complexes as photocatalysts. Dinuclear gold complexes bearing a variety of ligands have been synthesized and studied for catalytic and luminescent applications. The aurophilic interactions in these dinuclear gold complexes are credited for the desirable catalytic and luminescent properties. While computations have been used to evaluate aurophilicity, direct experimental measurements of aurophilic interactions are lacking. Resonance Raman spectroscopy has been used in the direct quantification of such aurophilic interactions; however, this measurement requires Raman silent ligands precluding a more general analysis of aurophilic interactions. By measuring the conductance of dinuclear gold complexes in an STMBJ, the research team can correlate the conductance with the strength of aurophilic interactions. In this proposal they will 1) establish single molecule conductance signatures of aurophilic interactions 2) use single molecule conductance measurements to quantify aurophilicity in dinuclear gold complexes and 3) use single molecule conductance to probe the aurophilicity and reactivity of dinuclear gold complexes under homocoupling reaction conditions. Ultimately, they aim to establish the chemical principles behind strengthening aurophilic interactions. Guided by these principles, the research team seek to improve the photochemical activity of these dinuclear gold complexes. 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.