Electronic Structure Calculations of Monolayer–Protected Gold NanoClusters to Aid Spectroscopic Analysis

The underlying goal of this thesis dissertation is to simulate small monolayer protected clusters (MPCs) via quantum mechanics and molecular mechanics calculations to derive electronic, structural, and dynamical properties. First we specifically focus on monolayers consisting of thiolated oligopeptides and alkanethiols. We construct MPCs with a layer of oligopeptides consisting of α-aminoisobutyric acid units. We use Monte Carlo simulations to determine peptide arrangements and folding. We then perform NMR chemical shifts calculations and compare to experimental measurements to validate the predicted structure. The native -1 oxidation state can be oxidized into 0 and to +1 charge states. The neutral charge state is paramagnetic and behaves quite differently than the anion as manifested by the NMR spectra. The objective is to calculate NMR chemical shits, compare to experiment, and obtain insight into the electronic origin of these shifts. We also use DFT to simulate ENDOR spectra. Finally, we investigate the frontier molecular orbital arrangement in different charge states and determine the HOMO – LUMO energy gap and identify its fingerprint in the optical absorption spectra.