title: Electronic and vibrational properties of meso-tetraphenylporphyrin on silver substrates.
abstract: The electronic and vibrational properties of meso-tetraphenylporphyrin (mtpp) on silver substrates are investigated using UV-vis and surface-enhanced resonance Raman scattering (SERRS) spectroscopy. Whereas the vibrational signatures associated with the tetrapyrrole backbone exhibit minor variations throughout sequences of consecutively recorded SERRS spectra, the C═C stretching vibrational modes localized on the meso-phenyl moieties of mtpp exhibit noticeable intensity fluctuations, masked in the average SERRS response. We attribute the observed vibrational-state-specific blinking events to conformational changes in mtpp, namely, torsional flexibility which mediates the coupling between the π-framework of the meso-phenyls and the underlying metal substrate.
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States.
authors.forename: Patrick Z
authors.initials: PZ
authors.lastname: El-Khoury
authors.forename: Karoliina
authors.initials: K
authors.lastname: Honkala
authors.forename: Wayne P
authors.initials: WP
authors.lastname: Hess