Dynamics of Porphyrin Electron‐Transfer Reactions at the Electrode–Electrolyte Interface at the Molecular Level

Porphyrins as Active Components for Electrochemical and Photoelectrochemical Devices

“…37 The slow reductive processes provided an opportunity to get insights into the interfacial reactions and dynamics at the single-molecule level. 128 Indeed both H 2 TPyP and H 2 TCPP give rise to different contrast at the STM in the oxidized (dark spots) H 2 P(0) and reduced (bright spots) H 4 P(-II) forms. In a brilliant experiment the potential was kept at −0.1 V vs. SCE to ensure that the only adsorbed species was the phlorin.…”

Probing Single Flavoprotein Molecules on Graphite in Aqueous Solution with Scanning Tunneling Microscopy

“…For example, Meier et al introduced and described a new route to study local reactivity of nanoparticles using an STM tip electrode as a local sensor, which aided the understanding of the interfacial electron‐transfer (ET) dynamics at the single‐molecule level possible 2. In the past three decades, direct ET between molecules and electrodes has been extensively investigated due to the importance for biomolecular electronics and nanosensing purposes 3–7. ET reactions in enzymes play an important role in biologically vital processes in living cells, most notably in photosynthesis and respiration.…”

Self-assembled monolayers formed by 5,10,15,20-tetra(4-pyridyl)porphyrin and cobalt 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine on iodine-passivated Au(111) as observed using electrochemical scanning tunneling microscopy and cyclic voltammetry

“…The heights of the large peaks near 0.0 V vs. Ag/AgCl show a linear dependence on the scan rate, consistent with an adsorbed species. Adsorbed TPyP is known to undergo reversible two-electron oxidation on Au(1 1 1) in dilute HClO 4 [10,11]. Using our EC-STM images of the porphyrin monolayers (see below) to roughly estimate the surface coverage, we calculate that the two-electron oxidation of a TPyP monolayer should result in a charge transfer of 1.26 Â 10 À7 C/mm 2 .…”

“…Porphyrin SAMs have been investigated extensively using scanning tunneling microscopy (STM) in vacuum and inert liquids [7,8], and the formation of porphyrin SAMs on metal surfaces in electrolyte solutions has also received attention from multiple groups. In particular, Borguet et al have extensively investigated porphyrin SAMs on bare Au(1 1 1) electrodes [9][10][11][12]. Importantly, they found that the electrode potential can be used to control ordering in TPyP monolayers on bare Au(1 1 1).…”