Natalie M. Rowley

Synthesis, electrochemistry and spectroelectrochemistry of a porphyrin-viologen donor-acceptor diad

A new donor–acceptor (D–A) molecule, 5,10,15,20-[N-benzyl-N′-(4-benzyl-4,4′-bipyridinium-4-pyridyl)]triphenylporphyrin tris(hexafluorophosphate), 4, has been synthesised. The diad, 4, and its precursors, have been fully characterised by 1H and 13C NMR spectroscopy, mass spectrometry, UV/Visible spectroscopy and cyclic voltammetry. In-situ UV/Visible and EPR measurements show that the site of the first electrochemical reduction is the benzylviologen component of the molecule. The second reduction wave from cyclic voltammetry was shown by in-situ EPR to comprise two unresolved one-electron processes, and this was confirmed by chronocoulometry. The first of these two reduction processes rendered the diad diamagnetic, as was shown by the disappearance of the signal due to the benzylviologen radical. The second gave rise to the appearance of a new EPR signal, which was found to correspond to the porphyrin radical. We believe this to be the first reported resolved spectrum of a monoreduced porphyrin radical.

Synthesis, electrochemistry, and spectroelectrochemistry of a metalloporphyrin–viologen donor–acceptor diad

A new donor–acceptor (D–A) molecule, zinc 5-{N-[4-(1′-benzyl-4,4′-bipyridinium-1-ylmethyl)benzyl]-4-pyridinio}-10,15,20-triphenylporphyrinate tris(hexafluorophosphate) has been synthesized. The diad and its precursors have fully been characterised by 1H and 13C NMR spectroscopy, mass spectrometry, UV/Visible spectroscopy and cyclic voltammetry. In situ UV/Visible and EPR measurements show that the site of the first and second electrochemical reductions is the benzyl viologen component of the molecule, whilst the third electron reduction process is associated with the porphyrin moiety. The first reduction process gave rise to an EPR signal due to the benzyl viologen radical, whilst the second caused the molecule to become diamagnetic. The third of these processes gave rise to a new EPR signal, which was found to correspond to the metalloporphyrin radical.

Intramolecular electron transfer in peripherally metallated tetraphenyl porphyrin derivatives containing molybdenum mononitrosyl redox centres

Picosecond laser spectroscopy measurements on the novel complexes [Mo(NO)(L)Cl(Etpp)][Etpp = 5-(E-substituted phenyl-10,15,20-triphenylporphyrin; L = hydrotris(3,5-dimethylpyrazol-1-yl)borate, E =para-O, meta-O, ortho-O; para-NH] indicate that the observed fluorescence quenching in these compounds is due to fast (τ < 30 ps) intramolecular charge separation to produce transient species with lifetimes in the range 120–290 ps.