Isomeric porphyrin phenanthrenequinones: synthesis, NMR spectroscopy, electrochemical properties, and in situ EPR/ENDOR studies of the o-semiquinone anion radicalsElectronic supplementary information (ESI) available: 1H and 13C NMR data for various phenanthrene derivatives. See http://www.rsc.org./suppdata/p2/b1/b110273g/

Abstract

Porphyrin quinones are attractive model compounds for mimicking natural electron transfer processes. While the overwhelming majority of studies have been performed with porphyrin p-quinones the isomeric porphyrin o-quinones have been mostly neglected. Using phenanthrene-9,10-quinones as the acceptor component we have prepared several porphyrin o-quinones (1, 2, 5, 6) and show that a facile and simple variation of ΔGET can be achieved by using the in situ formed semiquinones for metal chelatization. Additionally, detailed NMR studies show that for asymmetrically substituted porphyrins a complete assignment of the 1H- and 13C-chemical shifts is possible. Complete NMR assignments were necessary for an unambiguous structure determination.