Dibenzofuran spacer. Pacman

Rosenthal J, Nocera DG (2007) Oxygen activation chemistry of pacman and hangman porphyrin architectures based on xanthene and dibenzofuran spacers. Prog Inorg Chem 55 483-544... 

Oxygen Activation Chemistry of Pacman and Hangman Porphyrin Architectures Based on Xanthene and Dibenzofuran Spacers... 

Pacman architectures (Section IV). This proposed oxidative pathway, which is shown in Fig. 21, however, can be circumvented by the formation of the highly stable diiron(III)- 4-oxo bisporphyrin Pacman via loss of H2O. One motivation for the preparation of the DPD framework was the hope that installation of the splayed, rigid spacer would hinder intramolecular p-oxo formation due to the torsional strain associated with clamping down the Pacman bite angle. However, as Fig. 22 shows, the dibenzofuran to be a surprising flexible unit. Somewhat... 

In most cases, the nature of the spacer is the governing factor as far as optical properties are concerned. Pacman porphyrins, with rigid spacers such as anthracene and biphenylene, have received much attention due to the electro-catalytic properties of their cobalt complexes. Variations of both the dihedral angle and the distance between the porphyrm rings in these architectures have afforded examples of cofacial porphyrins linked by xanthene and dibenzofurane derivatives. Recent examples are detailed hereafter. 

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