Remarkably bent, ethane-linked, diiron(III) mu-oxobisporphyrin: synthesis, structure, conformational switching, and photocatalytic oxidation.

A remarkably bent diiron(III) mu-oxobisporphyrin containing a highly flexible ethane linker is reported that authenticates, for the first time, the unprecedented ability of this platform to "open" and "close" its binding pockets, leading to facile syn-anti conformational switching with very high vertical flexibility of over 6.5 A in a single molecular framework. X-ray structural characterization reveals the bent diiron(III) mu-oxobisporphyrins with the smallest known Fe-O-Fe angles of 147.9(1) degrees for any iron(III) mu-oxo porphyrin dimers reported so far. Two rings in a molecule are not slipped but are face to face in a nearly eclipsed geometry and are placed so close that at least six carbon atoms from each of the macrocycles are driven to be essentially less than the van der Waals contacts (<3.4 A). The complex catalyzes the rapid photoinduced oxygenation of phosphites under mild conditions using aerial oxygen.