CHEMISTRY: Porphyrin Mandibles

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Science  10 Nov 2000:
Vol. 290, Issue 5494, pp. 1055b
DOI: 10.1126/science.290.5494.1055b

The ability to craft molecular shape has allowed chemists (with some help from porphyrin groups) to manipulate attractive interactions between molecules and repulsive interactions within a molecule. Sun et al. have created a small, jaw-like trap for fullerenes in which two substituted porphyrins are linked by a Pd center. The biting, while tight, is noncovalent and labile—bound C60 can be displaced by C70. Bell et al. have studied conformational changes that occur after photoinduced charge transfer in large U-shaped molecules bearing porphyrin and methyl viologen end groups. Initially, in one isomer of the molecule, the porphyrin group, which is neutral, lies near the methyl viologen group, which has a double positive charge. Transfer of an electron appears to occur through space and creates two end groups, each with a single positive charge, that strongly repel and open the molecular jaws. The long lifetimes of the charge transfer complex (hundreds of nanoseconds) suggest the electron is forced to return the long way, through the molecule. — PDS

J. Am. Chem. Soc. 122, 10704; 10661 (2000).

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