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Structural and Binding Features of Cofacial Bis‐Porphyrins with Calixarene Spacers: Pac‐Man Porphyrins That Can Chew

2005; Wiley; Volume: 11; Issue: 14 Linguagem: Inglês

10.1002/chem.200401225

1521-3765

Danica Jokic, Corinne Boudon, Grégory Pognon, M. Bonin, Kurt Schenk, Maurice Gross, Jean Weiss,

Magnetism in coordination complexes

Based on the efficient combination of calixarene spacers and acetylenic porphyrin derivatives, a new generation of cofacial bis-porphyrins has been synthesized. The first crystal structure of a cofacial bis-porphyrin-calixarene conjugate is reported. Their unique architectural features, analogous to those of pac-man-type bis-porphyrins, allow these calixarene-porphyrin conjugates to adapt their shape to the size of bidentate guests, such as diazabicyclo[2.2.2]octane (dabco) and 1,4-pyrazine. The predefined, cofacial arrangement of the porphyrin moieties observed in the solid state and in solution results in extremely high affinities (in the range of 10(9) M(-1)) for these guests. The 1,3-alternate calixarene conformations afford "open-mouth" pac-man structures whose ability to bite on nitrogen bidentates depends on their functionalization. A cone conformer provides a much more flexible structure that exhibits the highest affinity for dabco and pyrazine.