Complexation of Sc3N@C-80 Endohedral Fullerene with Cyclic Zn-Bisporphyrins: Solid State and Solution Studies

作者：Hernandez Eguia Laura P; Escudero Adan Eduardo C; Pinzon Julio R; Echegoyen Luis^*; Ballester Pablo

来源：Journal of Organic Chemistry, 2011, 76(9): 3258-3265.

DOI：10.1021/jo200154d

We report the synthesis of two cyclic beta-pyrrole unsubstituted meso-tetraphenyl bisporphyrins in which the porphyrin units are connected by two 2,3-hexadiynyl-1,6-dioxo or two hexy1-1,6-dioxo spacers, respectively. Both cyclic porphyrin dimers exist in solution as mixtures of two conformational isomers. In the solid state, the receptor with diynyl spacers forms a 1:1 complex with the icosahedral (I-h) isomer of the trimetallic nitride endohedral fullerene Sc3N@C-80. In this complex the receptor adopts a scoop-shaped conformation having a dihedral angle of 87.25 degrees between the two porphyrin planes. The hexyl spaced analogue, however, adopts a similar conformation upon encapsulation of one molecule of Sc3N@C-80 in a self-assembled dimeric capsule. The capsular complexes pack in columns and render the fullerene units completely isolated. In toluene solution, H-1 NMR experiments indicate that the endohedral fullerene Sc3N@C-80 is exclusively bound by the expanded isomer of both dimers. UV-vis and fluorescence titration experiments confirmed the existence of strong pi-pi interactions between the fullerene Sc3N@C-80 and the flexible bisporphyrin dimer with hexyl spacers. At micromolar concentration, the flexible receptor forms only a 1:1 complex with the endohedral fullerene with stability constant value of K-a = 2.6 +/- 0.3 x 10(5) M-1.

• 出版日期2011-5-6