Post-Installation of Fused Benzoheptagons at the Periphery of NiII Porphyrins: Helical Structures and Conformation-Adjustable Fullerenes Binding

Abstract

Fused-benzoheptagon-installed Ni^II porphyrins were synthesized by a protocol consisting of (2-formyl)arylation at the meso-position(s) of Ni^II porphyrins, conversion of formyl group to methoxyethene group by Wittig reaction, and final Bi(OTf)₃ -catalyzed cyclization. The structures of these porphyrins have been revealed by X-ray analysis. Owing to the installed heptagon ring(s), these porphyrins show curved structures with conformational flexibility. Dimer has been shown to have a small activation barrier for inversion and to capture C₆₀ and C₇₀ with large association constants with adjustable conformational changes.

Keywords: adjustable conformation; benzoheptagons; fullerene host; fused porphyrins; helicene.