A large porphyrin analogue, cyclopyridinepyrrole, containing no meso bridging atoms, has been synthesized through Suzuki coupling. In its neutral form, this macrocycle exists as a mixture of two figure-eight conformers that undergo fast exchange in less polar solvents. Upon protonation, the dynamic twist can be transformed into species that adopt a ruffled planar structure or a figure-eight shape depending on the extent of protonation and counteranions. Conversion to a bisboron difluoride complex via deprotonation with NaH and treatment with BF3 acts to lock the macrocycle into a figure-eight conformation. The various forms of cyclopyridinepyrrole are characterized by distinct NMR, X-ray crystallographic, and spectroscopic features.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry