Dibenzidecaphyrins (1.0.0.1.1.1.0.0.1.1) and Their Bis-BF2 Complexes

J Org Chem. 2018 Dec 7;83(23):14277-14285. doi: 10.1021/acs.joc.8b01812. Epub 2018 Nov 15.

Abstract

The largest dibenziporphyrinoids discovered until date, dibenzidecaphyrins (1.0.0.1.1.1.0.0.1.1), were synthesized in 8-10% yields by condensing m-phenylene-based pentapyrrane with pentafluorobenzaldehyde under mild reaction conditions. The crystal structure obtained for one of the decaphyrin macrocycles revealed that the macrocycle adopts a figure eight conformation and showed nonaromatic features. The decaphyrin macrocycles were further characterized by various spectral, electrochemical techniques, and computational studies. The dibenzidecaphyrin macrocycle showed half the number of proton NMR resonances, indicating the high symmetry of the macrocycle. The decaphyrins showed a broad absorption in the 600-900 nm region along with a well-defined band at 448 nm, and the macrocycles were stable under redox conditions. The decaphyrins were treated with BF3·OEt2/triethylamine in CHCl3 at reflux temperature, followed by column chromatography, to afford bis-BF2 complexes of decaphyrin in 34-40% yields. The spectral and DFT studies supported a figure eight conformation for the bis-BF2 complexes, and electrochemical studies indicated that the bis-BF2 complexes were electron deficient compared to the free-base decaphyrin macrocycles.