Porphyrin dimers linked by conjugated butadiynes

Article abstract of DOI:10.1016/S0040-4020(01)89451-5

1,3-Butadiynes R---C≡C---C≡C---R, where R = 5′-substituted nickel(II) octaethylporphyrin (NiOEP) (1e), 2′-substituted nickel(II) 5′, 10′, 15′, 20′-tetraphenylporphyrin (NiTPP) (4e), and 2′-substituted nickel(II) heptaethylporphyrin (NiHEP) (5d), have been prepared from the respective bromovinyl species by dehydrobromination and oxidative coupling. The published synthesis of (1e) has been improved to achieve a 40% yield for four steps from NiOEP. The metal-free bis(OEP) diyne was prepared by acid treatment of (1e), while more strenuous conditions led to a novel furan substituted at the 2- and 5-positions with OEP units. The visible absorption spectra of the 5′- and 2′-substituted diynes differ markedly, the former compounds exhibiting split absorption bands and red shifts indicative of extensive chromophore interaction.