Structural and Chemical Properties of CF₃ Substituted Corrole and Relative Complexes

Corrole and sapphyrin with the smallest meso-substituents reported so far were prepared in a one-pot synthesis that relies on a non-aldehydic precursor for introducing CF₃ groups. The substantial amounts of products obtained by this facile pathway allowed for the full characterization of 5,10,15-tris(trifluoromethyl)corrole (TFC), the access to a variety of stable chelates thereof and investigations that disclose the unique structural and chemical properties induced by the CF₃ substituents. Cyclic voltammetry examinations of 5,10,15-tris(trifluoromethyl)correlate cobalt, gallium and phosphorus were performed for uncovering the electronic effect of the meso-CF₃ groups, particularly relative to that of meso-C₆F₅ groups. Under identical conditions, the redox potentials of the M(TFC) complexes were found to be positively shifted by 130-220 mV relative to the analogous M(TPFC) (5,10,15-tris(pentafluorophenyl)correlate complexes) complexes (M = Co, Ga, P).^[1] Hints for the stronger electron withdrawing effect imposed onto the coordinated metal ion by the CF₃ vs. C₆F₅ meso-substituents are given by comparison of both crystallographic data and Lewis acidity. A weaker fluorescence quantum yield of P(TFC) vs. P(TPFC)^[2] was observed, which most likely attributable to the absence of the meso-aryl groups and the structural differences of planarity. The novel 5,10,15,20-tetra(trifluoromethyl)sapphyrin does undergo only single protonation proven by titration monitored by NMR and UV-vis spectroscopies, which according to its crystal structure is stabilized by favorable non-bonding F/H interaction between the meso-CF₃ and the inverted pyrrolic NH.

Reference:

[1] Q. Chen, M. Soll, A. Mizrahi, I. Saltsman, N. Fridman, M. Saphier, Z. Gross, Angew. Chem. Int. Ed. 10.1002/anie.201710106

[2] J. Vestfrid, R. Kothari, A. Kostenko, I. Goldberg, B. Tumanskii, Z. Gross, Inorg. Chem. 2016, 55, 6061-6067.