Chiral Tetraphenylene-Bridged Carbaporphyrin Dimer

A chiral carbaporphyrin dimer featuring a tetraphenylene bridge was synthesized via Yamamoto-type coupling from an elaborated dibrominated carbaporphyrin monomer precursor. The highly distorted tetraphenylene-bridged carbaporphyrin dimer 1 exhibits axial chirality with a double π-helical structure. Enantiomers R-1 and S-1 were stably resolved using high-performance liquid chromatography (HPLC) on a chiral stationary phase, and the largest absorption dissymmetry factor, |g_abs|, was measured to be 0.024 at 719 nm. Treatment of each resolved enantiomer of 1 with excess copper(II) acetate at reflux afforded the corresponding enantiopure bis-Cu complex (R-1·Cu and S-1·Cu). Metalation further enhanced the Cotton effect and increased the largest |g_abs| to 0.034 at 725 nm, likely due to the enhanced structural rigidity. Our work provides new insights into constructing chiral carbaporphyrinoids with high |g_abs| values.