meso-Cumulenic 2H-Corroles from meso-Ethynyl-3H-corroles.

Alkynyl-substituted 3H-corrole 9 a was converted to [3]cumulenic 2H-corrole 10 a by treatment with trimethylsilyl chloride (TMSCl), and 1,3-butadiyne-bridged 3H-corrole dimer 11 b was transformed into [5]cumulene-bridged 2H-corrole dimer 12 b by oxidation with PbO . Both 10 a and 12 b were metalated to form Zn complexes 10 a-Zn and 12 b-Zn. The structures of 10 a-Zn and 12 b-Zn show planar conformations with bond-length alternations that are analogous to those of tetraaryl [n]cumulenes. The cumulenic corrole dimers 12 b and 12 b-Zn display large NIR absorption bands in the range of 700-1400 nm (maximum ϵ≈1.0×10  m  cm ) owing to the effective π-conjugation between the two corrole units through the [5]cumulene bridge.