Ni(II) 10-Boracorrole: An Antiaromatic Porphyrinoid Containing a Boron Atom at the meso-Position

A Ni­(II) 10-boracorrole (2) was obtained from the transmetalation of the corresponding 10-silacorrole with BBr3. The antiaromaticity of 2 was examined by 1H NMR spectroscopy and theoretical calculations. The antiaromatic character of 2 is reflected in a very narrow HOMO–LUMO gap that results in weak and broad absorption bands in the NIR region up to 1800 nm. Furthermore, titration experiments revealed a high Lewis acidity of 2 toward pyridines. Theoretical calculations on 2 indicated the presence of p−π* conjugation, which significantly stabilizes the energy level of its LUMO.