meso-Nitro- and meso-Aminosubporphyrinatoboron(III)s and meso-to-meso Azosubporphyrinatoboron(III)s

meso-Nitrosubporphyrinatoboron(III) was synthesized by nitration of meso-free subporphyrin with AgNO₂/I₂. The subsequent reduction with a combination of NaBH₄ and Pd/C gave meso-aminosubporphyrinatoboron(III). meso-Nitro- and meso-amino-groups significantly influenced the electronic properties of subporphyrin, which has been confirmed by NMR and UV/Vis spectra, electrochemical analysis, and DFT calculations. Oxidation of meso-aminosubporphyrinatoboron(III)s with PbO₂ cleanly gave meso-to-meso azosubporphyrinatoboron(III)s that exhibited almost coplanar conformations and large electronic interaction through the azo-bridge.