meso-Free BIII Subporphyrins with Electron-donating Groups.

meso-Free BIII 5,10-bis(p-dimethylaminophenyl)subporphyrins were synthesized. They display red-shifted absorption and fluorescence spectra, bathochromic behaviors in polar solvents, a high fluorescence quantum yield (ΦF =0.57), and a small HOMO-LUMO gap mainly due to destabilized HOMO as compared with meso-free BIII 5,10-diphenylsubporphyrin. This subporphyrin serves as a nice precursor of various meso-substituted BIII subporphyrins such as BIII meso-nitrosubporphyrin, BIII meso-aminosubporphyrin, and meso-meso' linked BIII azosubporphyrin dimer. Reactions of meso-free BIII subporphyrins with NBS or bis(2,4,6-trimethylpyridine)bromonium hexafluorophosphate gave meso-meso' linked subporphyrin dimers, often as a major product along with meso-bromosubporphyrins.