Porphyrin compounds are widely known to play an important role in biological systems. We have recently found that tetrabenzoporphyrin (
Shinji Aramaki, Jin Mizuguchi, "Crystal and Electronic Structure of Metal-Free Porphyrin: A New Material for Organic FET" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP20), 2004, pp 514 - 519, https://doi.org/10.2352/ISSN.2169-4451.2004.20.1.art00001_2