Crystal and Electronic Structure of Metal-Free Porphyrin: A New Material for Organic FET

摘要

Porphyrin compounds are widely known to play an important role in biological systems. We have recently found that tetrabenzoporphyrin (i.e. metal-free porphyrin: BP) exhibits an excellent FET characteristic. BP is usually synthesized via metal salts such as Zn and Cd. Because of this, FET characteristics are rather limited due to incur-porated metallic impurities. However, FET performance is greatly improved when BP is directly prepared by thermal decomposition from its precursor (CP) that is free from metals. The present paper deals with crystal structure of both BP and CP as well as their electronic characterization. Special attention has been focused on the comparison in electronic structure between BP and metal-free phthalo-cyanine (H_2Pc). Both compounds are quite similar in molecular conformation and arrangement. Nevertheless, the crystallographic parameters are quite different. Furthermore, their polarized reflection spectra measured on single crystals are also significantly different.