Solid-State Crystallization Behavior of Tetrabenzoporphyrin Organic Semiconductors

The kinetics of the solid-state conversion and crystallization of metal tetrabicycloporphyrins (M-CPs) to metal tetrabenzoporphyrins complexes (M-TBPs) were analyzed by using the Avrami-type equation, and the value of the indices (n) was found to depend on the central atom in M-CP: n = 3 for M = H (TBP), n = 2 for M = Zn, and n = 3 at low temperatures and n = 2 at high temperatures for M = Ni. The heat of crystallization was similar for the M-TBPs, but the activation energy of crystallization varied with the type of central atom. For Ni-TBP and Zn-TBP, metastable phases were first forms, which were then converted into a stable phase, while no such metastable phase was formed in the case of TBP. In addition, the crystallization behavior of TBP was different from that in the thin film state (reported previous study). The crystallization onset temperature varied with the heating rate, although the true temperatures obtained by extrapolating the different heating rates data to zero heating rate were the same. Finally, from the PXRD data, the crystal grains of M-TBPs were found to grow isotropically in the three different directions.