Thermal behavior and the solvent effects of ρ-Methoxy Tetraphenylporphyrin (TOMPP), Copper Porphyrin (CuTOMPP), and Nitroporphyrin (CuTOMPP-NO₂)

Chemistry Department, Thammasat University, Pathumtani, 12120, Thailand

Abstract

In this work, ρ-methoxy tetraphenylporphyrin (TOMPP) Copper porphyrin (CuTOMPP) and nitro porphyrin (CuTOMPP-NO₂) are synthesized following Adler Longo method by the reaction of pyrrole with and ρ-anisaldehyde. These compounds have been characterized by UV-Vis, fluorescence spectroscopy and thermogravimetric analysis (TGA). The ρ-methoxy tetraphenylporphyrin (TOMPP) was obtained in 26% yield. Reactions of TOMPP with copper ions gave CuTOMPP in 85% yield. Moreover, the nitration of CuTOMPP gave CuTOMPP-NO₂ in 0.03% yield. The absorption spectra for TOMPP exhibited one S-band (416 nm) and four Q-bands (518, 555, 593 and 650 nm) in dichloromethane solvent. The absorption band of copper porphyrin and nitroporphyrin displays one S band (415 and 423) and two Q bands (range from 550 – 600 nm). When excited to 530-570 nm, the fluorescence spectra show only one emission band at 645-654 nm for TOMPP and copper complexes. The results confirmed the solvent effect on the electronic absorption as found a small red shift from 414 nm (chloroform) to 417 nm (ethyl acetate) for TOMPP. The thermal behaviors including the possible phase transition of porphyrins were studied during the heating process at temperature of 298-973 K. Copper complexes exhibits the thermal stability from 653.3 K, which is slightly lower than that of the free base porphyrin ligand (TOMPP 703.9 K).