Study of the thermal decomposition of tetrapyrazino[2,3-b]indoloporphyrazine films

Copper and metal-free tetrapyrazino[2,3-b]indoloporphyrazine films are prepared by vacuum thermal evaporation (TE) and Langmuir–Blodgett (LB) techniques. The spectroscopic properties of the thermally evaporated and Langmuir–Blodgett tetra(5-n-amyl-8-tert-butyl-2,3-pyrazino[2,3-b]indolo)porphyrazinato copper(II) and tetra(5-n-amyl-8-tert-butyl-2,3-pyrazino[2,3-b]indolo)porphyrazine films have been investigated and compared using UV–vis, X-ray photoelectron spectroscopy (XPS), and matrix-assisted laser desorption ionization time of flight (MALDI-TOF) techniques. UV–vis spectroscopy confirms decomposition of the tetrapyrazino[2,3-b]indoloporphyrazine's main macrocyclic ring structure, as evidenced by the disappearance of the Q band. The C 1s XPS spectra show that the area ratios between the fitted peaks (C_285.5 eV/C_287.2 eV) are 2.03 and 1.47 for LB and thermally evaporated films, respectively. The difference may be due to the decomposition of pyrrole rings and loss of alkyl groups during thermal evaporation. MALDI-TOF measures lower masses with a broader distribution for the thermally evaporated films compared to the LB films, which is caused by thermal decomposition of the tetrapyrazino[2,3-b]indoloporphyrazine molecules.