The thermal stability of rod-like phthalocyanines of the general formula R3SiO(SiPcO)(n)SiR3 with n = 1-4 and R = C6H13 was studied by temperature dependent mass spectrometry and X-ray photoemission spectroscopy. The stability of the monomer, dimer, and trimer is high, whereas the tetramer is thermally unstable and therefore cannot be used for thin film preparation by sublimation.