The effect of peripheral halogenation is examined based on analytical
transmission electron microscopy and thermal analyses of two chemical
family structures, specifically the vanadyl-phthalocyanine family (VOPcX:
X = H16, F14.5) and the copper-phthalocyanine family
(CuPcX: X = H16, F16, Cl16,
Cl8Br8), focusing on the process of molecular
changes and crystalline disintegrations. To clarify the molecular
transformations, electron energy-loss spectroscopy (EELS) is applied to
two fluorinated phthalocyanines (VOPcF14.5 and
CuPcF16), by monitoring mass changes as well as energy loss
near edge structures (ELNES). The elemental mass of both
VOPcF14.5 and CuPcF16 remain constant up to 0.5
C·cm−2, except in the case of mass reduction
attributed to oxygen loss occurring in VOPcF14.5. It is
expected that the released oxygen will induce higher radiation damage in
VOPcF14.5. Although mass variation is not observed in
CuPcF16, it is found from ELNES that the π resonant system
of nitrogen is more radiation sensitive than that of carbon. These results
imply that the electron sensitivity in VOPcX is triggered by eliminated
oxygen or, thus, an induced larger empty space, whereas the sensitivity of
CuPcX is dominated only by a large intermolecular empty space resulting in
the following bond alterations. It is also found that the decomposition
temperature (Td) measured by thermal analyses
and the characteristic dose (D1/e) are
exponentially correlated to the “effective molecular
occupancy” (Oe) evaluated as a volume
function of molecules in unit cells. By measuring
Td and/or
Oe, we discuss the durability of peripheral
halogenation with respect to the radiation damage.